Impact of Non-Linear Loads on Wiring Requirements

1. Impact of Non-Linear Loads on Wiring Requirements Jens Schoene December 06, 2011

2. Who we are • EnerNex is a consulting company with headquarter in Knoxville, TN • Power System Studies • Power Quality • Wind and Solar (design, generator modeling,…) • T&D (bulk system analysis, SSR, CSS) • Safety (arc flash, grounding, electromagnetic coupling) • Smart Grid Engineering Studies • Advanced Metering Infrastructure (AMI) • Utility Communication Architecture • Security

3. Outline • Motivation • Fundamentals of Power Quality • Changing Energy Consumption and Changing Loads • Characteristics of “New” Lighting Technologies • Case Studies • Conclusions and Recommendations

4. Motivation

5. Background • Higher penetration of “new” load types: • Energy-efficient lighting • Consumer electronics • Residential appliances • Plug-in Electric Vehicles • What is the impact? • Wiring requirements • Efficiency, reliability, power quality

6. NEC Wiring Requirement NEC 310.15(B)(5)(c) • No information regarding harmonic limits for which the neutral has to be considered a current carrying conductor • No information regarding required size of neutral conductor in the presence of harmonics • Old buildings have undersized neutral or neutral size equals the size of the phase conductor. • New commercial buildings commonly employ oversized neutral.

7. Fundamentals of Power Quality

8. What are Harmonics? • Harmonics are sinusoidal voltages and currents with frequencies that are integer multiples of the fundamental frequency (60 Hz in the United States). • Value of the multiplier corresponds to the harmonic order.

9. General Effects of Harmonics Harmonics can cause • Transformer overheating resulting in the shortening of the expected lifetime • Capacitor can failure due to excessive harmonic currents or overvoltage stress on dielectrics • Increased ohmic losses and shortened lifetime of cables • Overloaded neutral conductors (odd harmonic currents do not cancel in the neutral conductor) • Nuisance tripping of breakers and fuses • Motor heating • Control misoperation • Communication system interference • Degrade meter accuracy

10. Effects on Wiring Requirements • Measure of heating in conductor is product of squared current I and impedance Z (I2Z) • Harmonics increase heating in conductors due to • additional load current flowing throughconductor • current redistribution inside conductor (skin effect)

11. What is special about 3rd Harmonics? • Add arithmetically in the Neutral (assuming balanced 3-phase system) • Many electronic loads produce them. • Neutral size in commercial building of particular concern.

12. How to Quantify Harmonics • Individual Harmonic Distortion (IHD) LevelPercentage of individual harmonic relative to fundamental • Total Harmonic Distortion (THD) LevelPercentage of RMS of all harmonics relative to fundamental • IEEE 519 specifies limits

13. Changing Energy Consumption andChanging Loads

14. Increasing Electricity Consumption Residential Electricity Consumption in the U.S.A. 1990-2006 source: International Energy Agency, 2009

15. What consumes Electricity? Distribution of USA Electricity Consumption in 2005 source: Energy Information Administration, 2008

16. Changing Electricity Consumption Changes in Electricity Consumption in the USA from 1998 to 2008 source: International Energy Agency, 2009

17. Changing Electricity Consumption Global CE and ICT Electricity Consumption 1990-2030 (Business As Usual) source: International Energy Agency, 2009

18. Changing Electricity Consumption Global CE and ICT Electricity Consumption 1990-2030 (BAU, LLCC, BAT) source: International Energy Agency, 2009

19. Lighting • Lighting is 16% of residential load • Most incandescent lamps phased-out by 2014 • Compact Fluorescent Lamps • Color Rendering Index around 80 • Some are dimmable (most are not) • Some are high power factor / low harmonics (most are not) • White LED • Even more efficient than CFL

20. Characteristics of “New” Lighting Technologies

21. Increased Energy Efficiency

22. How does a CFL work? Electronic Ballast in Energy-Efficient Lighting

23. Harmonic Characteristics Incandescent Compact Fluorescent White LED

24. Case Studies

25. Currents and Voltages Measured at Different Locations (PQube Data) • Comp. 1: Office Building in Knoxville, TN • Comp. 2: Manufacturing Facility in Alameda, CA • Comp. 3: Office Building in Santa Clara, CA • Comp. 4 Manufacturing Facility in Karlsruhe, Germany

26. Phase Currents Industrial Industrial Commercial Commercial Industrial

27. Neutral Currents Industrial Commercial Commercial Industrial

28. Conclusion and Recommendations

29. Conclusions & Recommendations • Electricity consumption and load characteristics changing • 3rd harmonics produced by power electronics are concern • NEC does recognize neutral as current carrying conductor, but no guidance/requirement regarding size. • Neutral sizing requirements should be based on statistically significant data from measurements of neutral currents in different environments (office buildings, residential building, etc.)

30. Backup

31. Power Factor: Displacement vs. True Not all Power Factors are alike

32. Resonances

33. Series Resonance

34. Parallel Resonance