Existence of Electrical Pollution

Published by

  • Puneet Chawla, Assistant Professor, Electrical Eng. Department, Ch. Devi Lal State Institute of Eng. & Tech., Panniwala Mota (Sirsa)
  • Rajni Bala, Lecturer, Electrical Eng. Department, Ch. Devi Lal State Institute of Eng. & Tech., Panniwala Mota (Sirsa)

ABSTRACT

Power Quality is deteriorating continuously in developed countries. Poor power quality, also known as dirty electricity, ubiquitous pollutant, refers to a combination of harmonics and transients generated primarily by electronic devices and by non-linear loads. It flows along wires and radiates from them and involves both extremely low frequency electromagnetic fields and radio frequency radiation. Until recently, dirty electricity has been largely ignored by the scientific community but dirty electricity is adversely affecting the lives of millions of people.

Recent inventions of metering and filter equipment provide scientists with the tools to measure and reduce dirty electricity on electrical wires. Several case studies and anecdotal reports are presented regarding the existence of electrical pollution in this paper.

Keywords: Electrical pollution, dirty electricity, surge voltage, floating neutral, arc flash hazards, harmonics, electromagnetic spectrum, flickering, flick meter, Graham-Stetzer (GS) meter and GS filters.     

INTRODUCTION

Electrical pollution is not something you can see, smell, taste, or touch. It is not something that you can sense, making it difficult for one to be aware of the presence of electrical pollution. With this in mind, it is important to understand what causes electrical pollution and what to look for in our everyday environment and home.

Electrical pollution”[1] is a misused and misunderstood term that has no basis in engineering or electrical science. There are a variety of normally occurring electrical phenomena that arise from our everyday use of electricity. “Electrical pollution” is being loosely used to describe these phenomena. These electrical phenomena include:

  1. Stray voltage
  2. Electric and magnetic fields
  3. Earth currents
  4. Transients and high frequency noise
  5. Harmonics
  6. Flickering
  7. Surge Voltages
  8. Lightning  
  9. Floating Neutral on power system

Stray voltage is current from on and off farm sources. Stray voltage on farms has been detected by observing behavioral changes in farm animals and some health problems for humans. This is often a localized condition due to poor grounding of the farm or utility electrical system, or a failure of some electrical application.

Electric and magnetic fields, or EMF are weak, invisible fields of energy that exist around anything that carries or uses electricity. The strength of these fields quickly decreases as you move away from the source.

Earth currents are very low magnitude electrical currents that can be detected in the soil. Natural activity such as movement of magma deep within the earth and solar flares create some of these currents, while the delivery and use of electrical energy create others.  Most of the earth currents are the result of local electrical loads by the end consumer of electrical power.

Transients and high frequency noise on the wiring of our homes and businesses are created by the use of modern electronic devices such as radios, televisions, cell phones and microwaves. This “noise” is normally very small (a tiny fraction of one volt) compared to the standard 120 volts at a typical wall outlet. As with earth currents, the source of transients and high frequency noise is primarily the end user. Because of the design of the electrical distribution system, this noise cannot be transmitted very far from its source. We occasionally experience this noise as momentary interference (snow) on a television screen or a fuzzy buzz in our communications systems.

Electromagnetic spectrum


Dirty Electricity from 2 kHz-150 kHz (transient bursts)

Harmonics is a component of waveform of alternating current of a frequency which is a multiple of fundamental current is called harmonic component.

The quality of power can be simply defined with parameters as below:

  1. The supply voltage should be within guaranteed tolerances of declared value. A lower voltage called a sag and a high voltage are undesirable, long duration of cut offs are to be abhorred up to 10%.
  2. The supply frequency must lie within guaranteed parameter of 3% in the country.
  3. The wave should be a pure sine with allowable limits for distortion.
  4. Sudden voltage distortion must be contained.
  5. Supply of three phases of a 3-Φ system should be balanced.
  6. The earthing system should serve its purpose satisfactory.

The utility’s main duty is that to provide the electricity which satisfy all above factors. Bu the harmonic injection by various industries is the main reason of bad quality of power.

Flicker is defined as the impression of unsteadiness of the visual sensation induced by a light stimulus whose luminance or spectral distribution fluctuates with time. It is caused by the voltage variations in the electrical power system and brings annoyance to human beings. The human eye is the most important responder to the light.

There is a lamp-eye-brain model built called as IEC flickmeter. It is able to simulate the physiological sensitivity of the human eye that is subjected to are reference incandescent lamp of 60W, 230V.

Lightning and Surge Voltages Overvoltages are designed as transient voltages at transient surges. This means that they are short-lived, temporary oscillations. Their shape and frequency depends on the impedance of the circuit. A transient surge is a sudden (shorter than a milliseconds) rise in the flow of power. Voltages can peak up to 12 times the nominal system voltages. Transient surges result from a number of resources, the most common of which are internal, such as load switching and even normal equipment operations. In fact, 80% of transients are generated internally. External transient are the result of lightning and load switching by utilities and upstream facilities. Overvoltages are primarily caused by:

  1. Lightning due to atmospheric discharges.
  2. Transient Switching operations.
  3. Faulty Switching operations.
  4. Electrostatic discharges.

Floating Neutral If the star point of Unbalanced load is not joined to the star point of its power source (Distribution Transformer or Generator) then phase voltage do not remain same across each phase but it vary according to the unbalanced of the load.

As the potential of such as isolated Star point or Neutral point is always changing and not fixed s it is called as Floating Neutral. Power flows in and out of customers premises from the distribution network, entering via the phase and leaving via the neutral. If there is a break in the neutral, return path electricity may then travel by a different path. Power flow entering in one phase returns through remaining two phases. Neutral point is not at ground level but it floats up to Line voltage. This situation can be very dangerous and customers may suffer serious electric shocks if they touch something where electricity is present.

Broken neutrals can be difficult to detect and in some instances may not be easily identified. Sometimes broken neutrals can be indicated by flickering lights or tingling taps. If you have flickering in lamps, this may cause a serious injury or even death.

E-waste [2] The e-waste is influenced by several factors, but it can be broadly classified into two categories: E-waste Generated and E-waste imported.

The center of Science and Environment reports that the E-waste generated in the country ranges from 350,000 tones to 400,000 tones, where 50,000 tones of e-waste is illegally imported into the country every year. The growth of e-waste in the country is influenced by low end of life of electronic and electrical products due to frequent release of new models, reasonable and attractive prices, low refurbishing and most importantly lack of recycling infrastructure in the country. This is also due to the lack of balance between the wastes generated and recycled (252,868 MTA). The Indian government is in full swing to contain this situation through the implementation of Hazardous Wastes (Management, Handling and Transboundary Movement) Rules.

In these characterizations of electrical pollution, high frequency signals pollute regular electrical currents traveling in wires and currents through the earth. To better understand the background for the causes of electrical pollution, it is helpful to learn the basics of how the electrical current works.

Direct current is similar to battery power where current flows back and forth between energy terminals.

Alternating current is a wave-like movement of energy that oscillates back and forth, and the energy flows in the direction of the load. The rate of oscillation is defined as frequency. At an electrical grid base, the current oscillates at 50 times per second, or 50 Hz. Regular “clean” power enters homes, buildings, and offices at 50 Hz. The increased use of electrical power overloads electrical grid base, which distributes the power. Power is “dirty” or polluted when it contains the high frequency signals flowing through overloaded wires, and not just clean 50 Hz power.

The pollution of electricity is often compared to how water is polluted. At the source, water is clean. It is what comes with the water and pollutants along its path to the recipient that makes the water harmful to humans. However, like water pollution in many ways, electrical pollution is complex and often difficult to understand for the common consumer. The causes are varied and sometimes cannot be identified with certainty. However, the bulk of overloaded electricity bases can be attributed to the reliance on electrical appliances in today’s environment. In the 1950’s, the National Electrical Safety Code required a neutral wire to return wire to utilities. In this code it was forbidden to use the earth as a neutral return. This was a worsening problem in rural, farm areas where the currents were being returned to the soil affecting the feeding of animals. Later, the Public Service Commission allowed utilities to use grounding rods to serve as neutral wires for return. This was done instead of increasing the size of the neutral rods. Installing ground rods is a less costly solution than making the neutral rods larger in size.

The grounding rods serve as an alternate and additional pathway for the energy to return to the substation instead of to the earth. The use of electricity has dramatically increased in the past 50 years causing stress on the electrical infrastructure. Those concerned about electrical pollution say the size of neutral wires to make sure energy is returned to its source needs to be much larger. The current regulated size of the neutrals is not large enough to handle the load due to the greater use of electricity. The currents that are not properly directed are emitted into the environment or into homes or offices where electrical devices are widely relied upon by consumers.

Neutral wires are not often sized for the modern electrical load. Power that is misdirected into the earth or home environments contains a much higher frequency that the 50 Hz classification making it “dirty” or unclean. Knowing that consumers use a more significant amount of electricity in today’s modern environment, there is a concern that electrical pollution is affecting humans. Those concerned about electrical pollution advocate for stricter regulations and for the widespread use of filters to measure and control “dirty” electricity. Considering electrical pollution can come from a variety of sources, the subject is complex and there is still a lot to be learned on the topic. In the meantime, some technology has been created to measure and control electrical pollution. This is especially important for those who have realized they are “electrically sensitive” and are experiencing health problems which are attributed to electrical pollution.

ARC FLASH HAZARDS IN POWER SYSTEM [3]

The consideration of arc flash hazards is a relatively new concern for power system analysis, working and design. However, it is a concern that is rapidly momentum due to increasingly strict worker safety standards and system reliability requirements that demand work on live electrical equipment’s. Recently, enacted guidelines and regulations regarding arc flash hazards have focused power industry attention on quantifying the dangers of arc flash events n low and medium power electrical equipment. The arc flash hazard analysis is mandatory and more popular in European countries and US to ensure safety of the personnel working under live conditions. However, it is becoming popular in India as well so as to ensure the system reliability. Since the incident energy from an arcing fault is directly proportional to the arc clearing time, reducing the arc time is very beneficial. It results in reducing the personnel protective equipment (PPE) level requirements and limiting direct damage to the equipment.

An arcing fault is the flow of current through the air between the phase conductors or phase conductor & neutral ground. Arc flash is the ball of fire and molten metal as well as a pressure force or blast that explodes from an electrical short circuit. Electrical arcs from, which a medium that is normally an insulator, such as air, is subjected to an electric field strong enough to cause it to become ionized. This ionization causes the medium to become a conductor which carry the electric current. An arcing fault can release tremendous amount of concentrated radiant energy at the point of the arcing in a small fraction of a second, resulting in extremely high temperature, tremendous pressure blast and shrapnel hurling at high velocity.  Arc flash temperatures can easily reach 14,000 to 16,0000F (77600C to 88710C). These temperatures can be reached by a fault in several seconds. The heat generated by the high current flow may melt or vaporize the material and create an arc. This arc flash creates a brilliant flash, intense heat, and a fast moving pressure wave that propels the arcing products. Some of the effects of arcing fault include:

  1. Extreme heat, Pressure waves and Sound waves.
  2. Molten metal, shrapnel and vapor
  3. Intense light.

Arc flash is related to the available fault current and total clearing time of the over current protective device during a fault. It is not necessarily linear as lower fault currents can be sometimes result in a breaker or fuse taking longer to clear, thus extending the arc duration and raising the arc flash energy. To perform an accurate arc flash hazard analysis, a realistic value for three-phase bolted fault and total clearing time for the affected over current protective device must be known. Arc flash hazard analysis and study is required to be carried out in the installations where the worker is operating under live conditions.

Arc flash is measured in thermal energy units of cal /cm2 and for arc flash analysis is referred to as the incident energy of the circuit. 1.2cal/cm2 of thermal energy on a person’s skin for a short period of time generally produces a second degree burn. Second degree burn is considerably curable and painful and occur if the temperature of human skin is raised to 80oC for 0.1 seconds. Depending on the material clothing may ignite when temperature reach between 370-760oC (700-1400oF). if clothing and equipment are worn to limit the exposure of the worker to limits below those identified above, the worker should walk away from an accident with minimal injury.

Types of Faults A bolted short circuit occurs when the normal circuit current by-pass the load through a very low impedance path resulting in current flow that can be thousands of times the normal current. All equipment needs to have adequate interrupting ratings to safely contain and clear the high fault currents associated with the faults.

In contrast, the arcing fault is the flow of current through a higher impedance medium, typically the air, between phase conductors or between phase conductor and neutral or ground. Arcing fault currents can be extremely high in current magnitude approaching the short-circuit current but are typically between 38% to 89% of the fault. The inverse characteristics of typical over-current protective devices results in longer clearing time for an racing fault due to lower fault values. The amount of energy released during an arcing fault depends upon the voltage, the current and the duration of arc. The arc duration is dependent on the arcing fault current magnitude and the protective device settings. Due to its nature, the magnitude of an arcing fault is subject to many variables and is difficult to perfectly predict.

Causes of Electric Arc Arcs can be initiated by the following:

  1. Accidental touching.
  2. Accidental dropping of tools.
  3. Failure of insulating materials.
  4. Improperly designed or utilized equipment.
  5. Improper work procedures.
  6. Spark discharges.
  7. Over Current across the narrow gaps between conductors of different phases.
  8. Dust and impurities on insulating surfaces.
  9. Fumes or vapor of chemicals.
  10. Corrosion of equipment parts, thus weakens the contacts between terminals.
  11. Condensation of vapor and water dripping on the surface of insulating surface.

Reasons of Address arc Flash The following are the reasons to address the arc flash:

  1. Protect the workers from potential beam and prevent the loss of life.
  2. Comply with Occupational safety and Health Administration (PSHA) codes with National Fire Protection Association (NFPA) standards on employee safety, NFPA-70E.
  3. Prevent loss to organization through loss of skilled manpower, litigation fees, higher insurance costs.
  4. Increases production uptime by reducing accidents.

Classification of Hazard Risk category NFPA 70E defines 5 levels of risk category for arc flash hazard based upon the calculated indecent energy at the working distance. As per the risk category, different Personnel Protective Equipment (PPE) are required to be worn by the person working near to live equipment.

Table 1: Classification of Hazard Risk Category

CategoryEnergy LevelPPQ RequirementRemarks
0N/ANon-melting, flammable materials
15 cal/cm2Hard hat, Safety glasses or safety goggles. Hearing protection (ear canal inserts) Heavy duty leather glovesThe Hazard Risk category levels should be restricted up to category 2 as the PPE required to be worn are easy to work with.
2 8 cal/cm2 Hard hat, Safety glasses or safety goggles. Hearing protection (ear canal inserts)
Heavy duty leather gloves.
The Hazard Risk category levels should be restricted up to category 2 as the PPE required to be worn are easy to work with.
3 25 cal/cm2 Hard hat, Safety glasses or safety goggles. Hearing protection (ear canal inserts)
Heavy duty leather shoes.
Hazard Risk category of category 3 and category 4 shall not be recommended as the PPE used will be bulky.
4 40 cal/cm2 Hard hat, Safety glasses or safety goggles. Hearing protection (ear canal inserts)
Heavy duty leather shoes.
Hazard Risk category of category 3 and category 4 shall not be recommended as the PPE used will be bulky.

Benefits of performing Arc Flash study Below are some of the benefits of performing an accurate arc flash hazard analysis:

  1. Enhance the system reliability with proper protective device coordination study.
  2. Equipment evaluation analysis is very important.
  3. Since the system can be modeled on software, it will be very easy to make future changes or upgrade with minimal expense and efforts.
  4. Drastically lessen chances of having to make a very unpleasant visit.
  5. Provide the best possible PPE for workers and technicians.
  6. Possibly lower insurance premiums.
  7. Brings electrical system up to date by providing current one-line diagram.

Harmonics is a component of waveform of alternating current of a frequency which is a multiple of fundamental current is called harmonic component. The harmonic component of twice the fundamental frequency is called as second order harmonics and the triple frequency harmonics is triple harmonic component. Complex waveforms are produced due to superposition of sinusoidal wave of lowest frequency f ,i.e. fundamental frequency and waves of different frequencies whose frequency are an integral multiples of basic frequency, such as waves of frequencies 2f, 4f, 6f called as even harmonics and of 3f, 5f, 7f are called odd harmonics.

Types of harmonics various types of harmonics are

  1. Harmonic voltage distortion.
  2. Harmonic current distortion.
  3. Interchange voltage & current component.
  4. Subharmonic distortion

Voltage harmonic distortion which is generally present in supply of power from utility. The distortion of current waveform is called current harmonic distortion which is generally injected by the non-linear loads to supply the utility and corrupts it.

Non-Linear loads When the current drawn through the circuit is non sinusoidal even there is a pure sinusoidal supply from the utility, then the load is called as non-linear load. Some examples of non-linear loads are:

  1. Transformer saturation.
  2. Thyristor controlled equipments.
  3. Ac/dc, ac/ac, dc/ac converters.
  4. Battery chargers.
  5. Electronic and medical test equipment.
  6. PCs and office machines.
  7. Induction heaters.
  8. Synchronous machines (non-sinusoidal air gap flux).

Evaluation of Harmonic distortion Any real waveform can be produced by adding sine waves together. It can also be shown that this combination is unique. It may be note that fundamental and third harmonic component waveforms for two cases (in phase and out of phase) result in two waveforms with no change in amplitude. So, when the odd harmonics are in phase with fundamental component, distorted resultant waveform of square type wave and when harmonic is shifted by 900 phase, the distorted resultant becomes more like as a spikes.

Table 2: Evaluation of Harmonic distortion

Name/OrderFrequency SequenceRelative Voltage(%)
150+3
2100
315005
4200+
52506
63000
7350+5
8400
945001.5
10500+
115503.5
126000
13650+3.5
14700
1575003
178502
19950+1.5
21105000.5
2311501.5

Effects of harmonics The effects of harmonics on power system are as follow:

  1. Over voltages and excessive currents due to series and parallel resonance.
  2. Increase in losses and consequence heating of transformers and rotating machines.
  3. Overloading of power factor correction shunt capacitors leading to excessive current to fuse blowing.
  4. Ageing of insulation of the electrical equipments. Hence reduction of efficiency of power system.
  5. Increases errors in energy meters.
  6. Mal functioning of protective gears such as relays, circuit breakers.
  7. Inductive interference with neighboring communication network.
  8. Tripping of machines at smaller loads.
  9. Fire hazards

Sources of harmonics [4]: Harmonic pollution in power system is generally caused by non-linear loads. The sources of harmonics in power system can be classified as follows:

a) Harmonic originated at high voltages by supply authorities:

  1. HVDC system.
  2. Back to back system.
  3. Static VAR compensation system.
  4. Wind and Solar power converters with interconnection.

b) Harmonics originated at medium voltages like large industrial loads like Traction equipment, variable speed drives, thyristors controlled drives, induction heaters, Arc furnaces, Arc welding, capacitor bank, electronic energy controllers.

c) Harmonic originated at low voltages at consumers end like single phase loading, uninterrupted power supplier, semiconducting devices, CFL, solid state decies, domestic appliances and accessories using electric devices, electronics chokes, electronic fan regulators/light dimmers.

Solution for minimizing harmonic current effects [5]

  1. Over-sizing or derating of the installation- This solution does not eliminate harmonic currents flowing in the low voltage (less than 1000V AC) distribution system but masks the problems and avoid the consequences. The most widely implemented solution in a new installation is over sizing of neutral conductor.
  2. Specially connected Transformer- This solution eliminates 3rd order harmonic currents. It is centralized solution for a set of single phase loads.
  3. Series Reactors- This solution consists of connecting a reactor in series with non-linear load.
  4. Tuned Passive filters- A filter may be installed for one load or a set of loads. The filter rating must be coordinated with the reactive power requirements of the loads.
  5. Active harmonic filters- The active harmonic filters are used to introduce the current component to cancel die harmonic component of the non-linear loads, such as Series Filters, Parallel Filters & Hybrid Filters.

Lightning and Surge Protection [6]

Bolts of lightning exhibit extremely high currents. So, they cause a large voltage drop and accordingly, a large rise in potential even in well-earthed building or system despite low earthing resistance.

Overvoltages due to direct lightning strokes When lightning strikes a lightning conductor or the roof of a building which is grounded, the lightning current is dissipated in to the ground. The impedance of the ground and the current flowing through it create large difference of potential, this is called as overvoltage. This overvoltage then propagates throughout the equipment via the cables, damaging equipment and results in explosion.

Overvoltages due to indirect effects of lightning strokes Overvoltages are also produced lightning strikes in the vicinity of a building due to increase in potential of the ground at the point of impact. The electromagnetic fields created by the lightning currents generate inductive and capacitive coupling, leading to other overvoltages. Within a radius upto several kilometers, the electromagnetic field caused by the lightning in clouds can also create sudden increase in voltage. Thus causes, irreparable damage to the sensitive equipment’s such as fax machines, computer power supplies and safety & communication systems.

A lightning strike (direct or indirect) can have a destructive and disturbing effect on installations located up to several miles from the actual point of the strike. During a storm, underground cables can transmit energy from a lightning strike to equipment installed inside building. A lightning protection device such as lightning rods or Faraday cage, installed in a building to protect against the risk of a direct strike can increase the damage to electrical equipment connected to the main power supply near or inside the building.

Conducive coupling Overvoltages are transferred directly into circuits via common earthing impedances. The magnitude of the overvoltages depends on the ampereage of the lightning and the earthing conditions. The frequency and wave behavior are mainly determined by the inductance and speed of the current rise. Even distant lightning strikes can lead to overvoltages in the form of travelling waves which affect the different parts of electric systems by the conductive coupling.

Inductive coupling A high-ampere lightning strike generates a strong magnetic field. Starting from here, overvoltages reach nearby circuits by means of induction effects, according to the transformer principle, e.g. directly earthed conductor, power supply lines, data lines etc.

Capacitive coupling A capacitive coupling of overvoltages is also possible. The high voltage of the lightning generates as electric field of high electric strength. The transport of electrons  can cause a capacitive decay to circuits with lower potentials and raise the potential concerned to an overvoltage level.

Radiation coupling Electromagnetic wave fields (E/H field), that also ensue during lightning (distant field condition, E/H field vectors perpendicular to each other), affect conductor structures in such a  way that coupled overvoltages must be expected even without direct lightning strikes. Permanent wave fields from strong transmitters are also able to  cause coupled interference voltages in lines and circuits.

Lightning protection on Motors However, during lightning and switching of circuit breakers, re-strikes are pre-strikes during opening and closing of a circuit breaker may lead to a broad band frequency spectrum of overvoltages. Such overvoltages may have an oscillating character and lower amplitude at the Motor terminals. In addition they may arrive at the motor input without any changes in amplitude and waveform so the lightning arresters will not able to detect any overvoltage near the terminals as well as the input sides. If the oscillating frequency component of the external overvoltage is equal to the natural frequency of windings, then magnitude of the internal resonance overvoltage has its maximum value. So, overvoltages generated in transient and lightning strikes in electrical power equipment may be dangerous for insulating system despite the applied overvoltage protection. In order to ensure protection from transient surges, installation of lightning protective devices is a must.

Surge Protection Pumping stations are particularly vulnerable to lightning-induced voltage surges on incoming power lines, since it is characteristic of their operation to be in use during thunderstorms. So, special care should be taken to reduce the magnitude of these voltage surges to avoid major damage to the electrical equipment contained within. A small investment can greatly reduce voltage stresses imposed on rotating machines and switchgear by lightning-induced surges. There are two transient elements of a voltage surge that require different protective equipment. The protection of the major insulation to ground is accomplished by station surge arrestor which limit the amplitude or reflections of the applied impulse wave within the power windings

Medium voltage motors To obtain the most reliable protection of the motor’s major and turn insulation systems, a set of arrestor and capacitors should be installed as close as possible to the motor terminals. The arresters should be valve-type, station-class designed for protection. The leads from the phase of motor to the capacitor and from the capacitor to ground should be as short as possible.

Low voltage motors These are of 600V and below have relatively higher dielectric strength than medium voltage motor. Normally, when higher speed motors of this voltage class are connected through a transformer protected by Station-class arrester on the primary side, no additional protection is required. However, due to more expensive slower speed motors employed in pump stations, plus the critical nature of these motors, the minimal additional cost of lightning protection is required. A 3-phase valve-type low voltage arrester should be provided at the service entrance to the station and a three-phase capacitor should be provided at each motor terminal.

Surge capacitors [7] have been commonly used as protection device to mitigate transients. The combination of surge capacitors and surge arresters has been used to protect medium voltage motors from steep-fronted voltage surges. The purpose of using the surge capacitor is to reduce the rise time of the surge. The following points must be observed to guarantee fault-free operation of an electrical drive:

  1. Correct design, a suitable motor has to be selected for each application.
  2. Professional operation, professional installations and regular maintenance are preconditions for such operation.
  3. Good motor protection, this has to cover all possible problem areas:
  • It must not be tripped before the motor is put at risk.
  • If the motor is put at risk, the protection devices as to operate before any damage occurs.
  • If damage cannot be prevented, the protection, device has to operate quickly in order to restrict the extent of the damage as much as possible.

Impact of Floating Neutral in Power Distribution [8]

If the star point of Unbalanced load is not joined to the star point of its power source (Distribution Transformer or Generator) then phase voltage do not remain same across each phase but it vary according to the unbalanced of the load.

As the potential of such as isolated Star point or Neutral point is always changing and not fixed s it is called as Floating Neutral. Power flows in and out of customers premises from the distribution network, entering via the phase and leaving via the neutral. If there is a break in the neutral, return path electricity may then travel by a different path. Power flow entering in one phase returns through remaining two phases. Neutral point is not at ground level but it floats up to Line voltage. This situation can be very dangerous and customers may suffer serious electric shocks if they touch something where electricity is present.

Normal Power Condition and Floating Power Condition

Normal power condition On 3-Φ systems, there is a tendency for the star point and phases to want to ‘balance out’ based on the ratio of the leakage on each phase to earth. The star-point will remain close to 0V depending on the distribution of the load and subsequent leakage. 3-Φ systems may or may not have a neutral wire. A neutral wire allows the three phase system to use a higher voltage while still supporting lower voltage single phase appliances. In high voltage distribution situations it is common not to have a neutral wire as the loads can simply be connected between phases.

The neutral should never be connected to a ground except at the points at the service where the neutral is initially grounded (at Distribution Transformer). This can set up the ground as a path for a current to travel back to the service. Any break in the ground path would then expose a voltage potential. Grounding the neutral in a 3-Φ system helps stabilize phase voltages. A non-grounded neutral is sometimes called as floating neutral and has a limited applications.

Floating power conditions Power flows in and out of customers premises from the distribution network, entering via the phase and leaving the neutral. If there is a break in the neutral paths electricity may travel by the different path. Power flow entering in one phase leaves through the other two phases. Neutral point is not to ground level but it Floats up to Line Voltage. This situation can be very dangerous and customers may suffer serious electric shocks if they touch something where electricity is present. Broken neutrals can be difficult to detect and in some instances may not be easily identified. Sometimes broken neutrals can be indicated by flickering lights or tingling taps. If you have flickering in lamps, this may cause a serious injury or even death.

Various factors which cause Neutral Floating There are several factors which are identified as the cause of neutral floating. The impact of Floating Neutral is depend on the position where neutral is broken.

At the 3-Φ Distribution Transformer

  • Neutral failure at transformer is mostly failure of neutral bushing.
  • The use of Line Tap on transformer bushing is identified as the main cause of neutral conductor failure at transformer bushing. The conductor start melting and resulting broke off neutral.
  • Poor workmanship of installations and technical staff also one of the reasons of neutral failure.
  • A broken neutral on 3-Φ transformer will cause the voltage float up to line voltage depending upon the load balancing of the system. This may damage the customer equipment connected to the supply.
  • Some customer will experience overvoltage while some will experience low voltage.  

Broken overhead Neutral conductor in LV line

  • The impact of broken overhead neutral conductor at LV overhead distribution will be similar to the broken at transformer.
  • Supply voltage floating up to Line voltage instead of phase voltage. This type of fault condition may damage customer equipment connected to the supply.

Broken Service Neutral conductor

  • A broken neutral of service conductor will only result of loss of supply at the customer point. Not any damages to customer equipment.

High Earthing Resistance of Neutral at Distribution Transformer

  • Good earthing resistance of earth pit of neutral provide low resistance path for neutral current to drain in earth. High earthing resistance may provide high resistance path for grounding of neutral at distribution transformer.   
  • Limit earth resistance low to permit adequate fault current for operation of protective devices in time and to reduce neutral shifting.

Over Loading and Load unbalancing

  • Distribution network overloading combined with poor load distribution is one of the most reason of neutral failure.
  • Neutral should be properly designed so that minimum current will be flow in to neutral conductor.
  • In overloaded unbalancing network lot of current will flow in neutral which break neutral at its weakest point.

Poor Workmanship and maintenance

  • Normally LV network are mostly not given attention by the maintenance staff. Loose or inadequate tightening of neutral conductor will effect on continuity of neutral which may cause floating of neutral.

How to detect Floating Neutral Condition in Panel Transformer secondary in star connected, then Phase to Neutral = 240V and Phase to phase= 440V.

Condition 1: Neutral is not floating In this condition, the voltage will be same as per the above voltages under balanced condition.

Condition 2: Neutral is floating

All appliances are connected In this condition, it is being fed with a very small current flowing from the phase supply via the plugged-in-appliances to the neutral wire.

All appliances are disconnected In this condition, the neutral will no longer seem to be Live because there is no longer any path from it to the phase supply.

  • Phase to phase voltage: 440C AC
  • Phase to Neutral voltage: 110V to 330V AC
  • Neutral to Ground voltage: 110V
  • Phase to Ground voltage: 120V

Methods of elimination of Neutral Floating There are some point needs to be consider to prevent such situation of neutral floating.

  1. Use 4 Pole Circuit breaker/ELCB/RCBO in distribution panel provides tripping to the circuit without damage to the system.
  2. Use voltage stabilizers with wide input voltage range with high & low cutoff.
  3. Good workmanship and maintenance.

HEALTH EFFECTS OF ELECTRICAL POLLUTION [10]

While the term electrical pollution is not a scientific term, there has been a lot of research and case studies done to understand the connection between electrical pollution and human health. Some are as under:

  • The wire and transformers are not only delivering the juice to run the electrical devices, but are also the carrier of dangerous high frequency currents. The high frequency currents most commonly created by computers and other electronic devices are circulated by various wires and system emitting high frequency currents in homes or office environments. Some of those health problems being attributed to electrical pollution include fibromyalgia, attention deficit disorder, asthma, chronic fatigue syndrome, diabetes, multiple sclerosis and migraine headaches.
  • Reduced blood glucose levels.
  • Improved diabetes.
  • Improved asthma.
  • Improved multiple sclerosis.
  • Higher PH (reduced acidity).       
  • Increased headaches frequencies.
  • Improved teacher & student well-being.      
  • Reduced insomnia.
  • Higher dirty electricity has been correlated with Increased cancer incidence.
  • Experiencing Fatigue.
  • Chills
  • Fever and dry throat on consistent basis.
  • Reduced sleeping.
  • Due to some internal factors such as electronic equipment that distorts 50hz power when the dc power has created ac power. A distorted 50Hz wave is a normal 50Hz current polluted by high frequency voltages and currents.

A filter and a meter have been created to measure and control the electrical pollution, the filters are inexpensive and have proven to be effective in controlling the harmful high frequency currents from entering homes or offices. The Graham-Stetzer [11] (GS) meter and GS filters are the most common tools to measure and reduce electrical pollution. The technology used to create the GS meters and filters is based on electromagnetic theories and power engineering principles. The filters provide a low impedance path for high frequency currents from the hot wire(s) to the neutral wire path bypassing the customer loads. Filter frequency ranges from 4 kHz to 100 kHz provide optimal results for cleaning the electricity. Any frequencies above 100 kHz or below 4 kHz are hard to detect by the filters.

Averaging or RMS meters do measure the amount of electricity present, but the GS meters have demonstrated their ability to measure the amount of harmful electricity present. Electrical current enters the body more readily at higher frequencies, and body current at those higher frequencies can be harmful. The GS meter measures currents at those higher frequencies by measuring the sum of the frequencies above 60 Hz.

CONCLUSION

Electrical pollution, otherwise known as dirty electricity is a term used to describe a type of electrical phenomenon occurring worldwide. However, the phenomenon is not widely known, and can be complex to understand. But research and case studies have shown that consumers should learn about electrical pollution, how it is controlled and measured, the health effects, and public protection against electrical pollution. With this in mind, it is important to understand what causes electrical pollution and what to look for in your everyday environment and home. Many people complain about a variety of side effects to dirty power, these can include headacks, ringing in the ears, trouble focusing, and a variety of other symptoms. If you suffer from some of these symptoms then you may want to discuss this with your doctor. Electrical pollution can be controlled with special filters designed by Graham Stetzer. Graham Stetzer filters (GS filters) can help reduce the harmful electricity that enters home or office environments. The GS filters work best when the utility has an adequate neutral conductor. This means that the conductor can handle more than the standard utility practice to meet thermal or voltage regulation. The above prospective are the major issues responsible for electrical pollution in our environment and can be the solution techniques for implementation.     

References

  1. Magda Havas, “Health concerns associated with Energy efficient lighting and their Electromagnetic emissions”, Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR), June, 2008.
  2. S Durairaj & Revathy Subhiah Rajaram, “E-Waste Recycling-A potential business opportunity in India”, Journal Electrical India, Edition January, 2014.
  3. Mrugen Sheth & Amrita Tondon, “Understanding of Arc Flash Hazard in Power System”, Journal Electrical India, Edition September, 2014.
  4. V V Khatavkar & S N Chapbekar, “Study of Harmonics in Industries- A power quality aspect”, Journal Electrical India, Edition November, 2006.
  5. Sachin K jain & S N Singh, “Estimation of Grid Harmonics in the Modern Electric Power Systems”, Journal Electrical India, Edition July, 2012.
  6. Nagarjun Y, “Lightning and Surge Protection for Motors”, Journal Electrical India, Edition July, 2013.
  7. R. Ramanujam, “An introduction to Power System Stability, Control & Operation”, ISTE-WPLP Learning Material Series, Edition 2014, page no. 75
  8. Jignesh Parmar, “Impact of Floating Neutral in Power Distribution”, Journal Electrical India, Edition February, 2014.
  9. Rabinarayana Parida, Pranati Panigrahi & Bibhu Prasad Nanda, “Flicker meter and its application for Lightning apparatus”, Journal Electrical India, Edition June, 2013.
  10. Report of “The National Foundation for Alternative Medicine”, “The health effects of electrical pollution”, 1629 K Street NW Suite 402, Washington DC, 2006.
  11. Report of “Stetzer Electric”, “Manufacturers of dirty electricity filters and meters”, pp. no. 6-8, www.dirtyelectricity.org, 2005 

Published by PQTBlog

Electrical Engineer

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