Power Quality & Quality of Supply A Global Continuously Developing Engineering Challenge

Published by Terry Chandler, A Power Quality Practitioner ™ for +30 years,

Director of Engineering Power Quality Thailand LTD/Power Quality Inc. USA,

Consultant for Dranetz Corporation USA (Asia business Unit General Manager)

Contact TerryC@powerquality.org

What is Power Quality (PQ)?

  • The characteristics of the supply voltage and the electrical system that affect the performance of the load.
  • The characteristics of the load that affect the electrical supply system and/or other loads. (TerryC. 1992)

What is Quality of Supply (QOS)?

  • The characteristics of the supply voltage that affect the performance of the load.
  • The characteristics of the electrical distribution system that affects the electrical loads. (Transformer size and distance to the loads)

Power Quality Definition?

  • There are many more definitions from IEC, IEEE, Various PQ engineers and experts.
  • PQ is a complex engineering & economic situation that is constantly changing due to technology and political environment changes. (TerryC. 2006)

PQ problems (costs) vs Power passing thru a semiconductor switch


Semiconductor Sales vs PQ


Power Reliability vs Power Quality

  • Power Reliability is the presence of voltage at the meter point.
  • Power Quality is the value of the voltage (and other PQ parameters) as a percent of nominal at the meter. – Mr. Phil Sarikas, Intel Corporation 4/97

Quality of Supply Parameters (Utility)

  • RMS voltage, Sags (dips) and Surges (swells) – Disturbances
  • Voltage transients (slow, medium, and fast)
    • Lightning and switching transients that damage sensitive electronic loads
  • Sinewave – wave shape-harmonics – System losses
  • Voltage imbalance – phase differences – System losses
  • Flicker- small periodic voltage variations at frequencies lower than ½ fundamental-The only parameter that affects people directly
  • Frequency Variations
  • Power Factor? System losses

Source of most common voltage sag from utility distribution system or transmission or generation


A fault on transmission system


Voltage Sag Example (QOS)


Power Quality Parameters User Side

  • RMS voltage, Sag (dips) and surges (swells)
  • Voltages transients (slow, fast, and extremely fast)
  • Sinewave – wave shape – harmonics (Voltage and current)
  • Voltage imbalance (phase imbalance) (Voltage and current)
  • Flicker- small periodic voltage variations at frequencies lower than ½ fundamental. (current)
    • The only parameter that affects people directly
  • Internal electrical system design and construction.
  • Grounding /Earthing internal. (Ground loops and current in the ground conductor.
  • Waveshapes, Harmonics, Interharmonics (current)

Source of the PQ issues?

In PQI’s 30 years of experience and data shows:

  • 80% of the PQ issues are on the customer side of the meter.
  • 80% of the $ losses are caused by the 20% of the PQ issues from the utility side of the meter.
  • Majority of the issues from utility are voltage sags/short outages, flicker and harmonics caused by other loads.
  • Voltage transients include decaying ringwaves (PF cap switching)
  • Flicker usually caused by steel mill loads but now maybe from wind turbines

Power Quality is a constantly changing situation of varying loads, varying generation types, varying weather.

  • For the first 20 years it was the loads changing in sensitivity to normal electrical distribution operations.
  • Loads changing from incandescent lamps and motors to new technologies and Invertor (VFD,VSD’s) motor drives
  • Generation changing from rotary to invertor-based renewables.
  • Remote generation
  • Harmonics causing losses
  • Government influence/mandates of SmartGrid

Influence on Power Quality due to drive for more energy efficient loads.

  • Lighting technology
    • Incandescent bulbs to Compact Fluorescent to LED
  • Motor Control technology
    • Voltage control to SCR control to High Power Switching
  • Power Switching technology for heating

Today Power Quality is more about data/information. (SmartGrid)

  • SmartGrid ( 7,250,000 results from a Google search)
  • A SmartGrid is an electrical grid which includes a variety of operational and energy measures including smart meters, smart appliances, renewable energy resources, and energy efficiency resources.
  • What does Power Quality have to do with SmartGrid?

Data Integrated by Power Quality Monitoring System at Con Edison

  • Transmission Feeders
    • Digital Fault Recorders
  • Area Substation Transformers
    • Power Quality Monitors
    • Event Correlation with SCADA Breaker Operations
  • Network Distribution Feeders
    • Digital Relays
    • Event Correlation with SCADA Breaker Operations
  • Area Substation Capacitors
    • Indirect: PQ Monitors
    • Direct: Some Digital Relays
  • Secondary Networks
    • Power Quality Monitors
  • Unit Substation Transformers
    • Power Quality Monitoring
    • Phasor Measurement Sensors during Network Intermesh
    • Station Battery Sensors
  • Long Island City Smart Meters
    • Energy and Power Quality Data Logs
  • High Tension Remote Monitoring
    • Power and power quality monitoring
  • Distribution and Transmission SCADA
    • Automatic momentary interruption analysis and correction with IEDs


Energy Efficiency and Power Quality

  • There is a worldwide movement to increase the energy efficiency of loads.
  • According to the International Energy Association, electric motors consume 45 percent of the total energy in the world. Lighting energy consumption is a distant second at 19 percent. https://www.iea.org/
  • Energy efficiency is the one energy resource all countries possess in abundance.

Global Impact of Energy Efficiency


Electrical Energy Efficiency

  • Same amount of work in the same amount of time with less Kilowatts. (KWhr)

Load Categories

  • Industrial
    • Motors, lighting, building envelope, electronics
  • Commercial
    • Lighting, building envelope, electronics
  • Consumer
    • Appliances, lighting, building envelope
  • Government

Parameters of Electrical Usage

  • Voltage stability
  • Voltage imbalance
  • Amps to determine load characteristics
  • Watts, KW, KWhr
  • Power Factor
  • Maximum demand
  • Time of day usage
  • Economic losses and return on investment require data $$$$$

The Basics of Energy Savings

  • Motors
    • VFD/VSD reduce the energy not needed once the load is started
    • Improve the control by electronic switching
  • Lighting
    • Change in technologies
      • Incandescent – Fluorescent – LED – specialty
  • Electronic loads
    • Increased integration of semiconductors
  • Temperature
    • Insulation, control, and technology

The Relationship Electricity usage to Power Quality Situations (parameters)

  • As energy efficiency of loads increases (decreases), it changes the sensitivity to PQ parameters and increases (decreases) the generation of harmonics


Computer Power Supplies (AC to DC)

  • Linear power supplies change to Switch mode.
    • Voltage operating range went from +/- 5% to universal voltage 90vac to 240vac
    • More sensitive to transients
    • Generate more harmonics
  • Next generation
    • PF corrected
    • Lower Ithd but at higher order harmonics


Lighting (22%)

  • Incandescent lights to solid state ballast fluorescent lights
    • Sensitivity to voltage reduced
    • Increase in harmonics
  • Next, LED lights
    • Decrease in harmonics
    • Decrease sensitivity to Voltage?



Lamp Efficiency Comparison and PQ Sensitivity

Light Dimmers

  • Lowers power used
  • Increases Harmonics
  • Sensitive to voltage transients
  • Sensitive to voltage sags
    • Light blinks

Solid State Lights (SSL)

  • Significant energy savings
  • Sensitive to voltage transients
  • AC to DC converter generates harmonics



  • 70% of electrical load (Industrial) 45% of global load
  • High Efficiency motors
  • Electronic controls for existing motors
    • Variable Speed Drives (VFD)
    • Variable Frequency Drives (VSD)
    • Soft start

High Efficiency Motors


Add VFD (VSD) to Motors

  • Variable speed drives
    • Sensitive
      • Sags
      • Phase shifts
      • Transients
      • Imbalance
  • Generates harmonics

How a VFD or VSD works?


Drivers for Change in PQ and Efficiency

  • Cost savings
  • Improving control over processes
  • Energy efficiency (Green World)
  • Reduce size and weight of equipment by lowering power consumption
  • Advances in technology
    • Semiconductor
    • Materials of all types
      • Insulation and conductors


  • Power Quality and Energy efficiency are linked by the changing technologies
  • The Changing technologies are a global situation.
    • The only constant is the varying rate of change!
  • Effective engineering depends on global information and technical resources
  • I have been an IEEE member for more than 30 years! It is a global organization that has provides consistent and valuable resource data for wide variety of electrical subjects

Albert Einstein Quotes

Published by PQBlog

Electrical Engineer

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