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Power Quality Products and Applications

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Harmonic BasicsHarmonic Basics Harmonics is a term used to explain currents

and voltages that have multiplied in an AC electrical power network

Harmonic producing areas include ferromagnetics (transformers, motors), arcing equipment (welders, arc furnaces), and rectifiers (UPS, adjustable speed drives)

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Harmonic BasicsHarmonic Basics Power electronic devices

used in numerous equipment

Loads are non-linear, with an erratically shaped sine-wave

60hz fundamental becomes amplified when harmonics present

5th order harmonic represents 300hz

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Harmonic BasicsHarmonic Basics Harmonic spectrum may include various

harmonic orders, each with its own values for current and voltage

IEEE 519 Guide for Harmonics, references different types of harmonics and methods for mitigation

Industrial applications typically involve odd order harmonics, 5th, 7th, 11th, 13th

Zero sequence harmonics affect the neutral

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Harmonics BasicsHarmonics BasicsCommon Causes

Adjustable speed drives and systems, electric arc furnaces, welding equipment, transformers and generators, UPS and storage systems, medical/dental equipment, lighting controls/dimmers, computers, copiers, scanners

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Harmonic BasicsHarmonic BasicsEffects of Harmonics

Overheating of conductors, bus bar, switchgear, circuit breaker nuisance tripping/arcing, meters/instruments not accurate, AC motor reverse torque, transformers overheating/insulation breakdown, capacitors overload/blown fuse, reduced equipment life, early failure

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Harmonics BasicsHarmonics BasicsHarmonics and PFC

Capacitors do not create harmonics Concern for resonance – currents

amplified, voltage distortion, potential damage to capacitors

Reactors help to “de-tune” to below a certain order, balancing the capacitive requirement

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Harmonics Application ReviewHarmonics Application Review Facility walk-through – installed

equipment, systems and processes Review plant electrical documents Note plans for new equipment,

expansion Analyze 6-12 months of electric bills Review past electrical system studies,

may require a PQ survey, energy audit

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Harmonics Application ReviewHarmonics Application Review Note equipment most vulnerable to

harmonics Any critical loads and process requiring

“premium power”, outage concerns? Review downtime, scrap, maintenance,

equipment replacement costs, loss of production, profits

Isolated solution, long term PQ strategy

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Harmonic BasicsHarmonic BasicsWhere Harmonics Exist

Water treatment, glass making, steel processing, packaging, data centers, printing/publishing, paper processing, plastics, chemicals, automotive, to name few

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Harmonic BasicsHarmonic BasicsEconomic Considerations

Harmonics can create nuisance problems (rebooting a PC, restarting equipment) to serious concerns (product quality issues), through catastrophic events (production halted)…….monies lost

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Harmonic BasicsHarmonic Basics New and replacement

equipment/controls and devices typically are electronic, which may exacerbate a border-line harmonic condition, immediately creating a new set of problems, which ultimately affect business…….monies lost

Partial “fixes”, lack to review total PQ situation……..monies lost

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Harmonic BasicsHarmonic BasicsSuggestions

Keep a record of problems and associated costs

Actions taken to review and “fix” problem(s), associated costs

Potential need to monitor (collect data) on facility loads, to help with evaluation

Discuss problem with a “solutions driven” equipment manufacturer

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IEEE519-1992IEEE519-1992

SCR=IS/IL

Harmonic Percentage

H<11 11-16 17-22 23-24 34<h THD

<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 12.0100-1000 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

Current Distortion Limits for General Distribution Systems (120V through 69000V)

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EN61000-3-4EN61000-3-4Harmonic Number

n

Admissible Harmonic

Current In/Iact (%)

Harmonic Number

n

Admissible Harmonic

Current In/Iact (%)

3 19 21 <0.65 9.5 23 0.97 6.5 25 0.89 3.8 27 <0.611 3.1 29 0.713 2.0 31 0.715 0.7 <33 <0.6

17 1.219 1.1 Even <4/n or <0.6

Admissible Current for Entire Installation

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Conventional Methods to Conventional Methods to Solve HarmonicsSolve Harmonics

Poly-phase Rectifier and Phase-shift Transformer Adding transformers,

thyristors and controller… etc.

Regardless of Mains Power Impedance and Frequency

Must be built-in before equipment delivery

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Conventional Methods to Conventional Methods to Solve HarmonicsSolve Harmonics

Passive Power Filter Made of Capacitors

and Inductors Very Sensitive to

Mains Power Impedance and Frequency

Can be Built-In at Any Time

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Best Method to Solve Best Method to Solve HarmonicsHarmonics

Active Power Filter Uses Solid State

Power Converters Independent of

Mains Power Impedance and Frequency

Can be Built-In Any Time

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Operation Principle of Operation Principle of StacoSineStacoSine

Ih waveform

IeIh

IS

Phase 1: Measure the harmonic current from the load.

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Operation Principle of Operation Principle of StacoSineStacoSine

Ie waveform

IeIh

IS

Phase 2: Inject harmonic current in opposite phase to the load.