© 2011 enernex. all rights reserved. impact of non-linear loads on wiring requirements jens...

© 2011 EnerNex. All Rights Reserved. www.enernex.com

Impact of Non-Linear Loads on Wiring Requirements

Jens Schoene

December 06, 2011


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


Outline

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

3


Motivation


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


NEC Wiring RequirementNEC 310.15(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.


Fundamentals of Power Quality


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.


General Effects of HarmonicsHarmonics 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

January 31, 1996 at 18:07:36 LocalX38480VPhase A-B VoltageWave Fault

Trigger

0 20 40 60 80 100-1000

-750

-500

-250

0

250

500

750

1000

Time (mSec onds )

Vo

lts

Max861.3Min-856.4Duration

0.071 Sec

Uncalibrated Data


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)

10


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.


How to Quantify Harmonics

12

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

𝑇𝐻𝐷=√∑𝑖=2

𝑛

𝐻 𝑖2

𝐻1

∙100%

ISC/IL

IHD for Odd Harmonic Currents THD for Odd

Harmonic Currents

h < 11 11 ≤ h < 17 17 ≤ h < 23 23 ≤ h < 35 35 ≤ h

<20 4.0% 2.0% 1.5% 0.6% 0.3% 5.0%20-50 7.0% 3.5% 2.5% 1.0% 0.5% 8.0%

50-100 10.0% 4.5% 4.0% 1.5% 0.7% 12.0%100-1000 12.0% 5.5% 5.0% 2.0% 1.0% 15.0%

>1000 15.0% 7.0% 6.0% 2.5% 1.4% 20.0%


Changing Energy Consumption and

Changing Loads


Increasing Electricity Consumption

14

Residential Electricity Consumption in the U.S.A. 1990-2006

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0

200

400

600

800

1000

1200

1400

1600

1990 1992 1994 1996 1998 2000 2002 2004 2006

Per-

Capi

ta E

lect

rici

ty C

onsu

mpti

on (k

Wh)

Tota

l Ele

ctri

city

Con

sum

ption

(TW

h)

Year

Per-CapitaElectricityConsumptionTotal

ElectricityConsumption

source: International Energy Agency, 2009


What consumes Electricity?

15

Distribution of USA Electricity Consumption in 2005

source: Energy Information Administration, 2008


Changing Electricity Consumption

16

Changes in Electricity Consumption in the USA from 1998 to 2008


-60.00

-40.00

-20.00

0.00

20.00

40.00

60.00

80.00

100.00

120.00

Chan

ge in

Ele

ctri

city

Con

sum

ption

(TW

h)



17

Global CE and ICT Electricity Consumption 1990-2030 (Business As Usual)

0

200

400

600

800

1000

1200

1400

1600

1800

2000

1990 1995 2000 2005 2010 2015 2020 2025 2030

Elec

tric

ity C

onsu

mpti

on (T

Wh)

Year

Miscellaneous

PCs and Monitors

Set-top Boxes

Televisions




18

Global CE and ICT Electricity Consumption 1990-2030 (BAU, LLCC, BAT)


0

200

400

600

800

1000

1200

1400

1600

1800

2000

1990 1995 2000 2005 2010 2015 2020 2025 2030

Elec

tric

ity C

onsu

mpti

on (T

Wh)

Year

Business As Usual (BAU)

Least Life-Cycle Cost (LLCC)

Best Available Technology (BAT)


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


Characteristics of “New” Lighting Technologies


Increased Energy Efficiency

21

0

50

100

150

200

250

0 500 1000 1500 2000 2500 3000 3500 4000 4500

Elec

tric

ity

Cons

umpti

on (

Watt

)

Initial Luminous Flux (Lumen)

Incandescent Light (750 to 4,000 Hours)

Compact-Fluorescent Light (8,000 to 12,000 Hours)

White LED (30,000 to 50,000 Hours)


How does a CFL work?

Electronic Ballast in Energy-Efficient Lighting

22


Harmonic Characteristics

23

Incandescent

CompactFluorescent

White LED


Case Studies


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 Configuration Wye/StarNominal Line-to-Neutral Voltage 120VNominal Line-to-Line Voltage 208VNominal Frequency 60Hz

Transformer Configuration Wye/StarNominal Line-to-Neutral Voltage 277VNominal Line-to-Line Voltage 480VNominal Frequency 60Hz

Power Configuration Wye/StarNominal Line-to-Neutral Voltage 120VNominal Line-to-Line Voltage 208VNominal Frequency 60Hz

Power Configuration Wye/StarNominal Line-to-Neutral Voltage 230VNominal Line-to-Line Voltage 400VNominal Frequency 50Hz


Phase Currents

26

Industrial

Industrial

IndustrialCommercial

Commercial


Neutral Currents

27

Industrial

IndustrialCommercial

Commercial


Conclusion and Recommendations


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.)

29


Backup


Power Factor: Displacement vs. True

31

Not all Power Factors are alikeIm

Re

q

S jQ

P


Resonances

32


Series Resonance

Distribution Substation Bus

CustomerPower FactorCorrection

HighVoltageDistortion

HighHarmonicCurrents

33


Parallel Resonance

Non-LinearLoads

MagnifiedHarmonicCurrents

HighVoltageDistortion

34

© 2011 enernex. all rights reserved. impact of non-linear loads on wiring requirements jens...

Documents

motivation slide

neutral size

meter accuracy slide

z harmonics

phase conductor

rd harmonics

phase system

conductor skin effect