Harmonics in Etap for solar farm

Overview ©1996 2013 ETAPOperation Technology, Inc – Workshop Notes Harmonics Harmonic Analysis Slide 2 ©1996 2013 ETAPOperation Technology, Inc Workshop Notes Harmonics Types of Power Quality Proble.

Harmonic Analysis

Types of Power Quality

Problems

Harmonics

• One special category of power quality

problems

• “Harmonics are voltages and/or currents

present in an electrical system at some

multiple of the fundamental frequency.”

(IEEE Std 399, Brown Book)

1 1

3 2

Harmonic Sources

• Utilities (Power Grid)

– Known as “Background Harmonic”

– Pollution from other irresponsible customers

fractional-Harmonic Sources (cont’d)

• Transformers

– Due to magnetizing branch saturation

– Only at lightly loaded condition

– Usually a current source

• Power Electronic Devices

– Charger, Converter, Inverter, UPS, VFD, SVC, HVDC,

FACTS, … – Due to switching actions

Harmonic Sources (cont’d)

• Other Non-Linear Loads

– Arc furnaces, discharge lighting, …

– Due to unstable and non-linear process

– Either a voltage source or a current source

• In general, any load that is applied to a

power system that requires other than a

sinusoidal current

Harmonic I and V

Phase Angle Relationship

• Fundamental Frequency

Phase Angle Relationship

• Third Order

Phase Angle Relationship

• Fifth Order

• Seventh Order

Order vs Sequence

Characteristic Harmonics

Characteristic Harmonics

(cont’d)

Harmonic Spectrum

Harmonic-Related Problems

• Motors and Generators

– Increased heating due to iron and copper losses – Reduced efficiency and torque

– Higher audible noise

– Cogging or crawling

Harmonic-Related Problems

(cont’d)

• Transformers

– Parasitic heating

– Increased copper, stray flux and iron losses

• Capacitors (var compensators)

– Possibility of system resonance

– Increased heating and voltage stress

Harmonic-Related Problems

(cont’d)

• Power Cables

– Involved in system resonance

– Voltage stress and corona leading to dielectric

failure – Heating and derating

• Neutrals of four-wire systems (480/277V; 120/208V)

– Overheating

Harmonic-Related Problems

(cont’d)

• Switchgears

– Increased heating and losses

– Reduced steady-state current carrying capability – Shortened insulation components life

• Relays

– Possibility of misoperation

• Metering

Parallel Resonance

Capacitor Banks

Capacitor Banks

Capacitor Banks

Say, Seventh Harmonic Current = 5% of 1100A = 55 A

Capacitor Banks

Parallel Resonance (cont’d)

Cause:

Impacts: 1 Excessive capacitor fuse

operation

2 Capacitor failures

3 Incorrect relay tripping

Source inductance resonates with capacitor bank at a frequency

excited by the facilities harmonic

sources

Harmonic Distortion

Measurements

• Total Harmonic Distortion (THD)

– Also known as Harmonic Distortion Factor

(HDF), is the most popular index to measure the level of harmonic distortion to voltage and

current – Ratio of the RMS of all harmonics to the

fundamental component – For an ideal system THD = 0%

Harmonic Distortion

Measurements (cont’d)

1 2

2

F

F THD

Harmonic Distortion

Measurements (cont’d)

• Individual Harmonic Distortion (IHD)

- Ratio of a given harmonic to fundamental

- To track magnitude of individual harmonic

1

F

F

• Root Mean Square (RMS) - Total

- Root Mean Square of fundamental plus all harmonics

- Equal to fundamental RMS if Harmonics are

Reducing System

Harmonics

• Add Passive Filters

– Shunt or Single Tuned Filters – Broadband Filters or Band Pass Filters – Provide low impedance path for harmonic

current – Least expensive

Reducing System

Harmonics (cont’d)

• Increase Pulse Numbers

– Increasing pulse number of convert circuits

– Limited by practical control problems

Reducing System

Harmonics (cont’d)

• Apply Transformer Phase Shifting

– Using Phase Shifting Transformers

– Achieve higher pulse operation of the total

converter installation

• In ETAP

– Phase shift is specified in the tab page of the

transformer editor

Reducing System

Harmonics (cont’d)

• Either standard phase shift or special phase shift can be used

Reducing System

Harmonics (cont’d)

• Add Active Filters

– Instantly adapts to changing source and load

conditions – Costly

– MVA Limitation

Voltage Distortion Limits

Recommended Practices for Utilities (IEEE

At PCC

Individual Distortion (%)

Total Voltage Distortion THD (%)

In ETAP:

Specify Harmonic Distortion Limits in Harmonic

Page of Bus Editor:

Current Distortion Limits

Recommended Practices for General

Distribution Systems (IEEE 519):