IEEE519 SAYSIEEE519 SAYSIEEE 519 1992 defines a harmonic as,

"A sinusoidal component of a periodic

wave or quantity having a frequency

that is an integral multiple of the

fundamental frequency.”

Harmonics are a function of the

distribution system and the circuit

configuration of the distorting load.

Definition of HarmonicsDefinition of Harmonics

• They are AC currents or voltages at integer multiples of the fundamental frequency

• The fundamental is the lowest frequency in the waveform, generally the repetition frequency

• They cannot transfer power on the average• Harmonics are present in any non-sinusoidal

waveform• More rapid changes in the waveform require the

presence of higher order harmonics

Harmonics -- The Main Power Quality Issue for VFD’s

Harmonics -- The Main Power Quality Issue for VFD’s

• Where do they come from?• What are Harmonics?• What are the effects of Harmonics? • What are the current standards?• How do you measure Harmonics?• How do you know if there’s a harmonic problem?• How can they be controlled or eliminated?• Common myths and misconceptions• References

Sources of HarmonicsSources of Harmonics

• They arise from non-linear loads in which current is not strictly proportional to voltage

• Linear loads like resistors, capacitors and inductors do not produce harmonics

• Since diodes and SCR’s are non-linear, those circuits generate harmonic currents

• Other equipment which causes harmonics:

– UPS, rectifiers, transformers, ballasts, welders, arc furnaces, and personal computers

Harmonic NoteHarmonic Note

It is important to remember that harmonic

phenomena are "periodic" which indicates

their continuous nature.

It is the continuous phenomena that is

addressed in the IEEE guidelines.

Harmonic StandardsHarmonic Standards• IEEE-519 1992• Definitions:

– Voltage total harmonic distortion (VTHD)– Current total harmonic distortion (CTHD)

• K-Factor• Point of Common Coupling• VTHD Limits, Table 10.2• CTHD Limits, Table 10.3

– Dilution by linear loads• There are no Susceptibility Limits!

THD Definitions from IEEE-519THD Definitions from IEEE-519

Voltage Total Harmonic Distortion VTHD

Current Total Harmonic Distortion CTHD

Sum of squares of amplitudes of all voltage harmonics

Sum of squares of amplitudes of all current harmonics

Amplitude of fundamental voltage

Amplitude of fundamental Current

IEEE519 Tables 10.2/3IEEE519 Tables 10.2/3

Point of Common CouplingPoint of Common Coupling

• The point of common coupling is the location in

the power distribution system where harmonic

distortion is to be measured, usually where

harmonic currents flow into a bus which feeds

other equipment. Its location must be specified!

• In the absence of a specified location, the POCC

for current harmonics is the plant-utility interface

PCC ExamplePCC Example

The Three Phase Diode RectifierThe Three Phase Diode Rectifier

• The three phase equivalent of the diode rectifier.

Three phase diode rectifier, line voltage/current

-700-600-500-400-300-200-100

0100200300400500600700

Voltage Current

Model of Components in Non-Linear Three Phase Circuit

Figure 11.1

Figure 11.2

Generation of Harmonic Currents

Generation of Harmonic Currents

PWM Power ConversionPWM Power Conversion

IEEE519 CommentIEEE519 Comment

IEEE 519 1992IEEE 519 1992

DON’T SAY IT UNLESS YOU MEAN IT

Harmonics are Site Specific and Dependant Upon:

Harmonics are Site Specific and Dependant Upon:

• Distribution transformer’s short circuit capacity

• Distribution transformer’s impedance

• Maximum demand load

a. Linear load

b. Non-linear load

• Location of the PCC

ThereforeThereforeTo Properly Specify IEEE 519 1992 the following

information must be known:

Examples VoltageExamples Voltage

Examples CurrentExamples Current

Ways to Decrease HarmonicsWays to Decrease HarmonicsWays to Decrease Harmonics

• Load Segregation

• Input Line Reactor

• 5th Harmonic Filter

• Active Filter

• 12- Pulse Drive

• 18- Pulse Drive

Helpful FormulasHelpful Formulas• From IEEE Std. 141-1993: Power is the product of in-

phase current times the voltage or:

• P60 = V60 * I60cos θ

• In the case of harmonics:

• Ph = Vh * Ihcos θ or S = (Sqrt(P2 + Q2 +D2)){R1]

• Where P = Real Power, Q = Reactive Power and D = Distortion Power.

• System losses will be higher due to the harmonic components, than with equivalent 60 kVA.

• Ph = I2h * Rh

• (Ohm’s law in harmonic-land)

True Power Factor Representation - Expanded

Appa

rent P

ower

(kVA)

*

P Real Power (kW)Q

Rea

ctiv

ePo

wer

X

(kVA

r)D D

istortio

n

Figure 20.1

Helpful FormulasHelpful Formulas

• Current flowing through system impedances (transformers, wire, inductors) create voltage drops at frequency. Therefore, when non-linear loads draw harmonic frequencies, drops at harmonic frequencies add to create voltage distortion.

E = IR

EDC = IDC R

E60 = I60 (R+jXL60)

E300 = I300 (R+jXL300)

jXL = 2πfL

Harmonic Currents Creating Voltage Distortion

Figure 21.2

SUMMARYSUMMARY• The most important thing to remember is that in order to

utilize the rules of IEEE519 is the full understanding of your power system and equipment.

• The best way to understand your system is to perform a system analysis using the guidelines of IEEE519 or have a outside consultant do a analysis of your power system.

• They are several companies that promote special harmonic filters, traps and guards.

Reference informationReference information• Many thanks to all the people / companies that have written

articles pertaining to this subject.

– IEEE519-1992– TCI– Mirus

• Please contact us with any questions or if you would like to have a power analysis performed at your plant.