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© 2011 EnerNex. All Rights Reserved. www.enernex.com Impact of Non-Linear Loads on Wiring Requirements Jens Schoene December 06, 2011.

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Presentation on theme: "© 2011 EnerNex. All Rights Reserved. www.enernex.com Impact of Non-Linear Loads on Wiring Requirements Jens Schoene December 06, 2011."— Presentation transcript:

1 © 2011 EnerNex. All Rights Reserved. Impact of Non-Linear Loads on Wiring Requirements Jens Schoene December 06, 2011

2 © 2011 EnerNex. All Rights Reserved. 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 2

3 © 2011 EnerNex. All Rights Reserved. Outline Motivation Fundamentals of Power Quality Changing Energy Consumption and Changing Loads Characteristics of New Lighting Technologies Case Studies Conclusions and Recommendations 3

4 © 2011 EnerNex. All Rights Reserved. Motivation

5 © 2011 EnerNex. All Rights Reserved. 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 © 2011 EnerNex. All Rights Reserved. NEC Wiring Requirement NEC (B)(5)(c) 6 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 © 2011 EnerNex. All Rights Reserved. Fundamentals of Power Quality

8 © 2011 EnerNex. All Rights Reserved. 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 © 2011 EnerNex. All Rights Reserved. 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 © 2011 EnerNex. All Rights Reserved. Effects on Wiring Requirements Measure of heating in conductor is product of squared current I and impedance Z (I 2 Z) Harmonics increase heating in conductors due to – additional load current flowing throughconductor – current redistribution inside conductor (skin effect) 10

11 © 2011 EnerNex. All Rights Reserved. What is special about 3 rd 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 © 2011 EnerNex. All Rights Reserved. How to Quantify Harmonics 12 Individual Harmonic Distortion (IHD) Level Percentage of individual harmonic relative to fundamental Total Harmonic Distortion (THD) Level Percentage of RMS of all harmonics relative to fundamental IEEE 519 specifies limits I SC /I L IHD for Odd Harmonic CurrentsTHD for Odd Harmonic Currents h < 1111 h < 1717 h < 2323 h < 3535 h <204.0%2.0%1.5%0.6%0.3%5.0% %3.5%2.5%1.0%0.5%8.0% %4.5%4.0%1.5%0.7%12.0% %5.5%5.0%2.0%1.0%15.0% > %7.0%6.0%2.5%1.4%20.0%

13 © 2011 EnerNex. All Rights Reserved. Changing Energy Consumption and Changing Loads

14 © 2011 EnerNex. All Rights Reserved. Increasing Electricity Consumption 14 Residential Electricity Consumption in the U.S.A source: International Energy Agency, 2009

15 © 2011 EnerNex. All Rights Reserved. What consumes Electricity? 15 Distribution of USA Electricity Consumption in 2005 source: Energy Information Administration, 2008

16 © 2011 EnerNex. All Rights Reserved. Changing Electricity Consumption 16 Changes in Electricity Consumption in the USA from 1998 to 2008 source: International Energy Agency, 2009

17 © 2011 EnerNex. All Rights Reserved. Changing Electricity Consumption 17 Global CE and ICT Electricity Consumption (Business As Usual) source: International Energy Agency, 2009

18 © 2011 EnerNex. All Rights Reserved. Changing Electricity Consumption 18 Global CE and ICT Electricity Consumption ( BAU, LLCC, BAT ) source: International Energy Agency, 2009

19 © 2011 EnerNex. All Rights Reserved. Lighting 19 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 © 2011 EnerNex. All Rights Reserved. Characteristics of New Lighting Technologies

21 © 2011 EnerNex. All Rights Reserved. Increased Energy Efficiency 21

22 © 2011 EnerNex. All Rights Reserved. How does a CFL work? Electronic Ballast in Energy-Efficient Lighting 22

23 © 2011 EnerNex. All Rights Reserved. Harmonic Characteristics 23 Incandescent Compact Fluorescent White LED

24 © 2011 EnerNex. All Rights Reserved. Case Studies

25 © 2011 EnerNex. All Rights Reserved. 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 25 Transformer ConfigurationWye/Star Nominal Line-to-Neutral Voltage120V Nominal Line-to-Line Voltage208V Nominal Frequency60Hz Transformer ConfigurationWye/Star Nominal Line-to-Neutral Voltage277V Nominal Line-to-Line Voltage480V Nominal Frequency60Hz Power ConfigurationWye/Star Nominal Line-to-Neutral Voltage120V Nominal Line-to-Line Voltage208V Nominal Frequency60Hz Power ConfigurationWye/Star Nominal Line-to-Neutral Voltage230V Nominal Line-to-Line Voltage400V Nominal Frequency50Hz

26 © 2011 EnerNex. All Rights Reserved. Phase Currents 26 Industrial Industrial Industrial Commercial Commercial

27 © 2011 EnerNex. All Rights Reserved. Neutral Currents 27 Industrial Industrial Commercial Commercial

28 © 2011 EnerNex. All Rights Reserved. Conclusion and Recommendations

29 © 2011 EnerNex. All Rights Reserved. Conclusions & Recommendations Electricity consumption and load characteristics changing 3 rd 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.) 29

30 © 2011 EnerNex. All Rights Reserved. Backup

31 © 2011 EnerNex. All Rights Reserved. Power Factor: Displacement vs. True 31 Not all Power Factors are alike

32 © 2011 EnerNex. All Rights Reserved. Resonances 32

33 © 2011 EnerNex. All Rights Reserved. Series Resonance 33

34 © 2011 EnerNex. All Rights Reserved. Parallel Resonance 34


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