The IEC 61000-4-30 Class A standard defines the measurement methods, time aggregation, accuracy, and evaluation, for each power quality parameter to obtain reliable, repeatable and comparable results between various brands and models of PQ instruments and systems.
IEC 61000-3-30 Class A Edition 2
IEC 6100-4-30 Class A Edition 2 standardizes the measurements of:
Power frequency
Supply voltage magnitude
Flicker (by reference to IEC 61000-4-15)
Voltage dips/sags and swells
Voltage interruptions
Supply voltage unbalance
Voltage harmonics, and interharmonics (referenced to IEC 61000-4-7)
Mains signaling voltage
Rapid voltage changes
Magnitude of current
Current harmonics and interharmonics (referenced to IEC 61000-4-7)
Current unbalance
IEC 61000-4-30 Edition 3 Introduced new measurements definitions and PQ parameters.
“This third edition cancels and replaces the second edition published in 2008. This edition constitutes a technical revision”.
Rapid voltage changes
Flicker class F1
Magnitude of the current
Current unbalance
Current harmonics (by reference to IEC 61000-4-7)
Current interharmonics (by reference to IEC 61000-4-7)
Additional changes in harmonic parameters from IEEE 519 2014
The number of harmonics to be evaluated. In many application, 50 harmonics are not enough and modern DC to AC inverters used in Wind and Solar generation have significate harmonic component up to the 100th.
Recording resolution – the latest edition of the IEEE 519 requires a daily and weekly harmonic evaluation of both voltage and current at 150/180 cycles (~3sec) resolution per phase. An edition 3 compliant instrument must record this data and prepare a report from the instrument.
Why these revised standards are important to electric utilities?
1. Rapid Voltage Change (RVC) parameter captures voltage changes (sags) that can be disruptive to some loads without exceeding the standard of +/- 5% voltage change limit. An instrument that does not make RVC measurements will miss these events. So a utility may receive customer complaints (most common is light flickers) and not have any data to find the source of the complaint. (most common is large motor starts or other sudden load or distributed generation switching. (tripping)
2. The Edition 3 revision transfers the responsibility for measurement methods continue in this standard, but responsibility for influence quantities, performance, and test procedures are transferred to IEC 62586 -1 and -2.
Part 1, namely IEC 62586-1, was constructed to define a comprehensive PQ device product standard, coined within as PQIs. The standard outlines safety, electromagnetic compatibility (EMC), climatic, and mechanical requirements, and refers to IEC 62586-2 for functional aspects. These requirements serve to ensure the instrument’s robustness will be suitable for its installation within the severe environments of a power station or substation.
Part 2, IEC 62586-24, defines the functional tests cited in the first part of the series. These tests are intended to comprehensively verify the PQ measurement methods outlined in 4-30. This chapter was established to provide traceable and repeatable procedures to verify the compliance of each PQ metric outlined in 4-30. This firstly addresses the main shortcoming of 4-30 and ensures better method adherence between PQ meter manufacturers. Additionally, the standard allows regulatory laboratories adhering to ISO/IEC 170255 to issue conformance reports and certificates according to IEC 62586-1 or IEC 62586-2 (with compliance to IEC 62586-2 meaning compliance to IEC 61000-4-30). The latter provides PQ meter manufacturers a way to provide internationally recognized compliance for the entire scope of PQI requirements.
3. To help ensure accurate PQ metrics in the harsh installation environment of a power station or substation, a number of electromagnetic compatibility (EMC) and influence quantity tests were also added to the scope of the IEC 62586 series.
“IEC 62586-2:2013 specifies functional tests and uncertainty requirements for instruments whose functions include measuring, recording, and possibly monitoring power quality parameters in power supply systems, and whose measuring methods (class A or class S) are defined in IEC 61000-4-30. This standard applies to power quality instruments complying with IEC 62586-1. This standard may also be referred to by other product standards (e.g. digital fault recorders, revenue meters, MV or HV protection relays) specifying devices embedding class A or class S power quality functions according to IEC 61000-4-30. These requirements are applicable in single, dual- (split phase) and 3-phase a.c. power supply systems at 50 Hz or 60 Hz.”
4. Environmental impact on the instrument from a laboratory environment. (25 Degrees C to a substation environment 40 Degrees C + ) is now part of the requirement of this standard. Detailed measurement procedures for Harmonics including to the 100th are included. Reporting of the harmonics to IEEE 519-2014 with harmonic limits specified for 1 and 1 week are included.
5. Detailed measurement procedures for Harmonics including to the 100th are included.
6. Reporting of the harmonics to IEEE 519-2014 with harmonic limits specified for 1 and 1 week are included.
All of these issues can be defined as IEC 61000-4-30 Class A, Edition 3 compliant.
Published by Jalal Ibrahimov1, Tural Aliyev2, Ilkin Marufov3, Nijat Mammadov4, Azerbaijan State Oil and Industry University ORCID: 3. 0000-0002-3143-0113; 4. 0000-0001-6555-3632
Abstract. The widespread use of electric automobiles will lead to significant changes in instantaneous consumption values and the mechanisms that govern this consumption. Electricity demand will increase sharply and there will be fluctuations in the networks. The only way to cope with this problem is to switch to smart networks. This article examines and economically analyses the method of switching from a vehicle to a network, which is considered to be used to solve the problem of fluctuations caused by the integration of renewable energy sources into the network. For this purpose, unlike other studies in the literature, a simulation study was conducted that took into account both the battery life of the car and the driver’s behavior. The research to be done in smart networks and renewable energy sources should not be accepted only for home consumers. In terms of competitiveness, industrial consumers need to choose devices that support smart grids when developing and planning their systems. Researches on energy quality and vehicle-to-grid (V2G) is very important in this regard. In addition to engineering objectives, electric automobiles should also be looked at from an economic point of view, such as the benefits and costs they can provide due to the level of vertical integration.
Streszczenie. Powszechne wykorzystanie samochodów elektrycznych doprowadzi do znaczących zmian w wartościach chwilowego zużycia energii i mechanizmach rządzących tym zużyciem. Zapotrzebowanie na energię elektryczną gwałtownie wzrośnie, a w sieciach wystąpią wahania. Jedynym sposobem poradzenia sobie z tym problemem jest przejście na sieci inteligentne. W artykule zbadano i poddano analizie ekonomicznej sposób przejścia z pojazdu do sieci, który uważa się za stosowany w celu rozwiązania problemu wahań spowodowanych włączeniem do sieci odnawialnych źródeł energii. W tym celu, w odróżnieniu od innych badań dostępnych w literaturze, przeprowadzono badanie symulacyjne, w którym uwzględniono zarówno czas pracy akumulatora samochodu, jak i zachowanie kierowcy. Badania, jakie należy przeprowadzić w zakresie inteligentnych sieci i odnawialnych źródeł energii, nie powinny być akceptowane jedynie w przypadku odbiorców domowych. Jeśli chodzi o konkurencyjność, konsumenci przemysłowi muszą wybierać urządzenia obsługujące inteligentne sieci podczas opracowywania i planowania swoich systemów. Badania nad jakością energii i pojazdem do sieci (V2G) są w tym względzie bardzo ważne. Oprócz celów inżynieryjnych na samochody elektryczne należy patrzeć także z ekonomicznego punktu widzenia, np. korzyści i kosztów, jakie mogą zapewnić ze względu na poziom integracji pionowej. (Rozwiązanie problemów związanych z integracją odnawialnych źródeł energii: integracja pojazdów elektrycznych z sieciami dystrybucyjnymi)
Keywords: Vehicle-to-Grid, energy management, electric vehicles, PV charging, renewable energy, distribution network, V2G Słowa kluczowe: Vehicle-to-Grid, zarządzanie energią, pojazdy elektryczne, ładowanie PV, energia odnawialna, sieć dystrybucyjna, V2G
1.Introduction
Now the whole world is making a rapid transition to renewable energy. But renewable energy systems also have many negative aspects on the network. Generally, solar and wind are the first sources of renewable energy sources. However, these sources are variable, that is, if the wind blows and the sun shines in the air, electricity is generated. On the other hand, the demand in the electricity network is very variable for every hour of the day. Electricity demand is higher during the day, and lower at night than during the day. In this case, it is not always possible to rely on renewable energy plants due to weather conditions. These power plants must also be integrated into storage systems. There are many energy storage methods. But, of course, these methods cannot be applied everywhere due to regional and financial problems, so electric vehicles can be used as a storage tool.
The number of electric vehicles on the roads is increasing every day. Along with this increase, the demand for electricity will naturally increase. Every electric vehicle on the road needs electricity to be charged. Of course, this electricity also needs to be generated from clean energy sources. Therefore, electric vehicles can be used as a complement to renewable energy plants. It can feed the network when the demand for electric vehicles is full when it is full, and it can be stored in electric vehicles when the demand is low, and it can be renewed when the demand is low [1].
Today, the increase in the number of electric vehicles creates a real opportunity for grid balancing. This opportunity can be used to help balance the electrical system and manage local ecosystems by being managed with Vehicle-to-Grid (V2G) solutions. Vehicle to Grid is a system in which plug-in electric vehicles (EV) are connected to the energy grid by transmitting electricity back to the grid or by reducing the charging rates to realize demand-side services. The basic concept of vehicle-to grid demonstrated in the Figure 1.
Fig.1. Vehicle-to-Grid conception
The Vehicle-to-Grid (V2G) system enhances electric vehicles’ storage capacity, enabling them to store or discharge electricity from renewable sources. This flexibility facilitates the integration of numerous renewable energy sources. However, additional studies are necessary to address the increased electricity consumption resulting from widespread V2G adoption. Countries need to prepare for this surge in demand. The escalating need for energy presents inevitable challenges on the production side. Renewable energy sources offer environmentally friendly solutions to augment production but come with their own set of issues. To efficiently provide services, networks must accurately estimate production volumes from alternative sources. Hybrid renewable energy applications serve as eco-friendly solutions designed for this purpose.
Post the Fukushima incident, there has been a rapid increase in the demand for alternative energy sources, with solar and wind energy being the most prevalent. However, reliability and cost pose challenges, influenced by seasonal conditions and high initial installation costs. The research aims to explore the integration of these sources into the network and assess the benefits of employing the Vehicle-to-Grid (V2G) method in conjunction with these renewables. An energy management system model combining V2G and various renewable sources has been developed and explored for different scenarios, highlighting the advantages V2G offers in renewable energy-dependent networks [2, 3].
2. Materials and methods
Vehicle-to-network power transmission. The V2G method is a new method developed in recent years. This method has many important mechanisms, such as meeting high energy demand or balancing the cost of generating electricity.
The number of electic automobiles in the transport system of many countries is growing rapidly. These cars must be connected to the mains to charge their high-capacity batteries. The problems that can arise from this type of simultaneous connection have been discussed. The fact that these cars were generally stationary during the day gave rise to the idea of using their batteries. V2G is a method that uses EA batteries to store energy and aims to create a distributed power source. Using this method, it seems possible to solve the problems of reliability of renewable energy sources in a cooperative way. V2G hybrids can be ancillary to renewable energy systems [4].
Mathematical model and computational method. The generating capacity of the network is determined by deducting the cost of production from the production of renewable energy sources and auxiliary sources. Quantity of production “P” at any “t” time calculated by:
.
Here: PG-grid production, PW-wind power generation, PS-solar power generation, PA-auxiliary production. The PC-parameter is used to indicate consumption. There are various methods for modeling wind energy, which is a variable production method. PW can be obtained using the Weibull probability distribution.
.
Here: v-wind speed, vci-wind speed at which the turbine isstarted, vco-wind speed at which the turbine is stopped, vR-wind speed at rated power. Other parameters include k: smoothing factor and λ-is a ratio used for scaling. The measured wind energy data can be approximated to the Weibull probability distribution. Different probability distributions can also be used for production and consumption data from solar energy. Instead of distributed methods, measured real data values from all sources can also be used. The contribution of backup sources varies depending on the source selected. If V2G is used, this structure is seen as a participatory system, and production capacity depends on two factors. These are; The SOC status of EA batteries and the probability of EA connecting to V2G (POP). There are several situations that affect the value of POP. The first is the importance and frequency of use of the car. The other is the motivation of vehicle owners to participate in the system. Incentive-based mechanisms can be used to increase the value of POP in an energy management system. As with DSM systems, rewards can increase the desire to participate. Presumably, unlike the POP value expressed in the range [0-1], the SOC value is expressed as a percentage (0: empty, 100: full).
.
A block diagram of a calculation method using a mathematical model is shown in Figure 2.
Fig.2. Proposed energy management system model
In the computational method, forecasting was used in the available energy capacity method to determine V2G production. This method first determines the probability of participation having the same value for all vehicles. If a different probability value is used for each vehicle, the computational complexity increases dramatically. Using the total participation probability, the share distribution can be simplified to the binomial distribution. Finally, the available energy capacity is calculated by grouping the vehicles into different groups. The SOC features of the EA are also taken into account in order to make a better assessment of the calculation method [5, 6, 7, 8].
Vehicle-to-network simulation research. In the simulation study, the POP and SOC values were taken as random values due to their uncertainties. Random POP and SOC values are given equally to each EA owner. Due to these values, the participation of vehicles in V2G is formed. The study examines three scenarios in which renewable energy sources contribute to the grid to varying degrees. Production profiles of energy sources were created using the total capacity values in Table 1 [9, 10].
Table 1. Sources used and total capacity values
.
Fig.3. Daily production profiles of wind turbines and PV panels
Figure 3 shows the daily production profiles of these sources. Production of PV panels peaks in the afternoon, and for the rest of the day, production is almost non-existent for some time. Similarly, wind energy production exhibits a non-permanent production behavior. It is not possible for the network to create a reliable power supply using only these two sources.
Figure 4 shows a description of the network’s total electricity generation for the day.
Fig.4. The daily total production profile of the network we show is an example
In many studies in the scientific literature, the probability of EA participating in V2G has been defined as a single value. Because such a hypothesis does not accurately reflect real life, each EA was given a separate opportunity to participate. The probabilities of V2G participation were determined by the intervals given in Table 2 and by scenario type.
Table 2. The probable value ranges for EA’s and V2G contributions
.
The parameters given in Table 3 are used to determine the production of renewable energy sources for different scenarios.
Table 3. Rates of reduction in production for different scenarios
.
Use of small amounts of renewable energy sources. In this scenario, renewable energy sources are likely to be more limited. The reason for this restriction may be a seasonal condition or a temporary decrease in production. As a result, in such a scenario there is a maximum and stable requirement for V2G supply. The likelihood of EA participating in V2G has also been kept high for this purpose. Figure 5 shows the impact of V2G on the network in this scenario. A more balanced production profile was obtained using V2G.
Fig.5. Impact of V2G on the network when using small amounts of renewable energy sources
Use of large amounts of renewable energy sources. In this scenario, the production of renewable energy sources is assumed to be higher than in the previous scenario. EA owners have an average motivation to participate in V2G, according to Table 2. When Figure 6 is examined, it is seen that V2G is able to balance the production profile of the network as in the previous scenario.
Fig.6. Impact of V2G on the network when large amounts of renewable energy sources are used
Use of very high amounts of renewable energy sources. In the third scenario, the contribution of energy from renewable energy sources to the grid is assumed to be very high. In such a situation, the desire to participate in V2G is kept low to avoid overproduction, and opportunities to participate are identified accordingly. As shown in Figure 7, the presence of a small amount of V2G further increased production. Due to the predominance of renewable energy sources, the network has a wavy production profile. The small contribution of V2G is very similar to the absence of V2G in the system [11, 12].
Fig.7. Impact of V2G on the network when very high amounts of renewable energy sources are used
Economic analysis and evaluation. Production using fossil fuels is generally undesirable because it is harmful to the environment. However, based on the structure of public finance, production costs are extremely important for many countries. Initial investment and maintenance costs are not taken into account when comparing V2G and fossil fuel solutions. Because taking into account the initial investment costs gives V2G an unfair advantage. In fact, the electric automobiles that make up V2G’s initial investment cost is purchased by car owners, and maintenance costs are also paid by car owners. The costs of both production methods are compared in Table 4 [13].
The most important cost area of V2G is the battery. The supply of these systems is limited by battery technology, battery health, and SOC. In order to avoid possible voltage problems, the SOC value in cars participating in the V2G system must be more than 20 percent. The main problem with the EA produced to date is that the driving distances of vehicles are not very long. No EA owner wants their car to be kept at a low SOC value by the V2G system and starts their journey that way. Therefore, in a V2G system, it is necessary to prevent SOC values from falling below 50 percent. However, this criterion may reduce the contribution of V2G to the system. Table 5 summarizes how SOC values should be interpreted for a V2G system [14].
Table 4. Comparison of the cost of fossil fuel production with V2G
.
Table 5. Meaning of SOC values for V2G
.
EA batteries today consist of electrochemical layers. The batteries have various problems due to wear, overheating, charging, and discharging. Frequent charging and discharging processes accelerate deterioration. However, even without the V2G system, the car’s battery wears out and runs out. Only the additional effects of V2G on battery life should be considered. In addition, it has been observed that the charging and discharging process at lower average SOC values prolongs battery life. As a result, an intelligent power management system must drive the cars involved in V2G, taking into account the SOC values. This section provides an economic analysis of V2G hybrid renewable energy systems and explores V2G integration. V2G is an environmentally friendly solution that promises to maximize the benefits of a hybrid renewable energy system. Renewable energy sources, such as wind and solar energy, cannot provide uninterrupted production due to external conditions. V2G can be used to overcome this continuity problem in production. However, EA batteries in the V2G system must be subjected to charging and discharging processes that often reduce their life. Despite the additional cost of the battery, a V2G system is both more economical than residual fuel alternatives and less harmful to the environment. Another important factor that will affect the success of the V2G system is the participation of vehicle owners. In cases where motivation is low, participation can be increased by using an incentive-based mechanism [15].
3. Conclusion
The study realized for the three scenarios in which renewable energy sources contribute to the grid to varying degrees. Production profiles of energy sources were created using the total capacity values that given by authors. In the applied example, it is assumed that only wind and solar energy sources are used in the network. Results were obtained according to three situation that indicated in the body of article.
1. In the scenario of small amounts of renewable energy sources because of the restriction of a seasonal condition or a temporary decrease in production, there is a maximum and stable requirement for V2G supply. The likelihood of EA participating in V2G has also been kept high for this purpose. A more balanced production profile was obtained using V2G.
2. In the scenario of many renewable energy sources, the production is assumed to be higher than in the previous scenario. EA owners have an average motivation to participate in V2G. When simulation analyzed, it is seen that V2G is able to balance the production profile of the network as in the previous scenario.
3. In the third scenario, the contribution of energy from renewable energy sources to the grid is assumed to be very high. In such a situation, the desire to participate in V2G is kept low to avoid overproduction, and opportunities to participate are identified accordingly. Due to the predominance of renewable energy sources, the network has a wavy production profile. The small contribution of V2G is very similar to the absence of V2G in the system.
REFERENCES
[1] A. Panday and H. O. Bansal, “Green Transportation: Need, Technology and Challenges”, Int. J. Global Energy Issues, Inderscience publishers, Vol. 37, No. 5/6, pp. 304-318 [2] A. Briones, J. Francfort, P. Heitmann, M. Shey, S. Shey and J. Smart, “Vehicle-to-grid (V2G) power flow regulations and building codes review by the AVTA”, INL/EXT-12-26853, September 2012 [3] R. Sioshansi and P. Denholm, “The value of plug-in hybrid electric vehicles as grid resources”, Energy Journal, vol. 31, no.3, paper no. 01/2010 [4] A. B. Rolufs, “Kansas City Plug-In Electric Vehicle Demonstration Project”, Missouri Transportation Institute, Missouri university of science and engineering [5] T. Morgan, “Smart grids and electric vehicles: Made for each other?”, Summit Int. Transport Forum, on Seamless Transport: Making Connections, Leipzig, Germany, discussion paper no. 2012-02, OECD 2-4 may 2012 [6] S. Morash, “Vehicle to grid: plugging in the electric vehicle”, Senior Capstone Projects, paper 200 [7] W. Kempton and V. Udo, Ken Huber, K. Komara, S. Letendre, S. Baker, D. Brunner and N. Pearre, “A test of vehicle-to-grid (V2G) for energy storage and frequency regulation in the PJM system”, nov. 2008 [8] S. Han, S. Han, K. Sezaki, Development of an optimal vehicleto-grid aggregator for frequency regulation, IEEE Trans. Smart Grid 1 (1) 65-72, 2010 [9] C. Quinn, D. Zimmerle, T.H. Bradley, The effect of communication architecture on the availability, reliability, and economics of plug-in hybrid electric vehicle-to-grid ancillary services, Journal of Power Sources 195 (5) 1500-1509, 2010 [10] M.A. Fasugba, P.T. Krein, Cost benefits and vehicle-to-grid regulation services of unidirectional charging of electric vehicles, in: Proc. IEEE Energy Conversion Congress and Exposition (ECCE 2011), Phoenix, USA, Sept. 17-22, pp. 827-834, 2011 [11] A. Papavasiliou, S.S. Oren, Supplying renewable energy to deferrable loads: Algorithms and economic analysis, in: Proc. IEEE Power and Energy Society General Meeting, Minneapolis, USA, pp. 1-8 July 25-29, 2010 [12] A. Millner, “Modeling lithium ion battery degradation in electric vehicles,” 2010 IEEE Conf. Innov. Technol. an Effic. Reliab. Electr. Supply, CITRES 2010, pp. 349–356, 2010 [13] M. Yilmaz and P. T. Krein, “Review of Battery Charger Topologies , Charging Power Levels , and Infrastructure for Plug-In Electric and Hybrid Vehicles,” vol. 28, no. 5, pp. 2151–2169, 2013 [14] D. P. Tuttle, R. L. Fares, R. Baldick, and M. E. Webber, “PlugIn Vehicle to Home (V2H) duration and power output capability,” 2013 IEEE Transp. Electrif. Conf. Expo, pp. 1–7, Jun. 2013 [15] “Global ev outlook: Understanding the electric vehicle landscape to 2020”,www.iea.org, 2017
Source & Publisher Item Identifier: PRZEGLĄD ELEKTROTECHNICZNY, ISSN 0033-2097, R. 100 NR 9/2024. doi:10.15199/48.2024.09.08
Published by 1. Anatolii SEMENOV1, 2. Stanislav POPOV1, 3. Serhii YAKHIN1, 4. Bauyrzhan YELEUSSINOV2, 5.Tamara SAKHNO1, Poltava State Agrarian University (1), Branch of JSC «NCPD Orleu» Institute of professional development in Kyzylorga region (2) ORCID: 1. 0000-0003-3184-6925; 2. 0000-0003-2381-152X; 3. 0000-0002-0042-0844; 4. 0009-0005-0552-6794; 5. 0000-0001-7049-4657
Abstract. To determine the photobiological safety of UV lamps, the following measurements were carried out: spectral irradiance, total actinic irradiance in the wavelength range of 200-400 nm, and irradiance in the UVA range (320-400 nm). These parameters were measured using the optical radiation system OST-300. The photobiological safety of LUF 40-1, LE 15 lamps and their radiation risk group are established in accordance with EN 62471. The levels of UV radiation generated by LE 15 low pressure discharge lamps at a distance of 0.25 m belong to the high risk group (GR3), and LUF 40-1 – in the group of insignificant risk (GR1). Calculations and recommendations on safe radiation doses when using lamps in electrotechnical systems of photobiological influence are given
Streszczenie. W celu określenia bezpieczeństwa fotobiologicznego lamp UV wykonano pomiary: natężenia promieniowania spektralnego, całkowitego natężenia promieniowania aktynicznego w zakresie długości fal 200-400 nm oraz natężenia promieniowania w zakresie UVA (320-400 nm). Parametry te mierzono za pomocą optycznego systemu promieniowania OST-300. Bezpieczeństwo fotobiologiczne lamp LUF 40-1, LE 15 oraz ich grupa ryzyka radiacyjnego są określone zgodnie z normą EN 62471. Poziomy promieniowania UV generowane przez niskoprężne lampy wyładowcze LE 15 w odległości 0,25 m należą do grupy wysokiego ryzyka (GR3), a LUF 40-1 – w grupie ryzyka znikomego (GR1). Podano obliczenia i zalecenia dotyczące bezpiecznych dawek promieniowania przy stosowaniu lamp w elektrotechnicznych układach oddziaływania fotobiologicznego. (Ocena niebezpieczeństwa stosowania lamp ultrafioletowych w instalacjach elektrycznych)
Ultraviolet radiation is one of the important environmental factors that significantly affect the human body [1]. Humans are increasingly being exposed to ultraviolet rays due to the thinning of the ozone layer and its widespread use in sterilization processes, especially against the SARS-CoV-2 virus [2].
The state and environmental parameters of ultraviolet radiation are essential for its life in the inactivation of bacteria [3], irradiation of surfaces [4] and stimulation of processes [5]. In the process of evolution, under the influence of solar ultraviolet radiation in the human body, a whole complex of photobiological reactions has developed, both positively and negatively affecting its vital activity [6]. UV irradiation at doses of 10-15 J/m2 can stop the division of 90% of cells. Ultraviolet rays of different spectral ranges cause changes in cells that affect vital functions: growth, division, heredity. Therefore, radiation in the range from 320 to 400 nm causes slight erythema in humans, and radiation in the wavelength range from 290 to 320 nm and less causes burns [1]. The danger of ultraviolet radiation is also because a person does not have a sensory organ that could directly react to ultraviolet radiation.
Despite the study of the effects of UV radiation as a powerful hygienic and therapeutic factor, systematic studies of the beneficial effects of monochromatic radiation of various wavelengths have not yet been carried out. At present, there are only attempts to link the variety of beneficial effects of UV radiation with one, rather well studied function and to attribute to it the cause of integral beneficial effects [1]. The established factors of influence [7, 8] of UV radiation on cells of living organisms require detailed research and analysis to determine the photobiological safety of UV radiation on humans, depending on the spectrum and dose of radiation in various systems of ultraviolet action [9, 10]. Until recently, it was believed that UV radiation in the spectral range of 290-400 nm is useful says [1] and was considered as one that activates the defense mechanisms of the human body [11, 12].
Approximately 95% of all solar UV radiation reaching the Earth’s surface is UV-A light (320-400 nm), which causes oxidative stress and the formation of DNA photoproducts in skin cells [13]. UVA radiation does not play a significant role in the negative impact on living objects, since it is poorly absorbed by DNA cells [14]. Risk-benefit analysis of exposure to solar ultraviolet radiation is widely used in the literature [15, 16]. A review by author [17] presents a mechanistic consideration of the wavelength dependence for UVR-specific mutations and substantiates the suggestion of UVA signature mutation in addition to UV signature mutation.
Recent studies by many authors have shown that UVA radiation creates a number of negative consequences for the human body, which can lead to serious structural and functional damage to the skin, and create mutagenic effects [18]. It is also necessary to take into account the effect of UV radiation on the retina and other components of the organs of vision [19]. UV radiation (even mild – UV-A) can lead to serious damage to the visual apparatus, since the receptors of vision do not feel its influence.
One of the health problems around the world associated with ultraviolet light is cataracts [20]. It especially often occurs in rural residents who spend a lot of time in unshaded areas [21]. More than a hundred scientific papers on the impact of artificial light sources and natural UV radiation of the sun on human health have been analyzed in the studies of the international organization WHO [7].
Multiple experimental confirmations have negative effects and the evidence continues to grow. UVA radiation penetrates deeper into the skin than UVB and causes photoaging. The influence and mechanism of action of ultraviolet B (UVB) on melanin synthesis and premature aging in cells. Herewith, the melanin content first increased, and then decreased with increasing UVB exposure [22].
The harmful effects of UV-B radiation on photosynthesis and photosynthetic productivity of plants are given in [23]. UV-B radiation has been shown to damage the photosynthetic apparatus of green plants in many place [24].
The misconception that high-intensity UV-A exposure from tanning devices is safe and not associated with melanoma is being challenged. More recent data from experimental studies induced in the review [18] provide strong evidence for a strong association between UV-A and the risk of melanoma. UVA is a complete carcinogen that may play a key role in both the onset and progression of melanoma.
In research [25], was carried out that using ultraviolet lamps on devices intended for UV curing of artificial nail coatings, which are widely used in manicure salons all over the world. The photobiological safety of these devices has been reviewed in the dermatological literature [26], where two cases of non-melanoma skin cancer on the dorsum of the hand were observed in women with previous exposure to UV nail lamps. Doctors say that UV lamps for manicure can be compared to tanning devices – tanning beds, and suggest that they may also pose a risk factor for developing skin cancer [27].
The most favorable direction in the study of the photobiological safety of lamps and lamp systems is the analysis of UV systems used to obtain artificial irradiation in tanning salons, since there is regulatory documentation in EN 60335–2–27 [28] and IEC 61228 [29] and the necessary equipment allows a number of studies in this direction. In addition, a number of studies have shown that in most tanning salons, the irradiance level is above the safety limits and the ratio of UVB/UVA fluxes is significantly different from natural sunlight.
Requirements for the radiation of lamps used in photobiological systems are established in EN 60335–2–27 [28] and IEC 61228 [29], which presents the specifications of the recommended photobiological safety practice for lamps – classification and labelling of risk groups. These specifications include a risk analysis of exposure thresholds for exposure to ultraviolet radiation and subsequently adopted as international standards by the International Electrotechnical Commission (IEC). The total effective surface radiation flux density, which is estimated in accordance with the spectrum of erythema action, should be no more than 0.7 W/m2 . In addition, according to EN 60335-2-27, the radiant flux density in the spectral range of 280-400 nm should be no more than 0.3 W/m2 . Appliances for domestic use must have a total effective surface radiation flux density that does not exceed 0.15 W/m2 . The UVB/UVA ratio shows how much of the UVB region radiation, assessed by the weight function of the carcinogenic hazard, falls on the UVA region radiation. It is known that high doses of UVB radiation cause burns, so it should be limited. Erythema-weighted irradiance and the ratio ЕUVB/ЕUVA, assessed by the weight function of the carcinogenic hazard of radiation, are the main parameters of lamps, and they are communicated to consumers by labelling with a UV code. In various systems of photobiological action, depending on the design and purpose, UV lamps with a radiation spectrum are used, which significantly differs from the UV spectrum of the Sun.
In most cases, low-pressure discharge lamps are used [30]. The parameters of some types of lamps are given in Table 1.
Studies carried out by the authors [31] have shown that the level of irradiation, which is created by low-pressure discharge lamps in the UVB range, is predominantly lower, and the irradiation in the UVA range is much higher than natural. In [32, 33] it was shown that the erythema-weighted irradiation of ultraviolet systems exceeded the established requirements of European standards.
According to IEC 61228 [29], information that must be provided by the manufacturer, upon request, including data on the spectral distribution of radiation depending on the product in the form of: spectral power of radiation, or spectral intensity, or spectral illumination and power conversion factor into radiant flux. Manufacturers are also required to provide information on the potential hazards associated with UV and optical radiation [34] sources upon request.
Table 1. Characteristics of low-pressure discharge lamps
.
The need to check UV lamps used in various photobiological systems for irradiation and stimulation of processes is caused by the discrepancy between the real parameters of the lamps and the requirements of international standards. The need for research is also due to the appearance of a large number of household UVaction devices to combat viral diseases, which are not monitored for compliance with photobiological safety requirements.
Materials and methods of research
Determining the risk group of lamp radiation and studying their photobiological safety in accordance with EN 62471 was the aim of this work [35]. Research objects:
1. Erythema lamps LE 15. Allow to receive additional erythema radiation in areas where the daylight hours are shorter or where there is no natural solar radiation at all. Erythema lamps are used at agricultural enterprises to reduce ultraviolet starvation of poultry and animals.
2. Lamp ultraviolet LUF 40-1. Low-pressure discharge lamps of the LUF type are intended for operation in various irradiation installations using the photochemical and biological action of ultraviolet radiation in the 300-420nm spectral region. Lamp LUF-40 has found wide application in the printing industry.
On fig. 1 shows the markings on the samples of the studied lamps.
Fig.1. Samples of the tested lamps
Standardized methods for assessing and classifying the risks of ultraviolet blue and infrared radiation are given in the SIE S009 standard, and then adopted by the International Electrotechnical Commission in the IEC 61228 [29].
The significance function for assessing the danger of actinic UV radiation for the skin and eyes is presented in EN 62471 [35]. In EN 62471 limit values (RG) of irradiance are established, which, when using electrical devices and lamp systems, must not be exceeded. For UV lamps, the exposure limits for various groups of photobiological risks are given in table 2.
EN 62471 [35] is the only regulatory document by which the safety of UV lamps can be assessed. Spectral irradiance measurements E(λ) and calculations of the total actinic irradiance ЕUV in the wavelength range 200–400 nm and irradiance ЕUVA in the UVA range (320–400 nm) were carried out according to the method described in IEC 61228 [29] and EN 62471 [35]. The measurements were carried out using an OST-300 optical radiation system [30], which contains software for calculating the total actinic irradiance and irradiance in individual spectral ranges [36]. The program also allows you to calculate the exposure limits and the risk group.
Table 2. Exposure limits for different groups photobiological risks
.
Results of the research
The results of measuring the spectral irradiance (W/(m2.nm) of LUF 40-1 and LE 15 lamps in the wavelength range of 200-500 nm are shown in figure 2.
Fig.2. Spectral irradiance of lamps of type LUF 40-1(a) and LE 15(b)
In the studied lamps LUF 40-1 and LE 15 on the marking and in the additional information provided in the technical specifications for lamps LUF 40-1 and LE 15 there is not enough information to determine the equivalence code (UV code) according to IEC 61228 [34]. To determine the codes, it was necessary to measure and calculate the following indicators: total effective erythemal UV irradiation in the spectrum range of 250-400 nm; effective irradiation by the function of significance and carcinogenic – dangerous irradiation in the UVA (λ>320 nm) and UVB (λ<320nm) spectrum ranges; determination of the ratio of effective irradiance (irradiance) ЕUVB/ЕUVA.
The calculations were carried out in accordance with the requirements of IEC 61228 [29]. The calculation results are summarized in table 3.
Table 3. Calculation results of effective irradiance to determine the UV code of lamps according to IEC 61228
.
UV – code of the LUF 40-1 lamp: 40-O-4.0/3.6, where 40-O is a lamp without a reflector, with a power of 40 W; 4.0 – effective erythemal irradiance at a distance of 0.25 m in the spectral range of 250–400 nm; 3.6 – ЕUVB/ЕUVA.
UV code of the LE 15 lamp: 15-O-1470.0/167.8, where 15-O is a lamp without a reflector, with a power of 15 W, 1470.0 is an effective erythemal irradiance at a distance of 0.25 m in the spectral range 250–400 nm; 167.8 – ЕUVB/ЕUVA.
Calculated based on measurements, the value E(λ), ЕUV, ЕUVAfor distances from the lamp of 0.25 m, as well the risk group are given below.
1. Ultraviolet lamp LUF 40-1: The total value of the ЕUVat a distance of 0.25 m is 1.33 mW/m2 . The energy illumination of the ЕUVA at a distance of 0.25 m is 2459 mW/m2 . Under these conditions, the radiation from the lamps is classified as low risk (RG1).
2. UV lamp LE 15: The total value of the ЕUVat a distance of 0.25 m is 31.9 mW/m2 . The energy illumination of the ЕUVAat a distance of 0.25 m is 214.2 mW/m2 . Under these conditions, the radiation from the lamps is classified as a high risk group (RG3).
Discussions
From the given results (table 3) it can be seen that in the spectral composition of LUF 40-1 lamps there is less radiation in the UVB range and it creates a much lower erythemal irradiance. The erythemal efficiency of LE 15 lamps are 47 times higher than that of LUF 40-1. Therefore, when using such lamps in various systems of ultraviolet exposure during human irradiation, it is necessary to take into account the obtained indicators and take the necessary safety measures [37, 38].
The maximum UV exposure time is defined as tmax=30/EUV. Limits of maximum exposure to UVA: the dose should be no more than 104 J/m2 at t<1000 s; at t>1000 s – EUVA≤10 W/m2 . The maximum UVA irradiation time (in seconds) is defined as tmax=104 /EUVA. The recommended exposure time for the first action should not exceed a dose of 100 J/m2 , for the second action the dose should not exceed 250 J/m2 , and the total dose should not exceed 3000 J/m2 .
Conclusion
Based on the results of the study, the following conclusions can be drawn:
1. The photobiological safety of LUF 40-1 lamps belongs to the low-risk group RG1, and the LE 15 lamps – to the high-risk group RG3.
2. The UV code of the LUF 40-1 lamps is 40-O-4.0/3.6 and the UV code of the LE 15 lamps is 15-O-1470.0/167.8. The erythemal efficiency of LE 15 lamps are 47 times higher than that of LUF 40-1, which requires additional safety measures.
REFERENCES
[1] Lerche С.M., Philipsen Р.А. Wulf H.C. UVR: sun, lamps, pigmentation and vitamin D., Photochemical & Photobiological Sciences, 16 (2017), No. 3, 291-301 [2] Heilingloh C.S., Aufderhorst U.W., Schipper L., Dittmer U., Witzke O., Yang D., … Krawczyk A. Susceptibility of SARSCoV-2 to UV irradiation, American Journal Infection Control, 48 (2020), No. 10, 1273-1275 [3] Semenov A., Semenova K. Ultraviolet disinfection of water in recirculating aquaculture system: a case study at sturgeon caviar fish farm, Acta agriculturae Slovenica, 118 (2022), No. 3, 1-4 [4] Semenov A., Hmelnitska, Y. Ultraviolet disinfection of activated carbon from microbiological contamination, Archives of Materials Science and Engineering, 115 (2022), No. 1, 34-41. [5] Semenov A., Sakhno T., Hordieieva O., Sakhno Y. Pre-sowing treatment of vetch hairy seeds, viсia villosa using ultraviolet irradiation, Global Journal of Environmental Science and Management, 7 (2021), No. 4, 555-564 [6] Schmalwieser A.W., Siani A.M. Review on Nonoccupational Personal Solar UV Exposure Measurements, Photochemistry and Photobiology, 94 (2018), No. 5, 900-915 [7] World Health Organization. Artificial tanning devices: public health interventions to manage sunbeds, 2017. (Available 25.12.2022) http://apps.who.int/iris/bitstream/handle/10665/255695/9789241512596-eng.pdf?sequence=1 [8] Bogh M.K., Schmedes A.V., Philipsen P.A., Thieden E., Wulf H.C. Vitamin D Production after UVB Exposure Depends on Baseline Vitamin D and Total Cholesterol but not on Skin Pigmentation, Journal of Investigate Dermatology, 130 (2010), No. 2, 546-553 [9] Semenov А., Koshushko G. Device for germicidal air disinfection by ultraviolet radiation, Eastern-European Journal of Enterprise Technologies, 3 (2014), No. 10(69), 13–17 [10] Semenov A.A., Sakhno T.V. Disinfection of swimming pool water by UV irradiation and ozonation, Journal of water chemistry and technology, 43 (2021), No. 6. pp. 491-496. [11] Eysteinsdottir J.H., Olafsson J.H., Agnarsson B.A., Luethviksson B.R., Sigurgeirsson B. Psoriasis treatment: faster and long-standing results after bathing in geothermal seawater. A randomized trial of three UVB phototherapy regimens, Photodermatology, Photoimmunology & Photomedicine, 30 (2014), No. 1, 25-34 [12] Almutawa F., Thalib L., Heckman D., Sun Q., Hamzavi I., Lim H.W. Efficacy of localized phototherapy and photodynamic therapy for psoriasis: a systematic review and meta-analysis, Photodermatology, Photoimmunology & Photomedicine, 31 (2015), No. 1, 5-14 [13] Cortat B., Garcia C.C.M., Quinet A., Schuch A.P., Lima-Bessa, K.M., Menck C.F.M. The relative roles of DNA damage induced by UVA irradiation in human cells, Photochemical & Photobiological Sciences, 12 (2013), No. 8, 1483-1495 [14] Brenner M., Hearing V.J. The Protective Role of Melanin Against UV Damage in Human Skin, Photochemistry and Photobiology, 84 (2008), No. 3, 539-549 [15] Neville J.J., Palmieri T., Young A.R. Physical Determinants of nVitamin D Photosynthesis: A Review, JBMR Plus, 5 (2021), No.1, e10460 [16] McKenzie R.L., Liley J.B., Bjorn L.O. UV radiation: balancing risks and benefits, Photochemistry and Photobiology, 85 (2009), No. 1, 88-98 [17] Ikehata H. Mechanistic considerations on the wavelengthdependent variations of UVR genotoxicity and mutagenesis in skin: the discrimination of UVA-signature from UV-signature mutation, Photochemical & Photobiological Sciences, 17 (2018), 1861–1871. [18] Khan A.Q., Travers J.B., Kemp M.G. Roles of UVA Radiation and DNA Damage Responses in Melanoma Pathogenesis, Environmental Mutagen Society, 59 (2018), No. 5, 438-460 [19] Ivanov I.V., Mappes T., Schaupp P., Lappe C., Wahl S. Ultraviolet radiation oxidative stress affects eye health, Journal of Biophotonics, 11 (2018), No. 7, e201700377 [20] Modenese A., Gobba F. Cataract frequency and subtypes involved in workers assessed for their solar radiation exposure: a systematic review, Acta Ophthalmologica, 96 (2018), No. 8, 779–788 [21] Chen L.-J., Chang Y.-J., Shieh C.-F., Yu J.-H., Yang M.-C. Relationship between practices of eye protection against solar ultraviolet radiation and cataract in a rural area, PLoS One, 16 (2021), No. 7, e0255136 [22] Yan J., Ma L.-P., Liu F., Sun B., Tian M., Lu X., … Liu Q.-J. Effect of Ultraviolet B Irradiation on Melanin Content Accompanied by the Activation of p62/GATA4-Mediated Premature Senescence in HaCaT Cells, Dose Response, 20 (2022), No. 1, 1-7 [23] Kataria S., Jajoo A., Guruprasad K.N. Impact of increasing Ultraviolet-B (UV-B) radiation on photosynthetic processes, Journal of Photochemistry and Photobiology B: Biology, 137 (2014), 55-66 [24] Jansen M.A., Gaba V., Greenberg B.M. Higher plants and UV– B radiation: balancing damage? Repair and acclimation, Trends in Plant Science, 3 (1998), No. 4, 131-135. [25] Dowdy J.C., Sayre R.M. Photobiological Safety Evaluation of UV Nail Lamps, Photochemistry and Photobiology, 89 (2013), No. 4, 961-967. [26] MacFarlane D.F., Alonso C.A. Occurrence of nonmelanoma skin cancers on the hands after UV nail light exposure, Archives of Dermatology, 145 (2009), No. 4, 447-449. [27] Boniol M., Autier P., Boyle P., Gandini S. Cutaneous melanoma attributable to sunbed use: systematic review and meta– analysis, British medical journal, 345 (2012), e4757. [28] EN 60335-2-27:2013/A2:2021-11. Household and similar electrical appliances – Safety – Part 2–27: Particular requirements for appliances for skin exposure to ultraviolet and infrared radiation [29] IEC 61228:2020. Fluorescent ultraviolet lamps used for tanning-Measurement and specification method [30] Semenov A., Sakhno T., Sakhno Y. Photobiological safety of lamps and lamp systems in agriculture. Journal of Achievements in Materials and Manufacturing Engineering, 106 (2021), No. 1, 34-41 [31] Nilsen L.T.N., Hannevik M., Veierød M.B. Ultraviolet exposure from indoor tanning devices: a systematic review. British Journal of Dermatology, 174 (2016), No. 4, 730-740 [32] Sola Y., Baeza D., Gómez M., Lorente J. Ultraviolet spectral distribution and erythema–weighted irradiance from indoor tanning devices compared with solar radiation exposures. Journal of Photochemistry and Photobiology B: Biology, 161 (2016), 450-455 [33] Tierney P., Ferguson J., Ibbotson S., Dawe R., Eadie E., Moseley H. Nine out of 10 sunbeds in England emit ultraviolet radiation levels that exceed current safety limits. British Journal of Dermatology, 168 (2013), No. 3, 602-608 [34] Dybczyński W. Ocena zagrożenia spowodowanego promieniowaniem optycznym, Przegląd Elektrotechniczny, 01, 2003, 17-21 [35] EN 62471:2008. Photobiological safety of lamps and lamp systems (IEC 62471:2006, CIE S 009: 2002) [36] Pawlak A. Spektroradiometryczna metoda oceny bezpieczeństwa fotobiologicznego źródeł emitujących promieniowanie, Przegląd Elektrotechniczny, 95, 2019, nr 10, 219-224 [37] Wolska A., Latała A. Ocena ryzyka zawodowego związanego z ekspozycją na naturalne promieniowanie nadfioletowe, Bezpieczeństwo Pracy : nauka i praktyka, 07-08, 2011, nr 7/8, 12-16 [38] Wolska A., Latała A., Brański Z., Suchowicz B. Zadanie Monitorowanie ekspozycji na naturalne promieniowanie nadfioletowe u pracowników zatrudnionych na zewnętrznych stanowiskach pracy. Sprawozdanie z 3 etapu pt. Weryfikacja metodyki na podstawie badań pilotażowych. Przeprowadzenie badań i oceny ekspozycji na naturalne promieniowanie UV pracowników zatrudnionych na zewnętrznych stanowiskach pracy. Opracowanie metody oceny ryzyka zawodowego związanego z naturalnym promieniowaniem UV. CIOP-PIB, Warszawa, 2010, nr 4.5,10 pt
Authors: Anatolii Semenov, professor of the Department of Mechanical and Electrical Engineering, Poltava State Agrarian University, 1/3, Skovorody, St., Poltava, 36003, Ukraine, E-mail: asemen2015@gmail.com; Stanislav Popov, professor, head of the Department of mechanical and electrical engineering, Poltava State Agrarian University, 1/3, Skovorody, St., Poltava, 36003, Ukraine, E-mail: stanislav.popov@pdaa.edu.ua; Serhii Yakhin, professor, head of the Department of Construction and Professional Education, Poltava State Agrarian University, 1/3, Skovorody, St., Poltava, 36003, Ukraine, E-mail: sergii.iakhin@pdaa.edu.ua; Bauyrzhan Yeleussinov, Director, Branch of JSC «NCPD Orleu» Institute of professional development in Kyzylorga region, 2, Aiteke bi, St. Kyzylorda, 120700, Kazakhstan, E-mail: baur_1960@mail.ru; Tamara Sakhno, professor of the Department of Biotechnology and Chemistry, Poltava State Agrarian University, 1/3, Skovorody, St., Poltava, 36003, Ukraine, E-mail: sakhno2001@gmail.com
Source & Publisher Item Identifier: PRZEGLĄD ELEKTROTECHNICZNY, ISSN 0033-2097, R. 100 NR 2/2024. doi:10.15199/48.2024.02.31
Published by P Axelberg, Unipower AB, Sweden & M H. J. Bollen, Chalmers University of Technology, Sweden
I. INTRODUCTION
During the last decade, there has been an increasing focus on power quality (PQ). The interest and demand for quality assurance of electrical power has several fundamental causes. First of all, electrical power can be considered a product for which assured quality offers incentives to both buyer and seller. Secondly, large amounts can be saved by permanently keeping track of the quality of power from the electrical grid or network. Based on the analysis from the measurements, a cost effective maintenance or upgrading of transmission and distribution assets is possible. A third reason for the increased focus on power quality is the deregulation of the electrical power market, which is happening throughout the world. This has led to an increased awareness about power quality issues by customers who are now demanding better performance from electricity suppliers.
For example, in South American countries like Argentina, Chile and Peru and legislation forces the supplier to deliver a good power quality level, or otherwise pay a penalty if the quality is outside the set limits [1]. In Europe Electricité de France (EdF) offers customised power contracts in which quality of supply is specified and penalties paid for performance outside guarantee. The Victorian Regulator-General has recently introduced legislation in Australia to provide for compensation for damage caused by voltage variation outside set limits.
In summary there is a fundamental demand for measurements of power quality and to compare these with reference values. This requires that comparable results of measurements be achieved from different instruments. At present, this is not always the case.
The increasing need for PQ measurement has driven the requirement for standards that describe measuring methods and how the different power quality parameters are calculated and interpreted. There are already IEC standards that describe how harmonics (IEC 61000-4-7) and flicker (IEC 61000-4-15) should be calculated and presented. Unfortunately, there is still no overall standard available that covers the measurement techniques and calculations for other power quality parameters. This has led to the recent development of IEC 61000-4-30 (Testing and Measurement Techniques- Power Quality Measurement Methods) by the International Electrotechnical Commission.
The forthcoming IEC 61000-4-30 describes how a number of PQ parameters shall be calculated. Furthermore, it also classifies these parameters into two different classes depending on how the calculations are made. Manufacturers of power quality instruments can choose to develop instruments that are Normative (class A) or Indicative (class B). This standard will be an important document, used to spread the knowledge that PQ measurements for different purposes demand different performance from the instruments. It will also promote the achievement of comparable measurements from different products.
The purpose of this article is to give a short description of power quality issues, including application of fixed monitoring systems and outline the new standard IEC 61000-4-30 and its benefits to manufacturers and users of PQ analysers.
II. POWER QUALITY OVERVIEW
Power quality analysis is a well-established concept, used to evaluate the quality of electrical energy delivered to a customer. A simplified way to define the PQ concept is shown in Figure 1.
Figure 1. The power quality concept [2].
The electrical power grid or network should be designed in such a way that the supplier is always capable of guaranteeing a certain voltage quality. When loads are connected the power quality is influenced more or less depending on how the electrical network is designed and on the current profile of the loads. From this perspective, a number of basic parameters for power quality have been identified which can be measured and compared with reference values. The reference values may be absolute values or statistical values and may be obtained from standards or agreed in a bilateral contract between network generator and a customer.
For instance, a well recognised European norm is EN 50 160: Voltage characteristics of electricity supplied by public distribution systems [3], in which the parameters registered and being compared are the voltage magnitude, frequency, harmonic distortion, voltage unbalance, flicker, signaling voltages. EN 50 160 does not give any voltage characteristics for events like voltage dips, swells, transients etc. However, for the completeness a list of various events is mentioned together with indicative values. Note however that EN 50160 is not so much a requirement for the voltage quality but a description of the existing situation. The term “voltage characteristic” refers to the level not exceeded by 100% of customers during 50% of time. It is thus obvious that most locations have a voltage quality that is “better than the standard”. Measurements against the standard are only of use when this is taken into consideration.
III. DIFFERENT CATEGORIES OF POWER QUALITY MEASUREMENTS
Measurements in the power network can be split into different categories. The most common ones are demand analysis (power and energy measurements), measurements to detect disturbances, statistical measurements about the electrical grid, measurements according to standards (EN 50160 etc.) and measurements to be able to design components like transformers, capacitor bank filters etc. The various categories of measurement require different instruments.
With the increasing needs for PQ measurement, there is a growing need for standardisation. The future standard IEC 61000-4-30 will set a new benchmark for power quality measurements and will be important for both users and manufacturers of PQ instruments.
IV. CLASSIFICATION OF POWER QUALITY PARAMETERS
For the average user it is normally difficult to compare instruments. Will the instrument produce reliable results that are comparable with those from other makes? The longer the technical specification, the better, is a common approach. Unfortunately this has little to do with customer driven requirements. Here, IEC 61000-4-30 is offering a solution by classifying the power quality parameters into class A (Normative) and B (Indicative).
Instruments measuring for class B are used specifically for demand analysis and simple error search. They can be either single-phase or three phase with limited accuracy of say +/-1% per channel. Furthermore the indicative power network monitor measures only partly or not at all against given standards. However, the manufacturer of class B instrument shall define the measurement methods used.
Instruments that measure the power quality parameters according to class A are recognized as operating with the highest possible accuracy in all measuring environments/situations. The normative instrument can be used for the same kind of measurement as the indicative instrument but is especially designed to carry out normative measurements against recognised international or local standards or contracts.
Measurements made according to class A are required when verifying standards and when it comes to disputes between customer and supplier and when measurements have to be compared with those from other instruments.
What this means is that measurements that have been done with two different instruments according to class A will give the same result within the accuracy indicated in the standard. Instruments that measure according to class B only give indicative results, dependent on the method used to calculate the parameters, so that measurements taken at the same measuring point but with two different instruments could give different results. Class B instruments can be used for demand analysis, some easier disturbance trace measurements but only with measurements that do not demand an absolute accuracy. Therefore, a class A instrument will always be able to replace a class B instrument but not vice versa.
V. CHANGING DEMANDS FOR POWER QUALITY MEASUREMENTS
Considering electrical energy as a product it is self-evident that it must be quality assured. Traditionally this has been carried out by occasional short-term power quality measurements at isolated locations on the network using portable recorders. Some of these instruments produced reams of paper based data, which was hard to store and analyse. The application of modern electronics to high-speed data acquisition, signal processing, storage and analysis enables a more comprehensive and user-friendly approach from which a new trend is emerging.
IEC 61000-4-30 contains guidelines for contractual applications of power quality measurements. Whilst most parameters can be assessed over a survey period of one week, assuming no abnormal conditions occur such as severe weather, industrial action, third party interference, etc., voltage sags and swells must be assessed over a much longer period – one year is suggested. This makes sense, as dips are generally caused by faults on the network or customer’s installations – they are unpredictable, largely random and their distribution over a year can be very irregular. The implication for monitoring is profound.
A temporary survey using a portable analyser will be inadequate to monitor contractual obligations and permanent instrumentation will be required; especially since voltage dips are one of the most commonly complained about phenomena.
The following examples show how the application of permanent monitoring systems has been successfully used to tackle power quality issues.
A. Power Quality Monitoring on Wind Generators in Ireland
The number of wind generators in Ireland is rapidly increasing due to the suitability of the environment for this kind of power generation. In the southern part of Ireland, near the city of Cork, large wind generators can be seen, dotted around the countryside. However, it is well known that wind generators can cause power quality problems, particularly an increased level of flicker. In order to prevent PQ problems ESB (Eire Supply Board), one of the main suppliers of electricity in Ireland, has decided to install permanent power quality monitoring equipment in substations connected to the generators. The first batch of eighteen monitors is now working and more installations are planned. Not only the flicker, but also other important PQ parameters like sags, swells, transients are continuously monitored and measured data are regularly downloaded to the host computer via an ordinary modem or via a GSM modem for evaluation and presentation.
B. Co-operation between the local distributor and industry regarding power quality monitoring
The city of Linköping in Sweden has approximately 150,000 citizens. It is well known for its university as well as the large industry plants. The utility in Linköping was one of the first to install a permanent power quality monitoring system. It started as a quality issue with the university hospital in Linköping. Since the hospital has a lot of critical equipment, they were very concerned about the quality of their power supply. In cooperation with the utility, permanent power quality monitoring equipment was installed in the substation feeding the hospital. Today, the electrical power supplied to the hospital is fully quality assured.
In addition, the large industry plants were concerned about power quality. A mobile-phone plant and an aerospace plant have installed their own permanent power quality monitors, out-sourcing the evaluation of the measurements to the local utility on a consultant basis. This co-operation has indeed strengthened the relationship between the utility and the customer.
Success of the above projects and others has led to a mix of permanently installed power quality monitors and portable power network analysers. The permanently installed monitors continuously register the power quality at strategic locations in the electrical grid such as bulk supply points including transmission terminal stations and zone substations, as well as other important connection points to key customers – see Fig.2. Measured data is then transferred automatically, via LAN or modem, to a database where evaluation takes place against reference standards and norms and variations reported by exception.
Figure 2. Typical fixed PQ Normative monitor with GSM modem
Portable power network analysers are still used for occasional measurements at locations where no permanent monitors are installed, but these are now available with communication facilities and their measurements are integrated into the database. The control of power quality is becoming a fundamental and strategically important part of the electrical power suppliers’ quality assurance program. New business opportunities are being created based on guaranteeing a certain level of power quality. One opportunity is to be able to offer adjusted power quality to meet the customer’s particular demand and therefore get paid accordingly. This is something which has started to happen in the US and which is generating interest in the European market as well.
VI. THE FUTURE STANDARD IEC 61000-4-30
Now that the practical implications of the standard have been detailed, the following information provides an introduction to the forthcoming IEC 61000-4-30. For a more detailed description, refer to the original document [4].
“Measurement methods are described for each relevant type of parameter in terms that will make it possible to obtain reliable, repeatable and comparable results regardless of the compliant instrument being used, and regardless of its environmental conditions. This standard addresses instrumentation and measurement methods for in-site measurements, and applies to both portable and permanently installed instrumentation.” (IEC 61000-4-30; 1. Scope; p.9.)
The power quality parameters described are power frequency, magnitude of the supply voltage, flicker, supply voltage sags (dips) and swells, voltage interruptions, transient overvoltages, supply voltage unbalance, voltage and current harmonics, voltage interharmonics and mains signaling on the supply voltage and rapid voltage changes.
A. Class A and Class B
The standard describes how the power quality parameters fulfilling class A shall be calculated. For class B instruments, there are no restrictions as to how the parameters shall be calculated but the manufacturer shall specify the measurement methods used.
The following sections provide an overview of the relevant standards for class A instrumentation. To increase the readability of the text below, only 50 Hz are considered. Below discussions are valid also for a 60 Hz system.
B. Integration Times
For class A, the time integration window when recording shall be 10 cycles in a 50 Hz system. With this time integration window as a base, three measuring intervals are defined. These are 150 cycles, 10 minutes and 2 hours. The 150 cycles RMS value is calculated as the root mean square of fifteen 10 cycles RMS values. The windows shall be continuous and non-overlapping so it is easy to proof that the calculated 150 cycle value is the correct RMS value obtained. The aggregation from 150 cycles to 10-minutes is more complicated since the actual frequency will vary. When the system frequency is exactly 50 Hz, there are exactly 200 intervals. For a frequency of 49.5 Hz the 150 cycles become 3.03 seconds and there will be only 198 of them in a 10-minute interval. In most cases the number of intervals is not an integer number and the last interval is discarded in the calculation. Despite the discarded data, it remains safe to interpret URMS(10-min) as the RMS voltage over a 10-minute interval.
Each 10-minute interval must begin on an absolute 10- minute time clock, ± 20 ms. These intervals are used when calculating the voltage magnitude, harmonics and interharmonics and the voltage unbalance.
For frequency measurements a 10-seconds interval is used. There is no aggregation of frequency measurements.
C. Flagging concept
The ”flagged” concept avoids the counting of a single event more than once for different parameters, e.g. counting a single dip as both a dip and a frequency variation. When an event such as voltage dip, swell or a short interruption occurs the instrument shall only record that specific event. The other power quality parameters shall not be recorded. Instead, the interval will be flagged, meaning that it is marked to show the specific event and no other measured data. If a flag is set for a 10 cycles time window interval then the associated 150 cycles, 10 minutes and the 2 hours measurement intervals will also be flagged.
D. Frequency
The frequency shall be calculated every 10 second for class A instrument. To calculate the frequency the number of zero-crossings during 10 seconds is counted. The accuracy for class A shall be better or equal to ± 10 mHz and less than ±100 mHz for class B.
The frequency can be calculated by measuring the elapsed time between the first and the last voltage zero crossing within the 10-second interval. Let N be the number of zero-crossings within the interval and T the elapsed time, the frequency is obtained from:
.
Assuming that the value of N is correct, an accuracy of 10 mHz (2⋅10-4 of 50 Hz) requires an accuracy of 2⋅10-4 in the time measurement: 2 ms on 10 s.
E. Voltage RMS value
The voltage RMS value is calculated for every 10 cycles interval for class A instruments. Based on this 150 cycles, 10 minute and 2 hour interval values can be calculated. As shown in Section VIB the values can be interpreted as the RMS voltage over 10-cycles, 150-cycles, 10-minute, and 2-hour intervals. The accuracy for class A shall be better or equal to ± 0.10 % of nominal voltage and for class B ± 1.0 %.
F. Flicker
The flicker calculations for class A instruments shall follow the restrictions according to the norm IEC 61000- 4-15 (Flickermeter – functional and design specifications) [5].
G. Voltage dips (sags) and swells
The registration of sag/swell events shall be based on 1 cycle RMS values updated every ½ cycle for class A instruments. When this RMS value exceeds or fall below a stated triggering level, the instrument shall start recording and continue until the RMS values have returned to normal. The first instant is referred to as the start of the event, the second as the end of the event. The time between the start and the end of the event is called the duration of the event. The lowest RMS value for a voltage dip is called the retained voltage. The accuracy for class A instruments shall be within ± 0.2 % of the stated nominal voltage and ± 2.0 % for class B.
H. Unbalance
To fulfil the restrictions of class A, unbalance shall be calculated using the method of symmetrical components. From the measured phases, the three symmetrical components are calculated (positive-, negative- and the zero sequence component). The unbalance is then calculated as the ratio between the negative and the positive sequence component expressed as a percentage. Unbalance shall again be calculated over 10-cycle, 150- cycle, 10-minute and 2-hour intervals.
I. Voltage harmonics (harmonics and interharmonics)
To fulfil the requirements for class A the calculations shall be made according to IEC 61000-4-7. For a more detailed description see IEC 61000-4-7 (General guide on harmonics and interharmonics measurements and instrumentation, for power supply systems and equipment connected thereto) [6]. The basic interval for harmonic measurements is again the 10-cycle interval. A DFT (Discrete Fourier Transform) over a 10-cycle window gives a spectrum with a frequency resolution of 5 Hz. This implies that in between the harmonic frequencies (integer multiples of 50 Hz), nine additional values are available. The lowest and the highest of these are “added” to the (integer) harmonic. The remaining seven together form the “interharmonic”. Thus for the interval from 245 Hz to 305 Hz: 255 Hz is added to 250 Hz and 245 Hz to form the 5:th harmonic; 295 Hz, 300 Hz and 305 Hz form the 6:th harmonic. The remaining values: 260, 265, 270, 275, 280, 285 and 290 Hz form “interharmonic 6.5”.
J. Other power quality parameters
The above descriptions provide an introduction to the type of requirements stipulated by the forthcoming standard. For a description of other parameters, such as how transient overvoltages, rapid voltage changes, short voltage interruptions and signaling voltages shall be calculated see the original document IEC 61000-4- 30:2001.
VII. OTHER DEVELOPMENTS
Next to IEC, power quality standards are also developed within IEEE. In 1997 did both the IEEE Gold Book and IEEE Std.1346 give a method for assessing the compatibility between sensitive equipment and supply as far as voltage dips are concerned. The so-called “voltage sag co-ordination chart” enables a direct comparison between equipment voltage tolerance and the voltage dip frequency of the supply [7]. Work on interruptions and reliability has been part of an IEEE standard (recommended practice) since the publication of the first IEEE Gold Book in 1980. The most recent version (1997) even includes a chapter on stochastic prediction of voltage dips. However the IEEE never published a document on measurement of voltage quality. Project Group 1159 is working on such a document, but as yet without much concrete results. The most recent decision is to use IEC 61000-4-30 also within IEEE.
Recently a standard appeared on reliability indices (IEEE Std.1366) which recommends methods for quantifying the reliability of the supply (number and duration of long interruptions). Similar indices are currently under development in IEEE Project Group 1564. The most recent version of the working document of this group uses IEC 61000-4-30 as a basis and from here defines different levels of voltage dip indices.
The first level is formed by “event characteristics as a function of time”. The one used within IEC 61000-4-30 is the one-cycle RMS voltage updated every half cycle. The IEEE document aims at defining some additional event characteristics. From the event characteristics so-called “single-event indices” are calculated. In the case of IEC 61000-4-30 these are “duration” and “retained voltage” for voltage dips. Again some additional indices are defined.
The next level is formed by the “single-site indices”: typically the number of events per year within certain ranges of single-event indices: like the number of dips per year with a duration exceeding 100 ms and a retained voltage below 70%. The final level is the “system indices” being typically a weighted average of the single-site indices of all the monitor locations [8].
Work on power-quality indices (not just voltage dips but also harmonics, unbalance and harmonics) is also ongoing in CIGRE Working Group 36.07. This working group concentrates on the definition of appropriate system indices starting from existing standard documents. The working group also collects data to propose objectives for the indices.
VIII. CONCLUSIONS AND COMMENTS
Today, there are many types of power quality instrument on the market offering different performance according to their measurement techniques. In many cases the users are not aware of this and it is common for them to be misled, believing that results always are reliable and that measurements from different instruments always can be comparable. Unfortunately this is not always the case. Measured results from different power quality instruments are often not fully comparable against either another instrument or even against existing standards. With the increasing demand for accurate power quality supervision in the electrical network it is important that an international standard states how power quality should be measured and calculated, so that valid comparison is possible. This is particularly true for power companies and their customers entering into contractual relationships for the delivery of an assured quality of supply.
One step in this direction is the forthcoming IEC 61000-4- 30 norm (standard) that defines measuring methods and provides new ways to classify power quality instruments. The standard will lead to manufacturers of power quality instruments implementing the same measuring algorithms. Furthermore, it will be important for the end user giving them the full knowledge about instrument performance. IEC 61000-4-30 will therefore be beneficial for both manufacturers and users of power quality instruments.
IX. REFERENCES
[1] Axelberg P, Pool G, 2000, “Experiences from the deregulated electricity markets in South America”. Nordic Distribution Automation Conference. [2] Bollen M.H.J, 2000, “Understanding Power Quality Problems”. New York: IEEE press. ISBN 0-7803-4713-7,. [3] European norm EN 50 160: Voltage characteristics of electricity supplied by public distribution systems. CENELEC 1999 [4] IEC standard 61000-4-30:2001 (draft): Testing and Measurement Techniques- Power Quality Measurement Methods. [5] IEC standard 61000-4-15: Flickermeter – functional and design specifications. IEC 1999. [6] IEC standard 61000-4-7: General guide on harmonics and interharmonics measurements and instrumentation, for power supply systems and equipment connected thereto. IEC 2001. [7] Bollen M.H.J, Conrad L.E., “Voltage sag coordination for reliable plant operation”, IEEE Transactions on Industry Applications, Vol.33, No.6, pp.1459-1464. [8] IEEE, 2001, ”Voltage sag indices”. Working document for Project Group 1564, draft 2. http://grouper.ieee.org/groups/sag/.
X. BIBLIOGRAPHIES
Peter Axelberg is a senior lecturer at Högskolan i Borås, Sweden. His research activities are focused on power quality measurement techniques. He is also one of the founders of Unipower AB.
Math H. J. Bollen is professor in electric power systems at Chalmers University of Technology. Before joining Chalmers in 1996 he worked at UMIST, Manchester, UK and at Eindhoven University of Technology in The Netherlands. His research activities include various aspects of power quality. Math is co-chair of IEEE P1564 and member of CIGRE WG 36.07.
Published by 1. Jacek KUSZNIER, 2. Marcin SULKOWSKI, 3. Gabriela Druć, Bialystok University of Technology, Faculty of Electrical Engineering ORCID: 1. 0000-0001-8436-5717; 2. 0000-0002-3079-314X
Abstract. The issue of improving the energy efficiency of photovoltaic installations is very important due to the limited location options in public facilities. Therefore, this paper presents the possibilities of improving the efficiency of photovoltaic installations in such facilities using bifacial PV panels. An assessment of the energy yields and installation efficiency depending on the roofing used is made, together with an economic analysis of the effects of bifacial panels.
Streszczenie. Zagadnienie poprawy efektywności energetycznej w instalacjach fotowoltaicznych jest bardzo istotne ze względu na ograniczone możliwości lokalizacyjne w obiektach użyteczności publicznej. Dlatego też, w artykule przedstawiono możliwości poprawy wydajności instalacji fotowoltaicznych w tego typu obiektach przy zastosowaniu bifacjalnych paneli PV. Dokonano oceny uzysków energetycznych oraz wydajności instalacji w zależności od zastosowanego pokrycia dachowego wraz z analizą ekonomiczną skutków stosowania paneli bifacjalnych. (Poprawa uzysków energetycznych oraz wydajności instalacji PV przy wykorzystaniu paneli bifacjalnych w obiektach użyteczności publicznej).
Keywords: renewable energy sources, solar energy, PV panels, PV power plant. Słowa kluczowe: odnawialne źródła energii, energia słoneczna, panele fotowoltaiczne, elektrownia fotowoltaiczna.
Introduction
Public buildings such as schools, kindergartens, etc. usually have similar geometry and are most often characterized by a flat roof. The issue of improving their energy efficiency can be achieved by using photovoltaic installations placed on the roof. Increasing the generation of photovoltaic power plants in limited roof space can be achieved by using bifacial modules. The effect of improving the efficiency of PV installations can be further increased by using roof coverings with a high reflectivity (albedo). This allows the investment payback period to be shortened, which is important for the investor.
Characteristics of bifacial photovoltaic panels
Bifacial photovoltaic modules, unlike monofacial ones, are characterized by double-sided absorption of solar radiation and conversion of it into electricity.
Bifacial technology assumes the use of solar radiation not only reaching directly, but also reflected and scattered to the greatest extent possible.
The largest share in energy production comes from radiation directly falling on the photovoltaic module. However, this is not the only type of radiation that affects the efficiency of a bifacial panel. Its double-sided nature uses not only the potential of sunlight scattered in the sky, but also the radiation reflected by the ground and the module’s surroundings.
The internal structure of bifacial cells varies depending on the basic type of semiconductor [1-3]. The operation of a bifacial cell is shown in Fig. 1.
Fig.1. Energy band diagram of bifacial solar cell [1].
Changing the structure of the panels involves the introduction of additional parameters describing photovoltaic panels. In addition to the basic parameters characterizing traditional photovoltaic modules, these also include [4]:
– Bifacial Gain Energy
.
where: Isc,back – short-circuit current of the rear side of the module under STC conditions, Isc,front – short-circuit current of the front side of the module under STC conditions.
Practically, this is the value that determines the photon absorption capacity of the rear side of the bifacial module.
GE– irradiance value for measurements made using a lighting simulator [W/m2],
.
where: G0– irradiance of the radiation falling on the front side of the panel; Grear – irradiance of the radiation falling on the rear side of the panel
FFbi – filling factor of a double-sided cell
.
where: pFF – fill factor that does not take into account losses in series resistance, UOC,bi – open circuit voltage of a double-sided cell.
Radiation falling on bifacial PV panels
The production of electricity from photovoltaic sources is characterized by high variability, which results from the dependence on many environmental factors [5] and aging of PV panels [6]. Weather changes are very difficult to predict accurately [7]. It is easier to estimate the amount of energy that can be obtained over longer periods (e.g. monthly). The operating efficiency of photovoltaic power plants depends to the greatest extent on the used type of PV panels, their location, the used inverter and other system elements [8, 9].
The amount of reflected radiation depends on the type of surface under the photovoltaic installation. The key parameter determining this phenomenon is the albedo coefficient (Table 1), which determines the ratio of the light reflected to the light incident on a given plane. The higher the value of the albedo coefficient, the more reflected rays reach the rear side of the bifacial module, which consequently leads to an increase in energy production by up to 30% compared to the monofacial module. A comparison of the power achieved by different types of photovoltaic installations is shown in Fig. 2.
Fig.2. Methods of installing bifacial PV modules (a-d), where S/N – South/North, B/T – Bottom/Top, E/W – East/West; Comparison of power achieved by specific types of installations (e) [2].
Table 1. Albedo coefficient of selected surfaces
.
Assumptions of the analysed PV installation
The analysed installation will be located on a building with a flat roof measuring 50×20 m and 10 m high. The roof area is 1,000 m2 . The geometry of the facility is typical for public utility facilities such as schools, kindergartens, etc. The building is located in north-eastern part of Poland in Bialystok, installation orientation to the south – azimuth 0°, module inclination angle is 15°, power of installation PV is 50 kW, inverter with power P=50 kW (type: Huawei – SUN2000-50KTL-M3). The installation will be mounted on a supporting construction with a ballast load adapted to the specific type of modules.
The variable elements in the analysis are the type of PV modules. The following will be compared in terms of energy yields:
Analysis of energy yields and efficiency of selected variants of PV installations in public facilities
The following variants will be analysed:
• Variant 1. Photovoltaic installation with monofacial modules on a standard structure and on a roof made of graphite bituminous waterproofing,
• Variant 2. Photovoltaic installation with bifacial modules on an elevated structure and on the roof made of graphite bituminous waterproofing (albedo = 0.2),
• Variant 3. Photovoltaic installation with bifacial modules on an elevated structure and on a roof made of green bituminous waterproofing (albedo = 0.45),
• Variant 4. Photovoltaic installation with bifacial modules on an elevated structure and on a roof made of grey bituminous waterproofing (albedo = 0.75),
• Variant 5. Photovoltaic installation with bifacial modules on an elevated structure and on a roof made of white membrane or roof foil (albedo = 0.95),
In all analysed variants, the power of photovoltaic installation was P= 50 kW. The installation includes 100 modules with a power of 500 W each. The system was divided into 5 strigs of 20 photovoltaic modules, taking into account the electrical input parameters of the inverter. The considerations assume that the installation power is limited to the value for which only notification to the DSO is required, without the need to change the connection capacity for typical public utility facilities. educational.
A 3D-model was created for all design situations, after by analysing the dimensions of the building and the number of modules and strings. The photovoltaic system was divided into 10 rows of 10 panels each. The rows were spaced 4 meters gap to minimize the shading of the panels. The prepared model allowed for the analysis of energy yields and system efficiency in all indicated design variants.
Meteorological data at the workplace of the analysed PV installation are presented in Table 3.
Table 3. Meteorological data
.
The results of the simulations of individual variants allowed for a detailed comparative analysis of energy yields and the efficiency of photovoltaic installations using monofacial and bifacial modules. The irradiation values on both sides of the PV modules depending on the surface albedo value are presented in Fig. 3
Fig.3. Irradiation of both sides of the PV module depending on the surface albedo coefficient value.
Green columns show the irradiation values on the surface of monofacial modules and on the front side of bifacial modules. The columns in the remaining colors show the irradiation value on the rear surface of bifacial modules in each variants. The most advantageous of the analysed variants allows for the introduced into grid additional energy in the amount of 9,824 kWh, i.e. 19% more in relation to the use of single-sided modules. The annual energy introduced into the grid of all analysed variants and percentage values in relation to the use of single-sided modules are presented in Fig. 5 and Fig. 6.
The key value of the analysis is the PR factor (Performance Ratio) of the efficiency of the tested photovoltaic installations. It is a general indicator for comparing systems: the higher its value- the more efficient the installation.
.
Fig.4. Percentage gain of radiation reaching to modules.
Fig.5. Annual energy introduced into the grid in each variants.
Fig.6. Percentage annual gain of energy introduced into the grid
Fig.7. Performance Ratio PR factor of the efficiency of the tested photovoltaic installations.
Table 4. Costs of constructing photovoltaic installations in the analysed variants
.
Important information is also the annual distribution of electricity forecast to be introduced into the power grid. Graphs of the energy forecast to be introduced into the power grid in the following months for all analysed variants are presented in Fig. 8.
The analysis shows that in the winter period (November – February) the amount of energy produced in the installations is very similar. This is the result of a small number of sunny days and a short period of exposure to the Sun. It is also necessary to take into account the possibility of snow cover, which eliminates the possibility of producing energy from the front of the PV modules, and at the same time increases the albedo value of the ground, which increases the amount of energy generated from the rear surface of the PV module. The advantage of using bifacial modules with the simultaneous use of roof coverings with a high albedo coefficient is most visible in the period from early spring to autumn. However, the basic criterion for selecting the type of installation should be economic analysis. Due to frequent changes in the methods of settling electricity from PV installations and unstable electricity prices, the payback period method was used for analysis.
The costs of implementing the PV installation in the analysed variants are presented in Table 4, but the costs do not include the costs of roofing, as it is assumed that roofing is included in the costs of the building. The total cost of installation using bifacial modules and a dedicated supporting structure is 7.75% higher than the base version with single-sided modules.
A graph showing the payback period for the installation in all design variants is shown in Figure 9, with the energy price per 1 kWh being PLN 1.3 for the purposes of the analysis.
Fig.8. Forecasted energy introduced into the grid in the analysed variants of PV installations.
Fig.9. The payback period for the building of individual PV installation variants.
Summary
A PV installation using bifacial panels requires a supporting structure that allows the panels to be raised to a higher height. Taking into account the higher price of bifacial panels, the cost of the entire 50 kW installation is 7.5% higher than the base variant. The payback period for monofacial and bifacial installations on graphite and green felt differs by only 1 month and is approximately 22.5 – 23.5 months. In the case of a roof slope with an albedo coefficient above 0.75, the payback time for a bifacial installation is 20.5 months. These values indicate that when it is possible to use roofing with a high albedo coefficient during the construction or renovation of a public utility facility, the installation of bifacial modules on a raised structure is most justified.
The benefits in terms of increasing energy generation reach approximately 20% and are highly dependent on the ground albedo. Installations with bifacial modules allow for the greatest additional yields when located on buildings with a flat roof, which corresponds to the typical geometry of public buildings. The use of bifacial modules also increases the possibilities in terms of how to arrange the modules. For example, positioning bifacial modules vertically in the east-west direction allows for the extension of the daily generation time, which allows for better adjustment to the recipient’s demand curve. Thanks to this, it is possible to achieve a higher level of self-consumption and reduce the size of the potentially needed energy storage.
Acknowledgment -Funding: This research was funded by the Bialystok University of Technology as part of the work WZ/WEIA/3/2023.
REFERENCES
[1] Chowdhury A. A., Design, Modeling, Fabrication & Characterization of Industrial Si Solar Cells, Published by ProQuest LLC (2017). [2] Kopecek R.; Libal J., Bifacial Photovoltaics 2021: Status, Opportunities and Challenges. Energies 2021, 14, 2076. https://doi.org/10.3390/en14082076 [3] Kopecek R., Libal J., Towards large-scale deployment of bifacial photovoltaics. Nat Energy 3, 443–446 (2018). https://doi.org/10.1038/s41560-018-0178-0 [4] Kurz D., Lewandowski K., Szydłowska M., Analiza uzysku energii z fotowoltaicznych ogniw bifacjalnych. Część 1 – budowa i parametry ogniw bifacjalnych, Poznan University of Technology Academic Journals. Electrical Engineering, 2018, 215-223 [5] Kusznier J., Influence of Environmental Factors on the Intelligent Management of Photovoltaic and Wind Sections in a Hybrid Power Plant. Energies 2023, 16, 1716. https://doi.org/10.3390/en16041716 [6] Kusznier J., Wojtkowski W., “Impact of climatic conditions and solar exposure on the aging of PV panels,” 2019 15th Selected Issues of Electrical Engineering and Electronics (WZEE), Zakopane, Poland, 2019, pp. 1-6, doi: 10.1109/WZEE48932.2019.8979821. [7] Drałus G.; Mazur D.; Kusznier J.; Drałus J., Application of Artificial Intelligence Algorithms in Multilayer Perceptron and Elman Networks to Predict Photovoltaic Power Plant Generation. Energies 2023, 16, 6697. https://doi.org/10.3390/en16186697 [8] Alhmoud L., Why Does the PV Solar Power Plant Operate Ineffectively? Energies 2023, 16, 4074. https://doi.org/10.3390/en16104074 [9] Rusănescu C.O.; Rusănescu M.; Istrate I.A.; Constantin G.A.; Begea M., The Effect of Dust Deposition on the Performance of Photovoltaic Panels. Energies 2023, 16, 6794. https://doi.org/10.3390/en16196794 [10] Jinko Solar, Transparent backsheet vs dual glass – Advantages and disadvantages, PV-tech website, 2020. [11] LR5-66HIH-490~510M datasheet, en.longi-solar.com [12] LR5-66HBD-475~500M datasheet, en.longi-solar.com
Authors: Jacek Kusznier, Faculty of Electrical Engineering, Bialystok University of Technology, Bialystok, Poland, E-mail: j.kusznier@pb.edu.pl. Marcin Sulkowski, Faculty of Electrical Engineering, Bialystok University of Technology, Bialystok, Poland, E-mail: m.sullkowski@pb.edu.pl. Gabriela Druć, Faculty of Electrical Engineering, Bialystok University of Technology, Bialystok, Poland
Source & Publisher Item Identifier: PRZEGLĄD ELEKTROTECHNICZNY, ISSN 0033-2097, R. 100 NR 7/2024. doi:10.15199/48.2024.07.36
Published by 1.Nur HAMZAH, 2.Suryanto SURYANTO, 3.Muhammad ANSHAR, 4.Firman FIRMAN, 5. Muhammad Ruswandi DJALAL, 6. Muhammad Alif AL AFGAN. State Polytechnic of Ujung Pandang ORCID: 1. 0000-0002-7114-2247
Abstract. Waste is a major problem in big cities in Indonesia, one of which is Makassar City. Every year the amount of waste generated by the residents of Makassar City continues to increase, but this is not proportional to the capacity of the landfill. Therefore, researchers want to design a waste-to-energy power plant system in Makassar City or other words apply the waste-to-energy concept. The waste-to-energy concept aims to process waste into energy and reduce the volume of waste in landfills. Then the research method used is thermodynamic modelling using STEAG Ebsilon Professional version 13.02 software. From this analysis it was found that the capacity of the waste that can be burned is 742.648 tons/day, the thermal input of the incinerator is 39.011 MW, the thermal capacity of the boiler is 30.749 MW, the thermal efficiency of the waste-to-energy boiler with direct method 83.123 % and with indirect method 82.107 %, the mechanical power of the steam turbine is 10.816 MW, the heat duty of the high-pressure feed-water heater is 1,681.321 kW, the heat duty of the low-pressure feedwater heater is 1,780.234 kW, and the cooling duty of the air-cooled condenser 20.337 MW. This design has a net thermal efficiency of 24.110%, a gross plant heat rate of 12,683.130 kJ/kg, a net plant heat rate of 13,816.942 kJ/kg, an auxiliary load of 912.744 kW, a net plant power of 9.638 MWe, the specific fuel consumption 1.124 kg/kWh for each unit at the maximum load, and reducing municipal solid waste generation per year by 271,066.520 tons.
Streszczenie. Odpady stanowią poważny problem w dużych miastach Indonezji, jednym z nich jest Makassar City. Każdego roku ilość odpadów wytwarzanych przez mieszkańców Makassar City stale rośnie, jednak nie jest to proporcjonalne do pojemności składowiska. Dlatego badacze chcą zaprojektować system elektrowni przetwarzających odpady na energię w mieście Makassar, czyli innymi słowy zastosować koncepcję przetwarzania odpadów na energię. Koncepcja waste-to-energy ma na celu przetwarzanie odpadów na energię i zmniejszenie ilości odpadów trafiających na składowiska. Następnie zastosowaną metodą badawczą jest modelowanie termodynamiczne z wykorzystaniem programu STEAG Ebsilon Professional wersja 13.02. Z analizy tej wynika, że wydajność spalania odpadów możliwych do spalenia wynosi 742,648 ton/dobę, moc cieplna spalarni wynosi 39,011 MW, moc cieplna kotła wynosi 30,749 MW, sprawność cieplna spalarni -kocioł energetyczny metodą bezpośrednią 83,123 % i metodą pośrednią 82,107 %, moc mechaniczna turbiny parowej 10,816 MW, obciążenie cieplne wysokociśnieniowego podgrzewacza wody zasilającej 1681,321 kW, obciążenie cieplne niskociśnieniowego Moc podgrzewacza wody zasilającej wynosi 1780,234 kW, a wydajność chłodnicza skraplacza chłodzonego powietrzem 20,337 MW. Konstrukcja ta charakteryzuje się sprawnością cieplną netto wynoszącą 24,110%, współczynnikiem ciepła brutto instalacji wynoszącym 12 683,130 kJ/kg, współczynnikiem ciepła netto instalacji wynoszącym 13 816,942 kJ/kg, obciążeniem pomocniczym wynoszącym 912,744 kW, mocą netto instalacji wynoszącą 9,638 MWe, zużycie paliwa 1,124 kg/kWh na każdą jednostkę przy maksymalnym obciążeniu oraz ograniczenie wytwarzania odpadów komunalnych w skali roku o 271 066,520 ton. (Modelowanie termodynamiczne elektrowni przetwarzającej odpady na energię: studium przypadku w mieście Makassar w Indonezji)
Keywords: Thermodynamic-Modelling, Municipal Solid Waste, Power Plant Słowa kluczowe: Modelowanie termodynamiczne, odpady komunalne, elektrownia
Introduction
So far, boiler heat energy sources use fossil fuels, while alternative energy sources that can be considered are waste energy sources and renewable energy sources.[1]. One part of waste energy is Municipal solid waste (MSW). MSW is a term usually applied to a heterogeneous collection of wastes produced in urban areas. Generally, urban wastes can be subdivided into two major components: organic and inorganic. The characteristics and quantity of the solid waste generated in a region are a function of the standard of living in the city or country. Wastes generated in developing countries have a large proportion of organic waste, while the wastes in developed countries are more diversified with relatively larger shares of plastics and paper [2]. Almost all economic sectors generate municipal solid waste. Some factors that influence high MSW generation are population and economic growth, education, occupation, consumption patterns, and gross domestic product per capita.
With a high gross domestic product, Indonesia generates large amount of annual municipal solid waste (SW) in ASEAN countries [3]. The annual production of municipal solid waste in Indonesia reaches 31 million tons with the waste composition including food waste at 39.23%, plastic at 18.11%, paper at 12.83%, wood at 12.16%, metal at 3.19%, cloth at 2.55%, glass 2.42%, leather 1.82%, and others 7.69% [4]. Meanwhile, Makassar City’s annual solid waste production reaches 1,023,710 tons with a composition of food waste at 54.70%, wood at 11.33%, plastic at 12.20%, paper at 6.78%, textile at 1.30%, glass at 1.15%, metal 1.07%, battery 0.62%, rubber 0.42% and other 10.43% [5]. Indonesian municipal solid waste has a high moisture content, volatile matter content, as well as carbon and hydrogen content, and contains more organic matter. Moisture content is a major factor impacting calorific value. The lower heating value on the wet basis of the entire municipal solid waste sample is 8.6 MJ/kg, which is not only relatively high compared with the average calorific value, but also above the World Bank-recommended calorific value minimum for waste-to-energy applications. Thermal conversion processes including incineration, pyrolysis, and gasification for heat, bio-oil, and syngas generation are already well established and are being employed in several countries [6] . MSW in Indonesia is suitable for waste-to-energy, whether combustion (incineration) or gasification-based [7].
The concept of waste-to-energy aims to process waste into energy and reduce the volume of waste in landfills. The most commonly used technology for converting waste into energy is incineration [8]. This is because incineration technology provides a more productive way of de-creasing the amount of urban solid waste that needs to be landfilled. The incineration of municipal solid waste can minimize its mass by 70% and volume by 90%, as well as electricity and heat recovery [9]. The purpose of this research is to get a waste-to-energy power plant model that is suitable and can solve the waste problems in Makassar City.
Fuel from waste
Makassar City has a daily potential power from the waste of 24.882-33.768 MWe with an LHV variation of 7-8.6 MJ/kg and an average amount of waste of 1,023,710 tons⁄day in 2021. Makassar City municipal solid waste production data is shown in Table 1.
Table 1. Makassar City municipal solid waste production data [5].
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Waste to energy power plant description
The Makassar City waste-to-energy power plant model consists of two identical units. Each of the two waste-toenergy power plant units has a high-pressure feedwater heater, a low-pressure feedwater, a deaerator, a steam turbine, an electric generator, a boiler, and four air-cooled condenser units. The estimated incinerator capacity of this power plant is 842.7 tons per day with an estimated power that can be generated of 20,482 – 25,164 MWe. The technical data of the Makassar City waste-to-energy power plant model is shown in Table 2.
Table 1. Combustion parameters [10, 11
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Table 3. Steam and water cycle parameters [12]
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Table 2. Boiler Ratings [8],
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Table 3. Steam turbine parameters [13, 14]
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Modelling and simulation of wate to energy power plant
The modelling process was carried out by entering the technical data of the waste power plant into the model as shown in Fig. 1. The simulation process was performed to determine the performance of the model at the maximum load of each unit, which is 10.5 MWe. The performance observed in the model is the amount that can be burned, the thermal capacity of the boiler, the mechanical power of the steam turbine, the heat duty of the high-pressure feedwater heater, the heat duty of the low-pressure feedwater heater, the cooling duty of the air-cooled condenser, net thermal efficiency, net plant heat rate, auxiliary load, net plant power, and specific fuel consumption.
The equation used to calculate the net thermal efficiency of the model is as follows [15]:
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The equation used to calculate the net plant heat rate is as follows [15]
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The equation used to calculate specific fuel consumption is as follows ([15]:
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Result and discussion
After conducting a simulation of the waste power plant model as shown in Fig. 1, the researchers got the results for each unit shown in Table 6.
Table 4 Simulation results of the waste-to-energy power plant model for each unit.
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Waste to Energy Power Plant Efficiency
From the simulation results, it can be seen that the net thermal efficiency of the waste-to-energy power plant system model is 24.110%. These results are following research conducted by Mutz [16], which states that in general the thermal efficiency of waste-to-energy power plants is 20% this is in line with research conducted by Branchini [8], which states that in general the thermal efficiency of waste power plants ranges from 18% to 25% and in some cases more than 30%.
In addition, the model of the waste power plant system created by the researchers also uses a low air ratio to increase the net thermal efficiency of the waste power plant. This is in line with research conducted by Gablinge [11] which states that another benefit of using a low air ratio in a waste power plant is an increase in thermal efficiency.
Waste to Energy Boiler Efficiency
From the simulation results, it can be seen that the boiler thermal efficiency obtained is 83.123 % with the direct method and 82.107 % with the indirect method. These results are equal to the results of research conducted by Schu and Leithner [17], which state that the efficiency of the thermal waste-to-energy boiler is around 83%.
System Heat Balance
From the simulation results, it can be seen that the model of the waste-to-energy power plant system experiences the greatest heat losses in the air-cooled condenser and stack. The Sankey diagram of the model of the waste-to-energy power plant system can be seen in Fig. 2. The heat losses that occur in the air-cooled condenser are 20.337 MW or 50.237 % of the system. This happens because all the steam that has been used by the steam turbine and closed feedwater heater flows into the water-cooled condenser to change the phase from steam to water by removing the latent heat from the steam. So that the steam that has changed phase to water can flow back to the boiler. The heat losses that occur in the stack (exhaust losses) are 4.656 MW or 15.114 %. This is due to the temperature of the flue gas released into the atmosphere through the stack is high, which is 160 °C which then causes a lot of heat to be wasted from the flue gas.
Fig.1. An example of the figure inserted into the text Model of waste-to-energy power plant system using STEAG Ebsilon Professional
Fig.2. Sankey diagram from the model of waste-to-energy power plant system.
Conclusion
The thermodynamic modelling using STEAG Ebsilon Professional software version 13.02 was presented. The model of the waste-to-energy power plant for Makassar City has an incinerator daily capacity of 371.323 ton/day at the maximum load of 10.5 MWe for each unit, the thermal capacity of the waste-to-energy boiler is 30,749 MW, the thermal efficiency of the waste-to-energy boiler is 83.123 %, the thermal efficiency of the waste-to-energy boiler, the mechanical power of the steam turbine is 10.816 MW, the heat duty of the high-pressure feedwater heater is 1,681.321 kW, the heat duty of the low-pressure feedwater heater is 1,780.234 kW, and the cooling duty of the aircooled condenser 20.337 MW, the net thermal efficiency is 26.055%, the net plant heat rate is 13,816.942 kJ/kWh, the auxiliary load is 912.744 kW, a net plant power of 9.638 MWe, the specific fuel consumption is 1.124 kg/kWh with LHV 8.6 MJ/kg. This waste-to-energy power plant model is suitable to be implemented and can solve waste problems in Makassar City.
REFERENCES
[1] P. Kolasiński, Use of the renewable and waste energy sources in heat storage systems combined with ORC power plants, Przeglad Elektrotechniczny, vol. 89, (2013),no. 7, pp. 277-279, 01/01 2013. [2] H. Sudibyo, A. Majid, Y. Pradana, W. Wiratni, D. Aan, and A. Budiman, Technological Evaluation of Municipal Solid Waste Management System in Indonesia. 2017, pp. 263-269. [3] P. Lestari and Y. Trihadiningrum, The impact of improper solid waste management to plastic pollution in Indonesian coast and marine environment, Marine Pollution Bulletin, vol. 149, (2019),no. p. 110505, 2019/12/01/ 2019. [4] Ministry of Environment and Forestry Republic of Indonesia, Indonesia’s Municipal Solid Waste Production in 2021., (2022),no. 2022. [5] Department of The Environment of Makassar City, “City Municipal Solid Waste Production Report in 2021,” Department of The Environment of Makassar City, Makassar2022. [6] C. Ram, A. Kumar, and P. Rani, Municipal solid waste management: A review of waste to energy (WtE) approaches, BioResources, vol. 16, (2021),no. 2, pp. 4275-4320., 2021. [7] Z. Zongao et al., Experimental study on characteristics of municipal solid waste (MSW) in typical cites of Indonesia, Progress in Energy & Fuels, vol. 8, (2020),no. p. 13, 04/16 2020. [8] L. Branchini, Waste-to-Energy: Advanced Cycles and New Design Concepts for Efficient Power Plants. New York.: Springer International Publishing, , 2015. [9] D. Cudjoe and P. M. Acquah, Environmental impact analysis of municipal solid waste incineration in African countries, Chemosphere, vol. 265, (2021),no. p. 129186, 2021/02/01/2021. [10] C. e. a. Liu, C. Liu, T. Nishiyama, K. Kawamoto, and S. Sasaki, CCET Guidelines Se-ries on Intermediate Municipal Solid Waste Treatment Technologies Waste to Energy Incineration., IETC Technology for Environment and In-stitute for Global Environmental Strategies., (2020),no. 2020. [11] R. Strobel, M. H. Waldner, and H. Gablinger, Highly efficient combustion with low excess air in a modern energy-from-waste (EfW) plant, (in eng), Waste Manag, vol. 73, (2018),no. pp.301-306, Mar 2018. [12] J. B. Kitto and S. C. Stultz., J. B. Kitto and S. C. Stultz, Eds. Steam: Its Generation and Use, 41st ed. ed. Babcock & Wilcox Company, 2005. [13] L. Branchini, Waste-to-Energy, Advanced Cycles and New Design Concepts for Efficient Power Plants. Switzerland Springer International Publishing 2015. [14] S. AG, “Siemens Steam Turbine Portfolio,” 2019. [15] Black and Veatch, Power Plant Engineering. Boston: Springer, 1996. [16] D. Mutz, D. Hengevoss, C. Hugi, and D. Hinchliffe, Waste-toEnergy Options in Municipal Solid Waste Management – A Guide for Decision Makers in Developing and Emerging Countries. 2017. [17] R. Schu and R. Leithner, “Waste to energy–Higher efficiency with external superheating,” in Proceedings 2nd International Symposium on Energy from Biomass and Waste, Venice, Italy, 2008
Authors: Assoc Prof Nur Hamzah,, Politeknik Negeri Ujung Pandang, Jl. Perintis Kemerdekaan KM 10 Makassar Indonesia Email: hamzah_said@poliupg.ac.id
Source & Publisher Item Identifier: PRZEGLĄD ELEKTROTECHNICZNY, ISSN 0033-2097, R. 100 NR 2/2024. doi:10.15199/48.2024.02.22
Published by Dranetz Technologies, Inc., Technical Documents – White Paper
INTRODUCTION
In addition to our energy metering products, most Dranetz Power Quality products can also compute and measure common energy parameters such as W, VA, VAR, PF, Demand, Energy, and more. The ability to measure energy in addition to PQ opens the door to many more applications, including energy only applications that can include electrical consumption.
When measuring electrical consumption for billing, revenue, meter verification, or other purposes, high accuracy is often required. When the metered data is used for billing purposes, a revenue certified/grade meter may be required by code or law. When a revenue certified meter is not required, a revenue accurate meter may meet the needs of the application. Such a meter has similar accuracies as a revenue certified meter, but without the laboratory testing and the certification itself.
This White Paper summarizes the most common standards used for revenue certified energy metering and how the accuracies and capabilities of current Dranetz products compare to these standards.
STANDARDS OVERVIEW
Revenue metering standards vary around the world, but usually fall under two standards bodies: ANSI and IEC. American National Standards Institute (ANSI) standards are mostly followed in North America, with the rest of the world following the standards of the International Electrotechnical Commission (IEC). Some countries have also developed their own metering standards using variations of the ANSI and IEC standards, while others have combined aspects of both worldwide standards.
Since each link in the measurement chain is important and needs to be accounted for, there are also standards for measurement transducers. Regardless of the standards body, the overall objective of the revenue metering standards are to define the performance requirements for meters and transducers, so that compliant meters consistently, accurately, repeatedly, and reliably measure in the intended application. The applicable standards cover the ranges of measurements, temperature changes, variations in Power Factor, and other aspects of accurately metering the electricity.
ANSI STANDARDS
The important ANSI standards for metering include ANSI C12.1-2008, ANSI C12.20-2010 and also ANSI C57.13- 2008 for current transducers. The ANSI metering standards define the accuracy of the combined meter and transducers, among many other items. ANSI C12.1-2008 specifies a maximum deviation of 1% to 2% depending on the current (amps) being measured and the Power Factor. A lower Power Factor allows for a higher deviation from the reference, as does a low or high current being measured within the current measurement range.
ANSI C12.20-2010 (references ANSI C12.1) is more stringent and defines 2 accuracy “Classes”: Class 0.2 and Class 0.5. Generally speaking, as their names imply, Class 0.2 meters are allowed up to a deviation of +/- 0.2% and Class 0.5 meters are allowed up to a deviation of +/- 0.5%. These maximum deviations are at a Power Factor of 1.0, and a lower Power Factor allows for a higher deviation from the reference. Again, this is for the entire measurement system, including CT’s. Please note that this is a simplification of the standard and there are many more aspects to complying with ANSI C12.20-2010 and passing certification tests.
IEC STANDARDS
The applicable IEC standards for electricity metering equipment are IEC 62053-21 and IEC 62053-22. These standards apply to metering applications of 600V or less and also reference IEC 60044-1 for current transformers. Similar to the ANSI specifications, IEC 62053-22 is a more stringent standard with higher accuracy requirements VS. IEC 62053-21.
IEC62053-21 defines two accuracy classes of 1.0 and 2. At a Power Factor of 1.0, Class 1.0 meters are allowed up to +/- 1% error limit and Class 2 meters are allowed up a +/- 2% error limit. Lower Power Factors allow for a higher error limit.
C12.22-2010, IEC 62053-22 defines accuracy classes of 0.5s and 0.2s for the entire measurement system including CT’s. At a Power Factor of 1.0, Class 0.2s meters are allowed up to +/- 0.2% error limit and Class 0.5s meters are allowed up a +/- 0.5% error limit. Lower Power Factors allow for a higher error limit.
REVENUE ACCURATE VS. REVENUE CERTIFIED/GRADE
Both the ANSI and IEC electricity metering standards have very stringent testing requirements that go well beyond the accuracy of the meter. Even though a meter may not be revenue certified by a laboratory, it may have the accuracies of such a meter and can be used in many applications that do not require certification, but do require measurements with similar accuracies.
DRANETZ PRODUCTS & REVENUE METERING
Dranetz does not presently manufacture or sell revenue certified/grade products, but most Dranetz products meet many of the accuracy requirements of revenue certification and can be considered to be revenue accurate.
The most important core requirement in the ANSI and IEC revenue meter standards is the accuracy of the meter. Both ANSI C12.20 and IEC 62053-22 have similar accuracy requirements that depend on the “class”. Class 0.2 instruments allow for a deviation of +/- 0.2% at a Power Factor of 1.0. Class 0.5 allows for a deviation of +/- 0.5% at a Power Factor of 1.0.
The tables below show how the Dranetz portable and permanent instruments compare to the accuracy requirements of the ANSI and IEC standards.
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As noted in the tables above, CT’s and other transducers are not taken into account and can affect the accuracy of the measurements. A poorly chosen CT can negatively affect the measurements and greatly reduce the overall accuracy.
APPLICATIONS
There are many applications for revenue accurate instruments. These are usually applications where revenue certified/grade instruments are not required, but the accuracy of the measurements is still very important. Common applications are:
• Sub metering – Meter locations downstream • Load management – Manage loads in a facility • Check metering – Verify a fixed meter for accuracy • Tennent metering – Meter tenant consumption • Utility bill checking – Look for utility billing errors
Oftentimes, energy metering/monitoring is just one part of a larger power monitoring system that also includes Power Quality and other monitoring in one system. Many of the Dranetz meters referenced in the tables above also measure Power Quality, so the user has the benefit of one instrument serving multiple functions and applications.
CONCLUSION
As you can see, most of the instruments sold by Dranetz have revenue class accuracies. As a result, many customers around the world trust Dranetz products for their energy measurement needs when accuracy and dependability are required.
Published by Jacek KOZYRA1, Zbigniew ŁUKASIK1, Aldona KUŚMIŃSKA-FIJAŁKOWSKA1, Piotr TAŃSKI2, Kazimierz Pulaski University of Radom, Faculty of Transport, Electrical Engineering and Computer Science (1) Baxtom Sp. z o.o, (2) ORCID: 1. 0000-0002-6660-6713, 2. 0000-0002-7403-8760, 3. 0000-0002-9466-1031
Abstract. Poor quality of electric energy is a large problem for most of the enterprises and production plants taking actions aiming at increasing energy efficiency. Many of them have already implemented the simplest means ensuring proper quality of energy that do not require large investments. Interferences of qualitative parameters of energy will be more frequent, which is caused by ageing infrastructure and introduction of energy-efficient and power electronic devices supporting production processes. New solutions applied in the industry such as drives of variable speed and LED lighting, introduce harmonics, which results in excessive heat, reduction of capacitive reactance available in supply system and additional costs. The main goal of this publication was to present the problem of interferences caused by poor quality of electric energy in the supply systems of an industrial plant. Based on measuring data collected from an analyser mounted in a selected production plants, the causes of abnormal phenomena occurring in a supply network were determined. A solution to the problem was proposed and expected effects resulting from application of devices for compensation of generated distortions were presented.
Streszczenie. Zła jakość energii elektrycznej jest dużym problemem dla większości przedsiębiorstw i zakładów produkcyjnych podejmujących działania mające na celu zwiększenie efektywności energetycznej. Wiele z nich wdrożyło już najprostsze środki zapewniające odpowiednią jakość energii, które nie wymagają dużych inwestycji. Zakłócenia parametrów jakościowych energii będą coraz częstsze, co spowodowane jest starzeniem się infrastruktury oraz wprowadzaniem energooszczędnych i energoelektronicznych urządzeń wspomagających procesy produkcyjne. Nowe rozwiązania stosowane w przemyśle, takie jak napędy o zmiennej prędkości i oświetlenie LED, wprowadzają harmoniczne, co skutkuje nadmiernym nagrzewaniem się, zmniejszeniem reaktancji pojemnościowej dostępnej w systemie zasilania i dodatkowymi kosztami. Głównym celem niniejszej publikacji było przedstawienie problemu zakłóceń spowodowanych złą jakością energii elektrycznej w systemach zasilania zakładu przemysłowego. Na podstawie danych pomiarowych zebranych z analizatora zamontowanego w wybranych zakładach produkcyjnych określono przyczyny zjawisk nietypowych występujących w sieci zasilającej. Zaproponowano rozwiązanie problemu i przedstawiono oczekiwane efekty wynikające z zastosowania urządzeń do kompensacji generowanych zniekształceń. (Analiza eliminacji zakłóceń w systemie zasilania zakładu przemysłowego).
Keywords: Distribution company, The Quality of Electricity, Higher Harmonic, Active Harmonic Filter, AHF. Słowa kluczowe: Spółka dystrybucyjna, Jakość energii elektrycznej, Wyższe harmoniczne, Aktywny filtr harmonicznych, AHF.
Introduction
Currently supplied electric energy has become a product, characterized by many technical parameters affecting the aspects connected with reliability of power supply for selected elements of power system [1, 14]. Supply of electric energy of appropriate technical parameters results now from legal regulations and has significant impact on stability, safety and continuity of work of every industrial plant. Therefore, interest in the issues connected with quality of electric energy, methods of its measurement and improvement of its parameters has been growing for several dozen years [6].
Monitoring of the values of parameters determining the quality of electric energy has become the subject of interest of the producers, distributors and consumers [2]. Distribution companies are obliged to supply energy of specific qualitative parameters, whereas, consumers, by paying for supplied energy, feel responsible for its verification. It results from the fact that monitoring of quality of electric is significant not only due to technical and safety aspects, but it is also significant from trade point of view.
The issue of quality of electric energy is becoming increasingly important and contributes to development of technological solutions both for registering of qualitative parameters and elimination of interferences introduced to the network [3, 4, 9, 10]. Proper operation of devices requires that the values of specific features of electric energy supplied to a given receiver are within specific ranges of rated value [7, 8]. On the other hand, we have observed the growth of the number of applied receivers, which are the source of generation of distortions in the power grid, due to their non-linearity, among others, application of frequency converters [5]. At present, along with growing awareness, industrial plants invest in the solutions compensating generated distortions [16]. This fact is also caused by growing interest in the quality of energy supplied in the power grid by distribution companies because industrial plants, due to applied receiving devices, are the source of generating interferences in the network [12, 15].
The analysis presented in the publication is of research character and the main goal of this article was to present the problems connected with quality of electric energy in the supply system of the industrial plant, methods of its monitoring and improvement. Based on data collected from an analyser in a selected industrial plant, the solution to the specific problem was developed and proposed along with presenting the effects resulting from application of devices compensating generated distortions. The presented solution is an engineering example of improving current and voltage distortions, which, thanks to the reduction of generated power affecting the quality of electricity, gives measurable financial effects. The authors, thanks to the research and thorough analysis, suggest how to methodically solve the problems of deformation of power supply parameters.
The actions taken in order to improve the quality of electric energy in the energy distribution companies
From the point of view of the Distribution System Operators (DSO), reliability of energy supply is a key issue for inhabitants, enterprises and production plants. It is one of determinants of standard of living and it significantly affects economic growth of the whole country. Investment actions taken by the companies in cooperation with local governments may contribute to increasing energy safety in the communes and towns/cities. Good cooperation between local governments and energy sector allows to systematically increase indicators of reliability of energy supply and shorten power cuts. Investments in the distribution networks and cooperation while planning and expansion of power infrastructure, improving stability of power supply, give notable benefits to investors, local governments and inhabitants of the region [13, 17]. Reliability of energy supply is also the most important goal of a new model of adjustment of large energy distributors with qualitative elements, that is, a model of qualitative adjustment for distribution system operators. A model of qualitative adjustment is focused not only on increasing reliability of energy supplies to the consumers, improving safety, increasing of technical efficiency of customer service, automation of the network and improving its technical condition, but also on the aspects of the parameters of quality of energy supplied to the consumers.
The works and actions of distribution system operators aimed at monitoring and controlling of indicators of quality of electric energy have become an everyday practice, which include measurements and long-term recording [18, 19]. They are mainly forced by the complaints submitted by the consumers about the level of indicators of quality of electric energy. Collected measuring data are also of key importance for taking repairing, modernization and investment actions. The operators focus mainly on using mobile analysers, which temporarily execute measuring tasks. Operation of distribution networks is constantly monitored by the systems of constant monitoring, which are based on stationary analysers placed in key system points [20].
Another future source of data and information will be successively installed meters for remote measurement of electric energy allowing to read many parameters concerning voltage, consumed current, power and measuring harmonics and THD indicators (Total Harmonic Distortion). Additional Advanced Metering Infrastructure (AMI) will support and enable measurement and recording of indicators of quality of electric energy. In practice, above actions allow quick analysis and provide better control of receivers working in the network.
Other DSO actions aiming at improvement of quality of supplied energy taken, among others, in cooperation with the European Union based on operational programs oriented towards development of the platforms of data management from advanced measuring infrastructure, development of the system of assessment of propagation and improvement of the parameters of quality of electric energy in the distribution networks, creation of a prototype of the system supporting the process of management of WN/SN transformers based on multiparametric analysis of measuring results. These actions enable to determine optimal and significant places of measuring and monitoring of the parameters of quality of electric energy in the distribution network, estimate selected qualitative indicators and assembly of new devices and systems of on – line monitoring and assessment of quality of electric energy.
The research on the use of advanced methods of location of disturbing receivers and tools for assessment of their individual emission, including sources of harmonics and sources of voltage fluctuations are in progress. Devices and methods to improve quality for automatic reduction of the impact of disturbing receivers on the level of quality in a distribution network shall be used. The implementation of new systems is supposed to improve management of electric energy through more effective control of flow of energy, increasing reliability of energy supply and reduction of threats resulting from momentary changes of parameters of voltages and currents. The main consumers of such system will be distribution system operators and energy consumers, mainly large enterprises. Functionality of such system will be a great support while making important investment decisions aiming at improvement of quality of electric energy and reliability of energy supply.
An analysis of elimination of interferences in the supply system of the industrial plant Industrial plant supply system
A production plant, in which the research and analysis of power grid were conducted is Poultry Production and Processing Plant. The enterprise manufactures poultry products and transports them. The departments that the plant consists of:
– storage and production preparation department, – apparatus and production devices zone, – production department, – sorting department, – packing and transport department.
The poultry enterprise is supplied by 15 kV medium voltage overhead line, which includes a support structure with RUN switch. From the switch towards indoor transformer station, there is 15 kV SN cable line, which is an internal line supplying the plant. Indoor transformer station with two 630kVA transformers of 15/0,4 kV voltage ratio was built in the plant. It is 4-pole Rotoblok medium voltage switchgear along with two-section low voltage main switchgear.
In order to increase reliability of power supply, two 550 kW generators were installed in the plant, each one with an automatic transfer switching system. Power of connection of the plant to the network is 1,1 MW with installed power 1,56 MW. An important element of the production process is ensuring constant temperature during production and continuity of this process. Therefore, it is necessary to ensure high reliability of supplying the plant with electric energy. Power cuts for production devices lasting a few minutes cause losses in a technological process, and may generate big losses in mass production.
Interferences in the supply system
In 2018, new production devices with a few single-phase frequency converters controlling the production process were installed in the plant. After opening of extended part of the plant, considerable growth of temperature of a neutral conductor was observed and as a result, rebuilding and increasing diameter of neutral conductors in the department switching stations were necessary. Despite these actions, the problem of asymmetry was only partially reduced and increased temperature of neutral conductors was still observed. In order to obtain larger number of data and information about the causes of interferences in the supply system, standard measurements of the parameters of the network supplying the plant were taken.
Diagnosis of interferences started from taking readings from installed UMG 509 analysers of network parameters installed in the supplying field of the main switching station of the plant. Supply system of the plant and place of taking measurements were presented on Figure 1.
The analysers were installed for the network of asymmetrical load with current measurement in three phases. The analysers showed even loads of specific phases and substantial flow of current in a neutral conductor. Based on the measurements, it was found that supply network is characterized by the presence of high rates of total harmonic voltage and current distortion, which amount to for current: L1–27%, L2–28,5%, L3–28% and N–2231,7% and for voltages: L1–4,8%, L2– 4,9%, L3–4,8% and N–18,5%. Measurement of power in specific phases for considered electric switchgears was, on average 108,5 kW. The results of all measurements were presented in the Tables 1÷3.
Table 1. The results of measurements of current, power, THDU and THDI in the supply system
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Table 2. The results of measurements of current harmonics in the supply system
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Table 3. The results of measurements of voltage harmonics in the supply system
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Measuring equipment registered 9 voltage harmonics and 1, 2, 3, 5, 7 and 9 current harmonics. The highest values of current harmonics for the phases were observed in the event of basic harmonics and 3 harmonics in a neutral conductor. It must be said that 3 harmonics for specific phases also have high values (on average 127 A).
Measurements and analysis of quality of energy using UMG 509 analyser were conducted in all selected department switchgears of the plant. An analysis of conducted research and recording of measurements showed that the source of interferences are started and put into operation production devices supplied from department switchgears R1, R2, R3, R4, R5, R6, R7, R8, R9. Every switchgear supplies twelve devices with 2,2 kW single-phase frequency converter. The switchgears were adapted to supply asymmetrical circuits as four-wire supply system with a neutral conductor. Occurrence of third harmonics and their multiples was considered for asymmetrical circuits. In the examined switchgears according to the PN-EN 610000-3- 12 standard, Rsce > 350 and permissible value of current of third harmonics is 41% of rated current.
It was determined that in the event of asymmetrical load, current of third harmonics resulting from summing up currents of third harmonics coming from three phases occurs in a neutral conductor. In particularly bad situation, algebraic summing of these three phase currents occurs, which causes flow in neutral conductor current of the value of 123% of rated current. This value is many times greater than the permissible 41% of the rated current, which is defined as in the PN-EN 610000-3-12 standard. [21]
The measurements show occurrence of higher harmonics, which considerably complicates operation of the network and electric devices and causes increased power losses and problems with calculating voltage drops. Applicable regulations limit permissible values of both currents and voltages of higher harmonics in all electrical circuits, both low- and high-voltage ones.
Elimination of interferences of the supply system
In order to eliminate interferences in the power grid of the plant, taking specificity and need of reliability of power supply into account, it was accepted that best method of elimination of interferences will be assembly of active filters. Active filters near the source of generation of interferences will be mounted in every switchgear supplying production devices. Sinexcel Active Harmonic Filters were applied to reduce higher harmonics. Filters of active harmonics reduce harmonics caused by non-linear load to the power grids [10]. It is usually installed in parallel to pollution loads. Active filter analyses harmonics of the mains electricity consumed by the loads and generates compensatory current as an opposite phase angle, neutralizing current harmonics. A set of modular Sinexcel Active Harmonic Filters is suitable for all types of applications, providing balancing of load with filtering of harmonics and stepless compensation of reactive power for leading and lagging loads. Figure 2 presents the filter applied to eliminate interferences in the modernized network.
As shown in Figure 2, Sinexcel AHF detects the load current in real time via external current transformer and extracts the harmonic content of the load current. After analyzing the data, the controller the AHF drives the internal IGBT with the PWM signals and causes the inverter to produce the reverse current of the same harmonic magnitude of the load, which is injected to the power grid to compensate for harmonic current [11].
In the production plant, interferences in the supply network have the form of:
– presence of 1st-9th order harmonics, – high value of total harmonic current distortion, – high value of total harmonic voltage distortion, – increased power consumption caused by harmonics and voltage and current distortion, – increased current flow caused by harmonics and current distortion
n order to eliminate interferences in the network, active filters of current and voltage harmonics are recommended. In the first stage of modifications of the network, 1 filter was installed. Then, due to the necessity of reduction of higher harmonics, the number of installed filters was increased to 8. The places of installation of AHF filters were presented on Figure 3.
The results of measurements for 1 filter mounted next to department switchgear R1 were presented in Tables 4÷6.
Table 4. The results of measurements of current, power, THDU and THDI in the supply system
.
Table 5. The results of measurements of current harmonics in the supply system
.
Fig.1. Supply diagram of the plant along with a place where measurements were taken using UMG 509 analyser
Fig.2. Applied harmonic filters AHF [11]
Fig.3. Supply diagram of the plant along with a place of installation of AHF filters
Whereas, the measurements with 8 filters mounted in department switchgears R1÷R8 were presented in the Tab. 7÷9.
Table 7. The results of measurements of current, power, THDU and THDI in the supply system
.
Table 8. The results of measurements of current harmonics in the supply system
.
Table 9. The results of measurements of voltage harmonics in the supply system
.
Based on obtained results of the measurements, Figure 4 presents the results of the measurements of current. Measuring data before installation of the filters and after installation of 1 filter and 8 filters were compared.
As a result of taken actions, power consumption in all phases noticeably decreased. In L1 and L2 phases, installation of additional 7 filters reduced current by additional 4%, whereas, no visible differences were observed in L3 phase. The greatest effect caused by installation of a set of 8 filters has been observed in the event of a neutral conductor – from 356,6 A to 12,6 A.
Fig.4. The measurements of currents without installation of the filter and after installation of 1 filter and 8 filter
The comparison of the results of power consumption in the plant without installation of the filters and after installation of one filter and set of 8 filters was presented on Figure 5.
Fig.5. The measurements of power consumption without installation of the filter and after installation of 1 filter and 8 filter
Fig.6. The measurements of total harmonic voltage distortion (THDU) without installation of the filter and after installation of 1filter and 8 filters
The results of the measurements of power consumption clearly show reduction of power generated for considered electric switchgears of the plant by 6,6 kW. Within a year, it enabled to save money and gave financial profit for the plant amounting to PLN 35000. Whereas, Figure 6 presents the results of the measurements of total harmonic voltage distortion (THDU).
Installation of one filter reduced THDU in phase N by 1,5%. In the event of L1-L3 phases, reliable changes have not been observed. Whereas, a set of the filters almost totally reduced parameters in all phases. Whereas, Figure 7 presents the results of the measurements of total harmonic voltage distortion.
Fig.7. The measurements of total harmonic current distortion (THDI) without installation of the filter and after installation of 1filter and 8 filters
Installation of one filter reduced THDI in L1-L3 phases by about 3 % and after installation of 8 filters, by on average 4%. In the even of phase N, 1 filter reduced THDI by 20%, and additional 8 filters practically completely minimized current distortions.
Fig.8. Measurement of current harmonics without installation of the filters
Fig.9. Measurement of voltage harmonics without installation of the filters
While assessing proposed solution, we must also analyse the impact of mounted AHF filters on reduction of higher harmonics. Figure 8 and 9 present the results of the measurements of current and voltage harmonics before assembly of the filters in the supply system of switchgears. Particular attention should be paid to high values of 3rd and 5th order harmonics, both for currents and voltages.
Installation of the first filter slightly reduced the values of 3rd order harmonics, by 5 and 11 A. A list of the results of measurements of current harmonics after installation of 1 filter was presented on Figure 10, whereas, Figure 11 presents the results of the measurements of voltage harmonics after installation of the first filter. No considerable changes have been observed on presented figure, which shows the necessity to still use additional filters in the supply system.
Fig.10. Measurement of current harmonics after installation of 1 AHF filter
Fig.11. Measurement of voltage harmonics after installation of 1 AHF filter
In order to achieve set goal of improvement of quality of electric energy in the network supplying the production plant, the number of installed filters was increased to 8. Figure 12 presents the results of measurements of current harmonics after installation of 8 active filters in the plant supply system. In the event of basic harmonics, the value of current was reduced by nearly 62 A in L1-L3 phases and the phase N was marginalized. Tertiary harmonics were reduced by over 90%.
Fig.12. Measurement of current harmonics after installation of 8 filters
Fig.13. Measurement of voltage harmonics after installation of 8 filters
The results of the measurements of voltage harmonics after installation of 8 filters in the plant were presented on Figure 13. Value for 3rd and 5th order harmonics was considerably improved.
Finally, based on 8 mounted filters, each one for single switchgear directly supplying the production devices, there was a notable impact on reduction of higher voltage and current harmonics. This reduction was a decisive factor of reduction of current in a neutral conductor and its overheating.
An important aspect of the presented modernization is the plant’s savings resulting from the decrease in power consumed as a result of installing filters. The recorded total power decrease of 6.6 kW, which, with the continuous operation of the plant resulting from the specificity of the production, results in the calculation of 6.6 x 24 houers = 158.4 kWh/day, i.e. 57,816 kWh/year in total. With the electricity rate applicable at the time of installation, PLN 0.6 /1kWh gives us PLN 34689.6 per year. Currently, due to the change in electricity purchase prices to PLN 1-1.2/1kWh, the savings reach even PLN 70,000 per year. The cost of purchasing such a device AHF at the time of implementation was PLN 23,000, i.e. 8 x PLN 23,000 = PLN 195,000. The gain from modernization is obvious and indisputable.
Conclusions
In recent years, intense changes occurred in technologies used by business entities. Obsolete devices were replaced with new ones and sometimes whole process lines equipped with electronic and power electronic devices were developed. New devices, although they consume less energy, need to be supplied in appropriate parameters due to too low or too high supply voltage. Therefore, Energy Distribution Operators are required to supply the consumers uninterruptedly and supply energy of appropriate qualitative parameters. More emphasis is put on duration of power cuts, but also on the value of supply voltage, which is specified by legal regulations. Significant and desired issue is the possibility of an analysis of voltage and current inside the network for the purpose of an analysis of archived measurements of current and voltage, which can be used to determine potential load capacity of an existing network, or to make a decision about modernization. On the other hand, the consumers are more and more aware of legal aspects within the scope of quality of electric energy that should be supplied, and access to various types of devices for archiving and analysis of voltage and current in the consumer system.
An analysis conducted based on the measurements showed occurrence of higher harmonics which considerably complicates operation of the networks and electric devices and causes increased power losses and problems with calculating voltage drops.
In order to eliminate interferences in the power grid of the production plant, considering specificity and need of reliability of power supply, it was assumed that the best method of elimination of interferences would be assembly of active filters AHF next to each switchgear supplying the production devices, that is, in the source of interferences.
The basis of modernization of considered industrial network in the production plant was assembly of harmonic filters to eliminate interferences. The effects included:
– Expected effect of current reduction in a neutral conductor by installing a set of 8 AHF filters, which decreased from 356,6 A to 12,6 A during current measurement for a neutral conductor,
– Reduction of total harmonic current distortion (THDI) after installation of the filters by about 4%,
– Decrease by 6,6 kW of power generated by the plant, which would give financial profit amounting to PLN 35000 within one year,
– Total reduction of harmonic voltage distortion (THDU) in all phases,
– Reduction of current distortions (THDI) in L1-L3 phases by about 3 % for installation of 1 filter and reduction by on average 4% after installation of 8 filters,
– In the event of a neutral conductor, one filter allowed to reduce THDI by 20% and additional 8 filters allowed to minimize current distortions in this conductor,
– Reduction by 90% of value of current of 3rd order harmonics and marginalization of other harmonics of higher orders.
The innovation presented in the presented research material was understood as the use of technical solutions in order to eliminate the problem of deformation of the power supply parameters in a simple and economical way by using a device to compensate for the generated deformations. This is a very well presented technical problem that has been solved by a simple technical application with a measurable financial effect.
The authors of this article think that constant development and modernization of industrial infrastructure will force the Distribution System Operators and technical services of the enterprises to constantly monitor the parameters of quality of electric energy. Development of smart networks and supply systems will be necessary. It will result in increased number of measuring points that will allow to follow the dynamics of changes of voltage and load currents. Archived data will also be significant, allowing to conduct an analysis of the parameters of electric energy in various supply points, in order to determine connections of additional sources of energy or making a decision about investment works connected with expansion of a network.
REFERENCES
[1] Dugan R. C,. McGranaghan M. F., Santoso S., Beaty H.W., Electrical Power Systems Quality, McGraw-Hill Education, Third Edition, 2012 [2] Povh D., Pregizer K., Weinhold M., Zurowski R., Improvement of supply quality in distribution systems, 14th International Conference and Exhibition on Electricity Distribution. Part 1. Contributions (IEE Conf. Publ. No. 438), 1997, 27/1-27/6, ISBN: 0-85296-674-1, doi: 10.1049/cp:19970494 [3] Mangold M., Weinhold R., Zurowski T., Voss, L., Power Conditioning Equipment for Improvement of Power Quality in Distribution Systems, cgti.org.br [4] Lei X., Retzmann D., Weinhold M., Improvement of power quality with advanced power electronic equipment, DRPT2000. International Conference on Electric Utility Deregulation and Restructuring and Power Technologies. Proceedings (Cat. No.00EX382), 2000, 437-442, doi: 10.1109/DRPT.2000.855704 [5] Jensen M.M., Hansen H., Triplen harmonics in the low voltage network, Nordac conference, Stockholm, 8-9 September 2014 [6] Ceaki O., Seritan G., Vatu R., Mancasi M., Analysis of power quality improvement in smart grids, 10th International Symposium on Advanced Topics in Electrical Engineering (ATEE), 2017, 797-801, doi: 10.1109/ATEE.2017.7905104 [7] Ye G., Power quality in distribution networks: estimation and measurement of harmonic distortion and voltage dips. ISBN: 978-90-386-4405-9, 2017, Printed by Ipskamp Drukkers, Enschede [8] Łukasik Z., Kozyra J., Kuśmińska-Fijałkowska A., Górecki R., Supplying electricity to service and business complexes, 2018 ELEKTRO, 2018, 1-6, doi: 10.1109/ELEKTRO.2018.8398295 [9] Wang B., Xu W., Pan Z., Voltage sag state estimation for power distribution systems, IEEE Transactions on Power Systems, 20(2), 2005, 806-812, doi: 10.1109/TPWRS.2005.846174 [10] Bollen M. H. J., Understanding Power Quality Problems Voltage Sags and Interruptions. IEEE Press, 2001, New York [11] Sinexcel AHF One-Set and Multi-Set System (25~600A), User’s Manual BOM, No.: A81150060 [12] Bhattacharyya S., Power quality requirements and responsibilities at the point of connection, Ph.D. dissertation, Eindhoven Univertsity of Technology, 2011 [13] Vitaliy K., Nikolay T., Yevheniia K., Evaluating the Effect of Electric Power Quality upon the Efficiency of Electric Power Consumption, 2019 IEEE 2nd Ukraine Conference on Electrical and Computer Engineering (UKRCON), 2019, 556-561, doi: 10.1109/UKRCON.2019.8879841 [14] Sankaran C., Power quality. CRC press, 2017 [15] Gosbell V.J., Perera B.S.P., Herath H.M.S.C., New framework for utility power quality (PQ) data analysis. Proceedings AUPEC’01, Perth, 2001, 577–582 [16] Saxena D., Bhaumik S., Singh S., Identification of Multiple Harmonic Sources in Power System Using Optimally Placed Voltage Measurement Devices, IEEE Transactions on Industrial Electronics, 2014, 61(5), 2483-2492, doi: 10.1109/TIE.2013.2270218 [17] Łukasik Z., Kozyra J., Kuśmińska-Fijałkowska A., System of guaranteed power supply for the purposes of automated laser cutter in technologies of industrial cutting materials, 2020 ELEKTRO, 2020, 1-6, doi: 10.1109/ELEKTRO49696.2020.9130189 [18] Broshi A., Monitoring power quality beyond EN 50160 and IEC 61000-4-30, 9th International Conference on Electrical Power Quality and Utilisation, 2007, 1-6, doi: 10.1109/EPQU.2007.4424114 [19] Dolara A.; Leva S., Power Quality and Harmonic Analysis of End User Devices. Energies, 2012, 5(12), 5453-5466, doi: https://doi.org/10.3390/en5125453 [20] Hossain E., Tür M. R., Padmanaban S., Ay S., Khan I., Analysis and Mitigation of Power Quality Issues in Distributed Generation Systems Using Custom Power Devices, IEEE Access, 2018, 6, 16816-16833, doi: 10.1109/ACCESS.2018.2814981 [21] PN-EN 61000-3-12: 2012 Electromagnetic Compatibility (EMC) – Part 3-12: Limits for Harmonic Currents Produced by Equipment Connected to Public Low-Voltage Systems with Input Current 16A < and = 75A Per Phase
Authors: dr hab. inż. Jacek Kozyra, prof. URad., Uniwersytet Radomski im. Kazimierza Pułaskiego, Wydział Transportu, Elektrotechniki i Informatyki, ul. Malczewskiego 29, 26-600 Radom, Email: j.kozyra@uthrad.pl.; prof. dr hab. inż. Zbigniew Łukasik, Uniwersytet Radomski im. Kazimierza Pułaskiego Wydział Transportu, Elektrotechniki i Informatyki, ul. Malczewskiego 29, 26-600 Radom, E-mail: z.lukasik@uthrad.pl; dr hab. inż. Aldona KuśmińskaFijałkowska, prof. URad., Uniwersytet Radomski im. Kazimierza Pułaskiego Wydział Transportu, Elektrotechniki i Informatyki, ul. Malczewskiego 29, 26-600 Radom, E-mail: a.kusmińska@uthrad.pl; mgr inż. Piotr Tański, Baxtom Sp. z o.o., 06-500 Mława, ul. Browarna 4, Email: p.tanski@baxtom.com.
Source & Publisher Item Identifier: PRZEGLĄD ELEKTROTECHNICZNY, ISSN 0033-2097, R. 100 NR 4/2024
Published by Dawid ZIĘBA1, Jacek RĄBKOWSKI2, Medcom Company (1), Warsaw University of Technology, Institute of Control and Industrial Electronics (2) ORCID: 1. 0000-0003-3789-6851; 2. 0000-0001-8857-3505
Abstract. The article presents a discussion on the limitations of the flexible Rogowski current probes in the measurements of switching processes in ultra-fast SiC MOSFET power modules. The probes feature limited bandwidth of up to 50 MHz and might be susceptible to electromagnetic interferences caused by the rapid-switching processes. The obtained waveforms of the SiC MOSFET power module are compared to the waveforms captured using calibrated coaxial current shunt resistor that features a 2 GHz bandwidth.
Streszczenie. W artykule podjęto dyskusję nad ograniczeniami sond prądowych w formie elastycznych cewek Rogowskiego przy pomiarach szybkich procesów łączeniowych modułów tranzystorowych SiC MOSFET. Sondy te charakteryzują się ograniczonym pasmem przenoszenia do 50 MHz i mogą być podatne na zakłócenia elektromagnetyczne jakie towarzyszą szybkim procesom łączeniowym. Wykonano testy dwupulsowe i przebiegi uzyskane przy pomocy wybranych trzech cewek Rogowskiego porównano z przebiegami zarejestrowanymi przy użyciu skalibrowanego koaksjalnego bocznika rezystancyjnego o paśmie przenoszenia 2 GHz. (Elastyczne cewki Rogowskiego w pomiarach szybko przełączających modułów tranzystorowych SiC MOSFET – ograniczenia i wyzwania ).
Keywords: SiC MOSFET, fast-switching, power modules, Rogowski coils. Słowa kluczowe: SiC MOSFET, szybko przełączające, moduły tranzystorowe, cewki Rogowskiego
Introduction
Recently, the status of Silicon Carbide (SiC) semiconductors in the power electronic industry came to the point where these devices have become a standard choice for innovative, high-efficiency solutions. In the automotive sector, responsible for the majority of the SiC market growth, main players already use SiC components in their long-range electric vehicles (EVs) [1-5]. Apart from the automotive sector, rolling-stock companies also apply SiC semiconductors as a standard solution for high-efficiency converters dedicated to trains, trams, and other public transport vehicles [6-9]. According to market research, the global market for SiC power devices is expected to grow by 41,4% year-on-year in 2023 [10]. That is caused mainly by the chip-makers joining collaborative relationships with the transportation and renewable energy sectors. These trends are expected to remain the same for at least the next five years. Even though SiC-based devices are most often more expensive compared to classic silicon (Si) based solutions, the gains from higher efficiency, smaller and lighter power electronics converters, and potentially more extended range on the same battery in the case of EVs bring SiC components to the top choice position and definitely will affect the semiconductors market share in the following years. However, as the switching speed of new transistors increase, new challenges appear. One of the main issues important in the design process of power converters is proper measurements of the transistor voltages and currents to find switching energies. Especially current measurement technologies are the main problem due to bandwidth limitations. In the case of power modules discussed in this paper, the most common current probes are Rogowski coils, current transformers, and current shunts. Among these three, the flexible Rogowski coils are the ones that are the most versatile. However, speaking of flexible Rogowski coils, they feature relatively low bandwidth, recently of up to 50 MHz [11]. Taking into consideration that SiC MOSFETs can switch hundreds of amps in tens of nanoseconds, the question arises whether these current probes are suitable for new power modules. In a Tektronix application note [12], one can read that Rogowski coil current probes are unsuitable for SiC MOSFET power modules current measurements.
However, only a coil with a bandwidth limited to 30 MHz has been tested. On the other hand, a manufacturer of a 50 MHz Rogowski coil current probe selected in this paper clearly states that it has been optimized for fast-switching devices such as SiC [11].
In this article, a comparison of the performance of selected flexible Rogowski coil current probes available on the market, featuring bandwidth in the range of 23-50 MHz with the reference of a 2 GHz bandwidth coaxial current shunt resistor, is presented. A rapid-switching SiC MOSFET module (Microchip MSCSM120AM042CT6LIAG) has been selected for measurements according to a standard double pulse test (DPT) technique [13]. The experimental results are presented and discussed.
New challenges related to fast switching capabilities of SiC semiconductors – transistor current measurements
As mentioned above, SiC MOSFET power modules have become common building blocks for high-power new generation power electronics converters. As their switching behavior is far different compared to the one well known from their silicon counterparts, Si IGBTs, which exhibit much slower switching, additional phenomena related to the parasitic parameters of the semiconductors and the whole power loops must be considered [14]. Otherwise, the obtained results of performed measurements might be highly erroneous [15]. As an effect, the designed power electronics converters might be far from optimal. Apart from that, in order to be able to perform the measurements of new-generation rapid-switching SiC MOSFET modules correctly, special care has to be taken considering not only the power loop but also the measuring rig itself.
Nowadays, SiC MOSFET transistors in power modules are capable of switching with drain-source voltage slopes exceeding 50 kV/μs while switching nominal currents of hundreds of amps in tens of nanoseconds. Moreover, the next generations of SiC semiconductors are expected to gain even faster switching capabilities. That fast switching processes are accompanied by significant radiation of electromagnetic interferences (EMI) that might affect the output signals of the measuring voltage and current probes.
For drain-source voltage measurements, differential, high-bandwidth, and high common mode rejection ratio (CMRR) voltage probes are strongly advised to be used in order to minimize the distortions of the waveforms. Considering the current measurements, the transistor current can be measured either using a Rogowski coil, a current transformer, or a coaxial current shunt resistor (CCSR) [16]. The best option seems to be CCSRs, as they feature a bandwidth as high as 2 GHz [17]. However, they are challenging to apply in real industrial applications, as in most cases, they need mechanically sophisticated power loops that are often far from optimal considering the busbar design connecting the power module with the DC-link capacitors, with minimized parasitic inductance. The same observations are valid in the case of current transformers (CTs). Present-day current transformers achieve measurement bandwidths of up to 250 MHz [18]. Nevertheless, this comes with a trade-off, as the magnetic core saturation limitation necessitates a relatively large cross-sectional area, resulting in relatively huge dimensions. It is important to notice that the usage of both CCSR or CTs, in most cases, substantially increases the overall parasitic inductance of the power loop. In the case of a CCSR, that is caused by the current leads that are not fully magnetically coupled, even if minimized in length. Considering the CT case, the increase of parasitic inductance in the power loop might be so high due to the parts of busbars that are not magnetically coupled that it might eliminate the reasonableness of their use. Moreover, changes in the parasitic inductance of the power loop influence the amount of energy stored in the distributed parasitic inductance over the whole power loop and its resonance frequency, which directly impacts the switching waveforms.
An alternative solution is a widely-used current sensor: the Rogowski coil (RC), which relies on Faraday’s induction law [19,20]. Employing a helix coil, it directly captures the derivative of the current, subsequently reconstructing the original current signal through either a passive or active integrating circuit (figure 1), as described by equation 1.
.
where: vROG – the voltage at the Rogwoski coil terminals, μ0 – vacuum permeability N – number of turns, A – the winding area, r – radius between the center of the conductor and the winding, M – the mutual inductance of the Rogowski coil.
That type of current probe is a common way of measuring a power module transistor current during double-pulse tests. However, regarding flexible Rogowski coil current probes (RCCP) that are very practical in fast prototyping and can easily be used in tests of power modules in various packages, unfortunately, they exhibit considerable limitations. Recently, they feature a limited bandwidth of up to 50 MHz but more common flexible RCCPs on the market feature even lower bandwidth in the 20-30 MHz range.
A comparison of the performance of RCCPs to the 2 GHz bandwidth calibrated CCSR
Three commonly available on the market Rogowski coil current probes have been selected for test purposes. CWTMini50HF/15, CWTUM30, and CWTMiniHF30 models (all manufactured by PEM company) with bandwidths of 50 MHz, 30 MHz, and 23 MHz, respectively, have been tested. A calibrated CCSR Powertek SDN-414-10 with 2 GHz bandwidth has been used as a reference current sensor. To fully use the rapid-switching capabilities of new generation SiC MOSFET power modules, a sophisticated double-pulse test-bench based on the Advanced Conversion 700D590 power ring film capacitor and dedicated busbars has been prepared.
The Microsemi MSCSM120AM042CT6-LIAG 1200 V, 495 A SiC MOSFET module was connected to laminated busbars designed to allow a CCSR insertion into the power loop. The CCSR underwent mechanical modifications in order to minimize the additional parasitic inductance added into the power loop. As a result, a total parasitic inductance was limited to 24 nH even with the CCSR installed. The SiC MOSFET power module under test with the CCSR and 50 MHz bandwidth Rogowski coil installed in the power loop has been presented in figure 2.
Fig.1. The Rogowski coil current probe circuit diagram
Fig.2. The Microchip MSCSM120AM042CT6LIAG SiC MOSFET power module connected to the double-pulse test test-bench, used for comparison of the performance of selected Rogowski coil current probes
In addition, the custom-made air core 50 μH inductor has been used as a load inductance. The MOSFET gate has been driven by a modified high-performance low output impedance gate driver from the Medcom company, providing voltages of +20 V/-5 V, as recommended by the manufacturer of the tested SiC power module. In order to achieve the fastest switching possible, no additional external gate resistor was included in the gate loop (RG = 0 Ω). The gate driver output and the MOSFET under test gate and source connection terminals were connected using a short high-bandwidth coaxial cable to minimize parasitic inductance in the gate loop. The drain-source voltage waveforms of the SiC MOSFET transistor under test were obtained using Tektronix THDP0200 differential voltage probe. A Tektronix MSO46 series oscilloscope has been used to capture the waveforms. Output signals of voltage and current probes were precisely time-aligned using a method described in [14]. Considering the intentionally imperfect (non-central) placement of the Rogowski coil relative to the primary conductor in this research work, an accuracy of ± 2% is expected, according to the manufacturer. An operating point with a power supply voltage of 600 V has been chosen, as the DUT is a 1,2 kV class device. The DPT tests have been performed with all three selected Rogowski coils one after another, as it was impossible to fit all three at the same time on optimized low parasitic inductance busbars.
Selected turn-on and turn-off waveforms recorded during the switching of 400 A source current are presented in figures 3-5. They show a comparison of current waveforms obtained with RCCPs and reference CCSR. It shows that after the time alignment, the main slopes for both turn-on and turn-off processes are quite similar in shape compared to the reference waveform of the coaxial shunt resistor. However, the shapes of the current waveforms obtained by the RCCP are distorted, especially in the post-switching oscillation phase. The lower the bandwidth of the RCCP is, the more the particular waveform is distorted. The RCCP featuring 50 MHz bandwidth provided the waveform with significantly reduced amplitude of the oscillations (76% of the amplitude in the CCSR waveform), even though the oscillations frequency is 17,15 MHz, which is far from the claimed 50 MHz bandwidth (-3 dB). The shape, on the other hand, is reproduced reliably without significant distortions caused by EMI. The 30 MHz bandwidth RCCP performed similarly to the 50 MHz RCCP, but significantly greater distortions in the waveform can be observed. That means that 30 MHz RCCP is more susceptible to EMI. The measured current waveforms might be far from reality, suggesting huge oscillations in the power module itself, unequal current sharing between the chips inside the module, or poor gate-source voltage control in the power module under test. In the case of 23 MHz RCCP (Fig. 5), the current shape is significantly distorted and out of phase. That shows substantial susceptibility to EMI radiated during rapid switching processes. This RCCP is definitely not suitable for measurements of fast-switching SiC MOSFET power modules, as obtained waveforms are not reliable. In the authors’ opinion, this is caused mainly due to the susceptibility of the selected RCCP to the EMI occurring during fast switching processes.
All in all, unfortunately, all the selected RCCPs did not fully meet the criteria of reliable, current waveform reproduction, suggesting that further research and development of higher bandwidth flexible RCCPs that are immune to the EMI is needed.
Fig.3. Selected turn-on and turn-off waveforms of the drain-source voltage vDS and the source current of the SiC MOSFET under test measured with the CWTMini50HF/15 Rogowski coil current probe with 50 MHz bandwidth (iS_COIL_50_MHz) and current shunt resistor (iS_SHUNT)
Fig.4. Selected turn-on and turn-off waveforms of the drain-source voltage vDS and the source current of the SiC MOSFET under test measured with the CWTUM30 Rogowski coil current probe with 30 MHz bandwidth (iS_COIL_30_MHz) and current shunt resistor (iS_SHUNT)
Fig.5. Selected turn-on and turn-off waveforms of the drain-source voltage vDS and the source current of the SiC MOSFET under test measured with the CWTMiniHF30 Rogowski coil current probe with 23 MHz bandwidth (iS_COIL_23_MHz) and current shunt resistor (iS_SHUNT)
Conclusions
The results of performed measurements show that commonly used in the industry, flexible RCCPs with bandwidths of up to 50 MHz might not be fully suitable for rapid switching SiC MOSFET power modules. In addition to mismatches during the current rising or falling phase, the obtained current waveforms suggest not-existing high-frequency oscillations. Moreover, the waveforms might be distorted due to the susceptibility of RCCPs to the electromagnetic interferences that occur during fast switching processes. On the other hand, using CCSRs in power loops significantly changes the parasitic parameters of the power loops, directly influencing the switching behaviors. That shows the necessity for further research and development of flexible RCCPs featuring higher bandwidth with better immunity to electromagnetic interferences. At the moment, RCCPs seem to be the most suitable solution, but the possible errors and mismatches must be kept in mind when the performance of SiC power modules is evaluated.
REFERENCES
[1] Robles E., Matallana A., Aretxabaleta I., Andreu J., Fernandez M., Martin J., The role of power device technology in the electric vehicle powertrain, International Journal of Energy Research, vol. 46, Issue 15, 22222-22265 [2] Yadlapalli R., Tagore K., Anuradha K., Rajani K., Chandra S., A review on energy efficient technologies for electric vehicle applications, Journal of Energy Storage, vol. 50, Issue January, 104212 [3] Comyn R., SiC Power Device Competitive Landscape: A Patent Perspective, PCIM Europe 2023, 09 – 11 May 2023, Nuremberg [4] Kumar A., Moradpour M., Losito M., Franke W., Ramasamy S., Baccoli R., Gatto G., Wide Band Gap Devices and Their Application in Power Electronics, Energies 2022, vol. 15, 9172 [5] Rąbkowski J., Harasimczuk M., Kopacz R., Sobieski R., Three-Level Interleaved Non-isolated DC/DC Converter as a Battery Interface in an EV Charging System with Bipolar DCLink, Przegląd Elektrotechniczny, 2023, Issue 5, 202 [6] Helsper M., Ocklenburg M., SiC MOSFET Based Auxiliary Power Supply for Rail Vehicles, 20th European Conference on Power Electronics and Applications (EPE’18 ECCE Europe), 2018, 1-8 [7] Shepard P., 175 kVA SiC Converters in the New Dragon 2 Locomotive, 2018, Online. Available: https://eepower.com/news/175kva-sic-converters-in-the-newdragon-2-locomotive/ (Accessed 2022-07-21) [8] Lindahl M., Velander E., Johansson M. H., Blomberg A., Nee H., Silicon Carbide MOSFET Traction Inverter Operated in the Stockholm Metro System Demonstrating Customer Values, 2018 IEEE Vehicle Power and Propulsion Conference (VPPC), 2018, 1-6 [9] Biliński J., The latest generation drive for electric buses powered by SiC technology for high energy efficiency, MATEC Web of Conferences, vol. 180 (2018) [10] Telford M., SiC power device market rising 41.4% to $2.28bn in 2023, Semicontuctor Today, compounds & advanced silicon, vol. 18, 2023, March, Issue 2, 6-6 [11] Power Electronics Measurements, Online. Available: https://www.pemuk.com/products/cwt-currentprobe/cwtmini50hf.aspx (Accessed 2023-07-29). [12] Effective Measurement of Signals in Silicon Carbide (SiC) Power Electronics Systems, application note, Online. Available: https://download.tek.com/document/Effective-Measurement- SiC-Power-Systems_48W-73812-0.pdf (Accessed 2023-09-30). [13] Microchip Microsemi MSCSM120AM042CT6LIAG SiC MOSFET power module datasheet, Online. Available: https://www.microchip.com/en-us/product/MSCSM120AM042CT6LIAG-Module (Accessed 2023-07-29). [14] Zięba D., Rąbkowski J., Problems related to the correct determination of switching power losses in high-speed SiC MOSFET power modules, Bulletin of the Polish Academy of Sciences: Technical Sciences, vol.70, 2022, Issue 2 [15] Zięba D., Rąbkowski J., Dynamic performance evaluation of ultra-fast SiC MOSFET power module – a comprehensive approach, Przegląd Elektrotechniczny, 2023, Issue 5, 190 [16] Zhang Z., Guo B., Wang F., Jones E., Tolbert L., Methodology for Wide Band-Gap Device Dynamic Characterization, IEEE Transactions on Power Electronics, vol. 32, Issue 12, 9307–9318 [17] T&M Research, Current Viewing Resistors, Online. Available: https://www.tandmresearch.com/index.php?page=products (Accessed 2023-07-29) [18] Pearson Electronics, Pearson Current Monitor, Online. Available: https://www.pearsonelectronics.com/pdf/7713-03.pdf (Accessed 2023-07-29). [19] Rogowski W., Steinhaus W., Die Messung der magnetischen Spannung, Archiv fur Elektrotechnik, vol. 1, 1912, Issue 4, 141-150 [20] Samimi M., Mahari A., Farahnakian M., Mohseni H., The rogowski coil principles and applications: A review, IEEE Sensors Journal, vol. 15, 2015, Issue 2, 651-658[19] Ma H., Yang Y., Wu L., Wen Y., Li Q., Review of the designs in low inductance SiC half-bridge packaging, IET Power Electronics, vol. 15, 2022, Issue 11, 989-1003
Authors: Dawid Zięba, Medcom Company, Jutrzenki 78A, 02-230 Warsaw, E-mail: dawid.zieba@medcom.com.pl; Jacek Rąbkowski, Warsaw University of Technology, Institute of Control and Industrial Electronics, Koszykowa 75, 00-662 Warsaw, E-mail: jacek.rabkowski@pw.edu.pl.
Source & Publisher Item Identifier: PRZEGLĄD ELEKTROTECHNICZNY, ISSN 0033-2097, R. 100 NR 7/2024. doi:10.15199/48.2024.07.01
Published by Wiktoria GRYCAN, Wroclaw University of Science and Technology, ORCID: 0000-0001-8121-7612
Abstract. Prosumerism is inherently designed to be a tool that alleviates the grid. Still, not every prosumer aligns the consumption profile with the energy generation profile in photovoltaic installations. Therefore, the rapid development of Renewable Energy Sources (RES) in Poland, especially photovoltaic installations, has changed the energy generation structure, altering the working conditions in the grid. This work aims to identify how the current legislative support affects the profitability of RES and to determine how they should be adjusted to encourage investment in the right groups of recipients from the point of view of the security of the energy network.
Streszczenie. Prosumeryzm jest z założenia narzędziem, mającym na celu odciążenie sieci energetycznej. Jednakże, nie każdy prosument dostosowuje swój profil zużycia do profilu wytwarzania energii w instalacjach fotowoltaicznych. Dlatego też, wzmożony rozwój Odnawialnych Źródeł Energii (OZE) w Polsce, zwłaszcza instalacji fotowoltaicznych, zmienił strukturę wytwarzania energii, co wpłynęło na warunki pracy sieci. Celem tej pracy jest zidentyfikowanie, w jaki sposób obecne wsparcie legislacyjne wpływa na opłacalność OZE i określenie, w jaki sposób należy je dostosować, aby energię wytwarzały właściwe, z punktu widzenia bezpieczeństwa sieci energetycznej, grupy odbioców. (Wsparcie legislacyjne dla energetyki prosumenckiej w ramach bezpieczeństwa elektrycznego sieci elektroenergetycznej)
Keywords: prosumers, energy consumption, dynamic tariffs, photovoltaics Słowa kluczowe: prosumenci, zużycie energii, taryfy dynamiczne, fotowoltaika
Introduction
Due to the European Union’s ‘green energy goals,’ the number of photovoltaic installations in Poland has steadily increased. By January 2023, their installed capacity had reached 12.1 GW [1], 50% of the maximum power demand in the Polish energy system in 2022, which was 24.9 GW [2]. The installed capacity of solar panels has exceeded expectations and forecasts.
The 2030 goal, as outlined in ‘Poland’s Energy Policy until 2040,’ [3] aimed for a 32% share of all Renewable Energy Sources (RES) and at least 40% by 2040 in net electricity production by 2030. This goal has already been achieved thanks to incentives encouraging renewable energy installations. Numerous financial support programs [4], such as ‘Mój Prąd,’ ‘Czyste Powietrze,’ ‘Stop Smog,’ ‘Agroenergia’ for households, and ‘Energia Plus,’ ‘Przemysł energochłonny OZE,’ ‘Gwarancja Biznesmax,’ for businesses, have played a key role. These incentives, especially for households, typically take the form of grants, covering up to 50% of the investment costs, which has led to a significant growth of photovoltaics among this group.
In the existing low-voltage networks, the power flow has traditionally been unidirectional. Consequently, the grid and its protections were designed to ensure consumers a reliable power supply. Still, the evolving energy generation landscape is changing the working conditions, which has, due to the delayed grid modernization, caused various challenges. As reported by Kacejko and others [5], these challenges include exceeding quality thresholds for energy, such as higher harmonics, voltage fluctuations, and flicker indices. There have also been cases of surpassing permissible current values in power lines and transformers, exceeding voltage limits at network nodes, uncontrolled operation of micro installations during islanding, and improper functioning of protective devices.
Among these issues, the most significant problem highlighted by Kacejko and others [5] is the risk of voltage surges. This problem has been increasingly noticed in scientific publications [6,7] and by users of such installations [8]. The disconnecting of installations during voltage spikes [8] has made the issue particularly significant from a prosumer’s perspective, leading to numerous complaints [9].
In response to these issues, efforts are focused on the network’s operation and ensuring proper working conditions and safety. Various measures are being explored to maximize effectiveness while minimizing investment costs [5]. Rafał, Bielecki, and Skoczkowski [10], for instance, propose dynamic voltage regulation in the distribution network using inverters. At the same time, Cieślik suggests using power storage in stations for active power regulation [11]. Nevertheless, solving these issues at a national scale will require time and substantial investments.
In addition to local voltage surge problems, there is an increasing issue of energy overproduction in the network during peak sunlight hours [12,13]. Olczak and others [14] have highlighted the need to balance demand with temporary overproduction during maximum sunlight hours.
Prosumers should focus on selecting the installation capacity according to actual demand and adjusting their consumption to the generation profile. This adjustment can be achieved through individual energy management, such as load shifting over time using smart devices or energy storage instead of returning excess energy to the grid. Households do not widely adopt these actions, as they involve inconveniences, the need to modify habits, or significant additional financial costs.
Significant legislative changes resulting from the need to improve the operational security of the power grid are included in [15]. Document from December 2022 [15] has changed from a quantitative to a financial system for settling energy supplied to the grid to encourage prosumers to align their consumption with energy generation. Since next year (June 1, 2024), future changes may eventually allow energy settlement based on hourly rates (Chapter 2 Art. 4b.2 [16]), which would better reflect actual energy demand in the grid. Presently, it is the average monthly price for electricity generated from a renewable energy source and introduced into the electricity distribution network from July 1, 2022, to June 30, 2024 (Chapter 2 Art. 4b.1 [16]). Also, introducing the concept of a collective prosumer in the law [15] supports individual consumers who generate energy where it can be consumed at the time of generation. It encourages energy generation in multi-apartment buildings located in urban areas with significant energy demand.
This study aims to analyze how current and future legislative support impacts the profitability of RES in various consumer groups and how it can be further tailored to incentivize the right groups, considering the energy grid’s stability and safety.
Methodology
To estimate the generated energy, a tool available on the European Commission website, “Photovoltaic Geographical Information System,” was used [17]. Then, the consumption profiles of three companies were used. One location was adopted for all objects. In the enterprise analysis, generation from a 50kWp micro installation located in south-eastern Poland was first calculated. Company A is characterized by stable energy demand during the day and throughout the year (Fig. 1). Its demand is approximately 630 MWh/year. The energy demand for company B is approximately 100MWh/year. The highest demand occurs on working days between 6 a.m. and 4 p.m. (with a break at 11 a.m.). On weekends, demand drops by approximately 30% (Fig. 1). Company C consumes around 400 MWh/year annually. It works 24 hours daily, with the highest energy consumption between 8 a.m. and 10 p.m. (Fig. 1). Data on generation and consumption were compared, the amount of energy sent into the network was estimated, and the payback period was calculated, considering various types of support.
Fig.1. Enterprise A, B, and C. Data about usage and generation (annual average for each hour of the day). Installation 50kWp
Fig.2. Household. Data about usage and generation (annual average for each hour of the day). Installation 5kWp
Co-financing for renewable sources in the case of enterprises usually includes lower-interest loans or loan certificates. The most popular in 2023 include:
– Energy plus – for the reconstruction and connection of RES installations (loan up to 85% of eligible costs: from PLN 0.5 million to PLN 500 million, [18]
– Energy-intensive RES industry [19] – construction or reconstruction of a RES installation, along with connection to the power grid or plant, or with an energy storage facility (loan, up to 100% of eligible costs, in the amount from PLN 5 to 300 million, possibility of receiving a bonus of up to 30% of the amount paid, the need to use at least 80% of the energy generated for own needs),
– recruitment ended on May 10, 2023, therefore the tool was not taken into account in the analysis.
– FENG ecological loan – a subsidy of 20-70% for the repayment of the capital part of the loan – ELENA grant (modernization must reduce energy consumption by at least 30%) [20],
– White certificates
– construction of renewable energy installations and other pro-efficiency activities (possibility of selling the acquired certificate, subsidy depending on the current price of the certificate and the amount of energy saved
– required minimum amount of 116.3 MWh=1toe; replacement fee in 2023 was PLN 2,010/1toe) [16]
– funds from the KPO
– consider the research aspect of modernization activities or are in the process of being agreed upon. Hence, they will not be analyzed in this work.
The prepared analysis included an ecological loan (40% of the capital part) and a white certificate as tools that financially support the entrepreneur. It was assumed that enterprises would cover the investment from their own funds. In the case of companies A and C, which consume all the energy produced, the saving is the cost of energy that did not have to be purchased. In the case of company B, financial settlement (net billing) was included (with and without using the dynamic price).
The investment cost was estimated at PLN 300,000, using offers from external companies. The energy purchase price was adopted in three variants: I-PLN 794/MWh (average price for the second quarter of 2023), II-PLN 1,500/MWh, and III-PLN 2,000/MWh. Distribution fees were averaged between companies. The price of resale of electricity to the network was adopted in three variants: fixed and equal to the purchase price, fixed and lower than the purchase price, variable monthly price [21] depending on the time of day and season, and dynamic price [21]. Due to the volatility of prices in the energy market, these amounts may be underestimated and overestimated, which is why various variants were considered.
Further considerations were also made for the household. A facility located in the same town as the analyzed enterprises was selected. The annual electricity consumption for the domestic user is 4.1 MWh. The nature of consumption varies (Fig. 2) depending on the season (higher consumption in summer) and the time of day (highest consumption between 3 p.m. and 10 p.m.).
The amount and character of consumption on weekdays and weekends are similar. Three installation cases were assumed for the farm (5 kWp, 3 kWp, and 10 kWp). 10 kWp variant was adopted to check if the oversizing of prosumer installations is beneficial, according to current settlements (12 months to collect the financial deposit in the form of the volume of purchased energy, and after that time, a 20% refund of funds, Chapter 2. Art. 10a section 2 [16]). Data on generation and consumption were compared, the amount of energy given into the network was estimated, and the payback period was calculated, considering various types of support. Because the household does not use the entire volume of energy at the time of its production, and as it was written in the introduction, this may be an unfavorable phenomenon from the network’s point of view, an installation variant extended with energy storage was also considered. Financing for renewable sources for households mainly includes compensation and subsidies. In addition to regional programs, the basic program supporting renewable energy in households is “My Electricity.”
In 2023, the program was significantly modified [21]. The legislator rewards all activities that are intended to encourage self-consumption. The basic subsidy for the installation itself is up to PLN 6,000. PLN, but additional funds can be obtained for a heat pump (up to PLN 28,000), energy storage (up to PLN 16,000), solar collectors (up to PLN 3.5 thousand), and even an energy management system (up to PLN 3,000)). The co-financing cannot exceed 50% of eligible costs. The article assumes a variant involving obtaining funds for installation and energy storage. It was implicit that the maximum possible funding would be received. The installation cost and subsidy amounts were based on average offers from external entities, as in Tab. 1.
Table 1. The investment cost and founding amount used in calculations
.
The energy purchase cost was calculated assuming the current average price per MWh (including distribution), i.e., PLN 1000/MWh as variant I and PLN 1500/MWh as variant II. The energy sales price was adopted the same way as in the case of enterprises. It was decided to calculate a simple payback period. Yet, it would be advisable to consider the discount rate in the analyzed periods. The payback period is not the subject of consideration but only its comparison between individual variants. The time factor was not considered due to its dynamic nature and difficulty estimating changes over the last year.
Analysis
In the case of enterprises, the investment payback period is most influenced by the purchase price of electricity (Fig.3). This is also why, in 2022, companies were particularly interested in investing in renewable energy. As this price increases, the payback period decreases. For a price of PLN 2,000 (price level from the third quarter of 2022), the payback period is shortened to 2.5 years. The lowest price was PLN 794/MWh. For a lower price, the payback period would be extended.
When the sale price varies (dynamic prices), depending on the hour of the day and the season, the payback period is extended, although slightly (12%, i.e., eight months), because the company consumes 70% of the energy it produces.
Obtaining a white certificate with an investment of 50 kWp does not significantly impact the payback period (Fig. 4), regardless of the analyzed company. The most significant support is a grant to repay part of the capital under the FENG measure and the Elena grant (ecological loan). However, the modernization must bring at least 30% energy savings, so only company B could benefit from it. Depending on the funding obtained, the payback period decreases proportionally.
Companies, as prosumers, can use most of the energy produced by their installations. Therefore, the payback period of the investment is not influenced by the price of resale of energy to the grid. Due to the significant volume of energy consumed, they depend mainly on the purchase price. For enterprises, the payback period is most significantly influenced by subsidies for installations, which constitute the best incentive next to rising energy prices.
Fig.3. Investment payback period for A, B, and C enterprises depending on electricity price, installation power 50kWp
Fig.4. Investment payback period for A, B, and C enterprises depending on the form of support, installation power 50kWp
In the case of households and enterprises, the investment payback period (without additional stimulating factors) is similar. However, households often do not consume energy (unlike businesses) while producing it in a photovoltaic installation. This makes them much more sensitive to changes in energy prices and financial support mechanisms. An increase in the energy purchase price shortens the return on investment by approximately 30%. It is a regulated price until the first quarter of 2024, but it may rise even 100%. In the case of households, switching to net billing does not have a significant impact on the payback period of the investment (it extends it by a few months – Fig. 5). Still, as prices fall in situations of expected overproduction in future years, this system can significantly extend the payback period. The calculations used data from 2022, which were historically high. Households resell a small energy volume, and prices vary by about 30% between resale hours. It is difficult to predict how prices will develop, especially considering hourly price levels.
The settlement mechanism intended to prevent over-dimensioning of the installation works appropriately (Fig. 5). Each analyzed variant’s payback period for a 10 kWp installation is significantly longer. From the point of view of proper network operation, additional subsidies for energy storage installations are an essential supporting measure. Unfortunately, despite increasing funds for this purpose, an installation with storage still has a more extended payback period than an installation without it. The payback period is extended by at least one year. For prosumers’ motivation to make such investments, the opportunity of funding should be increased, e.g., to 70% of the costs.
Fig.5. Payback period for a household depending on the form of support and installation’s power
Conclusions
The analysis of the cases discussed in the article indicates the lack of equal support for photovoltaic installations in various groups of prosumers. Despite a similar payback period for installations without subsidies, households can count on more significant support than enterprises. Considering social policy and the financial capabilities of small entities such as households, we can understand the need for additional household support.
Yet, from a technical point of view, this action is unjustified. Its purpose is to ensure the safe and stable operation of the network. Often, companies have land that allows them to install renewable energy sources exactly where energy is consumed. The company’s investment in renewable energy sources not only does not generate the problem of power that is difficult to receive through the network but also reduces the company’s demand at the point of energy supply. Encouraging enterprises to make such investments seems justified, especially in making the subsidy dependent on the degree of use of the generated energy.
To sum up, more financial resources should be allocated to support enterprises investing in renewable energy sources. Additional programs should also be created to include subsidies and compensation in this group. At the same time, allocating more funds to support self-consumption in households seems justified. Shortening the payback period for installations with storage compared to installations that do not store energy would make it possible to popularize this type of solution. It is also worth considering making the subsidy amount dependent on the degree of use of the generated energy for one’s own needs.
To support entrepreneurs in building new renewable energy sources, it is also important to ensure stable regulations that enable investment planning over time. The introduced dynamic tariffs, although at current rates, do not significantly reduce the profitability of renewable energy – they are making predicting its profitability very difficult.
REFERENCES
[1] Ministry of Climate and Environment. Agencja Rynku Energii S.A., Statistical information on electricity. Monthly Bulletin, No.1(349), January 2023. [2]PSE-https://www.pse.pl/obszary-dzialalnosci/krajowy-systemelektroenergetyczny/zapotrzebowanie-kse, accessed 25.07.2023. [3] Ministry of Climate and Environment, Poland’s Energy Policy until 2040r., Warszawa 2021. https://www.gov.pl/web/klimat/polityka-energetyczna-polski, accessed 25.07.2023 [4]https://enerad.pl/aktualnosci/fotowoltaika-dofinansowanie2023-lista-aktualnych-dotacji/, accessed 25.07.2023 [5] Kacejko P., Adamek S., Wancerz M., Jędrychowski R., Ocena możliwości opanowania podskoków napięcia w sieci nn o dużym nasyceniu mikroinstalacjami fotowoltaicznymi, Wiadomości elektrotechniczne, 9 (2017). [6] Topolski Ł., Wojciech Schab W., Andrzej Firlit A., Krzysztof Piątek K., Analiza wpływu generacji rozproszonej na wybrane parametry jakości en. elektrycznej w sieci nn na terenie klastra Wirtualna Zielona Elektrownia Ochotnica, Przegląd Elektrotechniczny, 3 (2020), 17-20. [7] Mateusz Dutka M., Krzysztof Piątek K., Tomasz Siostrzonek T., Szymon Barczentewicz Sz., Bogusław Świątek B., Symulacja wpływu odnawialnych źródeł energii na zmienność wartości skutecznej napięcia sieci dystrybucyjnej, Przegląd elektrotechniczny 5 (2020), 26-29. [8]https://enerad.pl/aktualnosci/za-wysokie-napiecie-w-sieci-afotowoltaika-co-trzeba-wiedziec/, accessed 25.07.2023 [9]https://muratordom.pl/instalacje/fotowoltaika/dlaczegofotowoltaika-nie-dziala-prosumenci-zglaszaja-reklamacje-dooperatorow-jak-rozwiazac-problem-z-pv-aa-9R19-mMkaf1fJ.html accessed 25.07.2023 [10] Rafał K., Bielecki S., Skoczkowski T., Dynamiczna regulacja napięcia w sieci rozdzielczej, Przegląd elektrotechniczny, 5 (2016), 49-53 z wykorzystaniem falowników generacji rozproszonej [11] Cieślik S. Nowa rola stacji elektroenergetycznych w sieciach dystrybucyjnych niskiego napięcia. Elektroenergetyka Nr 242- 243, 2019, 3-15. [12]https://biznes.interia.pl/gospodarka/news-nadprodukcja-energiiz-oze-operator-odlaczyl-od-sieci-czesc-,nId,6736549 accessed 25.07.2023 [13]https://energia.rp.pl/oze/art38374801-stan-zagrozenia-dostawpradu-za-duzo-energii-ze-slonca accessed 25.07.2023 [14] Olczak P., Przemysław Jaśko P., Kryzia D., Matuszewska D., Fyk M.I., Artur Dyczko A., Analyses of duck curve phenomena potential in Polish PV prosumer households’ installations, Energy reports, 7 (2021), 4609-4622. [15] Act of January 27, 2022, amending the Act on Renewable Energy Sources and the Act amending the Act on Renewable Energy Sources and certain other acts, Dz.U. 2022 poz. 467 [16] Act of February 20, 2015, on renewable energy sources, Dz.U. 2015 poz. 478 [17] https://re.jrc.ec.europa.eu/pvg_tools/en/ stan na dzień 25.07.2023 [18] https://www.gov.pl/web/nfosigw/nabor-iv-wnioskow-2023-2024 stan na dzień 25.07.2023 [19] https://www.gov.pl/web/nfosigw/przemysl-energochlonny—ozestan na dzień 25.07.2023 [20]https://www.bosbank.pl/kredyt-ekologicznyfenggclid=Cj0KCQjw2eilBhCCARIsAG0Pf8s5CDDw4A1LLCA0sXKlgVEiBb0dYlcruDJpbsb8VNqrA6iBLLEHl8aAlvGEALw_wcB&gclsrc=aw.ds [21] http://www.pse.pl stan na dzień 25.07.2023 [22] https://www.gov.pl/web/klimat/rusza-piata-edycja-programumoj-prad stan na dzień 25.07.2023
Authors: dr inż. Wiktoria Grycan, Politechnika Wrocławska, Katedra Energoelektryki, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, E-mail: wiktoria.grycan@pwr.edu.pl;
Source & Publisher Item Identifier: PRZEGLĄD ELEKTROTECHNICZNY, ISSN 0033-2097, R. 100 NR 2/2024. doi:10.15199/48.2024.02.12
Published by Samira KHANAHMEDOVA, Azerbaijan State Oil and Industry University ORCID: 0000-0001-8862-1570
Abstract. The article discusses ways to reduce losses to increase efficiency in electric machines. The amount of energy loss is determined by the efficiency coefficient. The issues of changing the size of an electric machine under electromagnetic loads with a constant power source and constant voltage are considered. It is taken into account that reducing energy losses reduces the degree of environmental pollution, which contributes to improving life around the world. The analysis of the dimensions of an electric machine is given, that is, the possibility of reducing electricity losses by changing its dimensions within possible limits, taking into account the design capabilities of electric machines. The analysis is based on the law of similarity, which is widely used in the design of electric machines.
Streszczenie. Rozważane są kwestie zmiany wielkości maszyny elektrycznej pod obciążeniem elektromagnetycznym ze stałym źródłem zasilania i stałym napięciem. Bierze się pod uwagę, że zmniejszenie strat energii zmniejsza stopień zanieczyszczenia środowiska, co przyczynia się do poprawy życia na całym świecie. Podano analizę wymiarów maszyny elektrycznej, czyli możliwość zmniejszenia strat energii elektrycznej poprzez zmianę jej wymiarów w możliwych granicach, biorąc pod uwagę możliwości konstrukcyjne maszyn elektrycznych. Analiza opiera się na prawie podobieństwa, które jest szeroko stosowane w projektowaniu maszyn elektrycznych. (Niektóre zagadnienia dotyczące zwiększania wydajności maszyn elektrycznych)
Keywords: efficiency, electromechanical energy, electric motor, mass of the active part. Słowa kluczowe: sprawność, energia elektromechaniczna, silnik elektryczny, masa części aktywnej.
Introduction
The increase in efficiency in the process of electromechanical energy conversion is an urgent and technically difficult issue for all types of electric machines. 99% of all electricity generated is obtained through electric generators – by converting mechanical energy into electrical energy. Electric motors convert 65% of this energy back into mechanical energy. It should be noted that the distribution energy is spent on losses in the system elements (power lines, transformers and cables) in the amount of 10% of the energy at a distance from the source (power plant) to the actuator. Thus, the issue of reducing electricity losses remains relevant [1, 2, 6, 11].
This issue remains a complex technical and economic issue and the decision must take into account the cost of the electric motor. The cost of an electric machine depends primarily on the materials used, which determine the type, size and characteristics of the machine, and also depend on the economy of the state (the country from which the machine is made). Suppose losses in the machine are reduced by increasing its dimensions. In that case, it is necessary to consider comparing prices for materials used and labor costs in combination with electricity (saving electricity during engine operation). A sharp disproportionate increase in electricity prices compared to the prices of electric machines and other electrical equipment also affects the change in the principles of designing electric machines [3, 4, 7, 9, 11].
The solution of the task
For the design of electric machines and ensuring efficient operating modes, much attention is paid to the possibilities of increasing the efficiency, and the issues of changing its size under electromagnetic loads at a constant power source and constant voltage are considered. In addition, it must be borne in mind that reducing energy losses reduces the degree of environmental pollution, which contributes to improving life around the world [12, 21].
When analyzing the dimensions of an electric machine, that is, the possibility of reducing electricity losses by changing its dimensions within possible limits, it should be borne in mind that it is necessary to take into account the design capabilities of electric machines. The analysis is based on the law of similarity, which is widely used in the design of electric machines.
Main part
According to the similarity theory, when the linear dimensions of the active part of an electric machine change by “a” times, the inner diameter of the stator core Dd and the outer diameter Dx, the length of the stator core l1, the total length of the wires l2 and the polar distribution 𝜏q will change proportionally by “a” times [12, 15, 18, 24].
.
where .˙. – the sign of proportionality. The cross-sectional area of the copper in the Sy slot and the cross-section of the magnetic conductor, see the change in linear dimensions proportional to the square “a”:
.
The mass of the active part of the copper plate m1 and the mass of the magnetic conductor m2 are proportional to the cubic degree of change in linear dimensions:
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For analysis in the initial approximation, it can be taken into account that the dimensions of the inactive parts of the electric machine (housing, cushions, shaft …) do not increase proportionally to the increase in the volume of the active parts of the machine [7, 23]. The weight of the machine, the materials used and the labor costs are also proportional to the volume of the machine in the first approximation.
Considering the above, by increasing the size of the active parts of the asynchronous machine, let’s look at the analysis of the possibility of increasing the efficiency. Thus, the electrical and mechanical ratings – power, voltage, speed, type of protection and cooling – remain unchanged. In this case, according to similarity theory, when the linear dimensions of the machine change by a factor of “a”, the electromagnetic charges, induction B and current density y will change as follows [11, 17, 23]:
.
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If the rated voltage of the motor is constant, and if the density of induction and current changes in accordance with expressions (4) and (5), then the number of windings of the stator coil will change as follows,
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for an electric machine whose dimensions are increased by a factor of “a”, the losses in the windings PS, steel PP, and the main electromagnetic loads B vary depending on expressions (4) and (5) and are calculated by the following expressions:
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where PS and Pd – the corresponding losses of the machine in question. The efficiency of the engine is calculated:
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where P – the mechanical rated output power of the engine; Pp – the total losses in the machine, including losses in the stator and rotor; Ps – losses in steel.
Note that mechanical friction losses and ventilation losses depend on the size change. In this case, the dependences of electromagnetic charges and the number of windings of phase N on the indicator “n” and the coefficient of change in linear dimensions from the indicator “a” are shown in Table 1.
Table 1. Indicators of the number of windings of electromagnetic charges and phase
.
According to the expression (9), changes in the efficiency coefficient are performed for two industrially significant engines. The first engine (A) was mass-produced of industrial significance, the quantity data is taken from the reference table; the second engine (B), having high power, the quantity data is taken from the reference book. The rated power of the engine (B) is also more than 100 times the power of the engine (A). Nominal numbers of engines under investigation:
For comparative analysis, it is necessary to analyze the dependence of the efficiency coefficient on the parameters “a” and “n” for electrical machines (A) and (B). The main calculations are performed in the MATLAB/Workspace program.
a=1;1.05;1.1;1.15;1.2; 1.25;… n=0:0.05:2 % for engine A P=22; V=400V; f=50; 2p=2; P1=1098 % for engine B P=2500; V=6000V; f=50; 2p=2; P1=202 % efficiency teta=P./(P+P1) teta (A)=22000/22980+1098a+597a teta (B)=2500/2530.8+31.259a+201a
The results obtained are shown in Table 2 and 3. Based on the table, it obtains characteristics for comparative analysis.
Table 2. Results of calculations of efficiency coefficients for the engine (A)
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Table 3. Results of calculations of efficiency coefficients for the engine (B)
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The characteristics for the engine (A) and engine under study (B) are shown in the fig.1 and fig.2.
It can be seen from Figures 1 and 2 that the efficiency depends on the linear dimensions of the engine (value “a”) and the change in electromagnetic loads in and (parameter “n”). For each case, you can find the maximum function.
The efficiency coefficient for the engine (a) can be increased by 3.171%, provided that the linear dimensions are increased by 2 times and (N=2) losses are reduced by 18.5%. At the same time, the mass of active materials increases by 8 times.
Fig.1. The characteristics for the engine (A)
From Table 2 and Fig. 2, it can be concluded that with linear similarity of the efficiency coefficient 2p=2, the efficiency coefficient only increases. This is because the efficiency increases with increasing rated power, which is confirmed by the theory of similarity (electric machines and transformers).
Fig.2. The characteristics for the engine (B)
Conclusion
The article analyzes ways to reduce losses to increase efficiency in electric machines. The issues of changing the dimensions of an electric machine under electromagnetic loads with a constant power source and constant voltage are considered. The analysis of the dimensions of an electric machine is given, that is, the possibility of reducing electricity losses by changing its dimensions within possible limits, taking into account the design capabilities of electric machines. The analysis is based on the law of similarity, which is widely used in the design of electric machines.
A comparative analysis was performed for a commercially available engine and a high-power engine under study. The dependence of the efficiency coefficient on the parameters “a” and “n” for electric machines is analyzed. The main calculations were performed in the MATLAB/Workspace program.
The efficiency of the engine under study can be increased by 3.171%, provided that the linear dimensions are increased by 2 times and (N=2) losses are reduced by 18.5%. At the same time, the mass of active materials increases by 8 times.
With a linear similarity of the efficiency coefficient 2p=2, the efficiency coefficient only increases. This is because efficiency increases with an increase in rated power, which is confirmed by the similarity theory).
REFERENCES
[1] S. A Celtek, S.Ruşen, G. Karanfil Effects of Electric on the energy efficincy. Department of Energy Systems Engineering, Karamanoğlu Mehmetbey University, Karaman. 8th International Ege Energy Symposium and Exhibition, 2016, https://www.researchgate.net/publication/313767458_Effects_of_ElectricMotors_On_The_Energy_Efficiency [2] A. T. De Almeida, F. J. T. E. Ferreira, J. A. C. Fong, and C. U. Brunner, “Electric motor standards, eco-design and global market transformation,” Conf. Rec. – Ind. Commer. Power Syst. Tech. Conf., pp. 1–9, 2008. [3] S.M. Lu, “A review of high-efficiency motors: Specification, policy, and technology,” Renew. Sustain. Energy Rev., vol.59, pp. 1–12, 2016. [4] A. Zabardast and H. Mokhtari, “Effect of high-efficient electric motors Celtek et al. / 8th International Ege Energy Symposium and Exhibition – 2016 on efficiency improvement and electric energy saving,” 3rd Int. Conf. Deregul. Restruct. Power Technol. DRPT 2008, no. April, pp. 533–538, 2008. [5] “World Energy Outlook 2016, “IEA, Paris, License: CC BY 4.0 (report); CC BY NC SA 4.0 (Annex A), 2016. [Online]. https://www.iea.org/reports/world-energy-outlook-2016. [6] “Energy Efficiency 2022” IEA, Paris, 2022, vol. License: CC BY 4.0. https://www.iea.org/reports/energy-efficiency-2022. [7] “World Energy Outlook 2022, “IEA, Paris, License: CC BY 4.0 (report); CC BY NC SA 4.0 (Annex A), 2022. https://www.iea.org/reports/world-energy-outlook-2022. [8] “Electric motors and variable speed drives” https://commission. europa.eu/energy-climate-changeenvironment /standards-tools-and-labels/products-labellingrules-and-requirements/energy-label-and-ecodesign/energyefficient-products/electric-motors-and-variable-speeddrives_en (accessed 21/04/2023, 2023). [9] “Energy Efficiency Improvements in Electronic Motors and Drives,” 2000, https://doi.org/10.1007/978-3-642-59785-5. [10] Kazovskiy Ye.YA. Perekhodnyye protsessy v elektricheskikh mashinakh peremennogo toka- M.L.: Izd. ANSSSR, 1962.-624 s. [11] Jacek F. Gieras Electrical Machines 1st Edition. CRC Press; December 18, 2020, 452 pages. ISBN-10: 0367736942. [12] Ryszard Palka and Marcin Wardach , Design and Application of Electrical Machines. May 2022., Pages: 352. https://doi.org/10.3390/books978-3-0365-4324-6 [13] Postnikov N.M., Ostapchuk L.B., Postnikov V.N. Godograf toka i parametry massivnogo rotora asinkhronnoy mashiny // Elektrichestvo, -1975.-№1, pp.38-42 [14] Paul C. Krause, Oleg Wasynczuk, and Scott D. Sudhoff.. Analysis and Design of Electric Machines. Publication date: 2013. Publisher: Wiley. 720 pages. [15] T.J.E. Miller. Synchronous and Asynchronous Machines. Pergamum Press.1989. 448 pages [16] R.Saidur. A review on electrical motors energy use and energy savings. Renewable and Sustainable Energy Reviews, Volume 14, Issue 3, April 2010, Pages 877-898 [17] L Nagel. What is the Average Efficiency of an Electric Motor, July 02, 2023, https://www.tytorobotics.com/blogs/articles/what-is-theaverage-efficiency-of-an-electric-motor [18] Wilde, C. U. Brunner,”Energy-Efficiency Policy Opportunities for Electric Motor-Driven Systems”, International Energy Agency, Working paper, 2011. [19] “Electric Motors and Variable Speed Drives – Standards and legal requirements for the energy efficiency of low-voltage three-phase motors”, ZVEI – Zentralverband Elektrotechnikund Elektronikindustrie e.V., Division Automation – Electric Drive Systems, Frankfurt, December 2010, 2nd Edition. [20] Vagati, “The synchronous reluctance solution: a new alternative in AC drives,” 20th International Conference on Industrial Electronics, Control and Instrumentation, 1994. IECON ’94., Bologna, 1994, pp. 1-13 vol.1. [21] Lipo, T. A., “Synchronous reluctance machines – a viable alternative for AC drives.”, Wisconsin Electric Machines and Power Electronics Consortium, Research report, 1991. [22] “Low voltage Process performance motors according to EU MEPS”, ABB catalog, October 2014 [23] “Rare Earths”, S. Geological Survey, Mineral Commodity Summaries, January 2016. [24] Guglielmi, B. Boazzo, E. Armando, G. Pellegrino and A. Vagati, “Magnet minimization in IPM-PMASR motor design for wide speed range application,” 2011 IEEE Energy Conversion Congress and Exposition, Phoenix, AZ, 2011, pp. 4201-4207. [25] “Motor technologies for higher efficiency in applications – An overview of trends and applications”, Danfoss Power Electronics – Danfoss VLT drives PE-MSMBM, November
Authors: Khanakhmedova Samira Alkhadi. Doctor of Philosophy in Engineering, Associate Professor of the Electromechanics Depart- ment of the Azerbaijan State University of Oil and Industry. Baku city, Azadlyg avenue 20,Email: samira.khanahmedova@asoiu.edu.az.
Source & Publisher Item Identifier: PRZEGLĄD ELEKTROTECHNICZNY, ISSN 0033-2097, R. 100 NR 9/2024. doi:10.15199/48.2024.09.32
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