power system harmonics 2

8/14/2019 Power System Harmonics 2

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POWER SYSTEMPOWER SYSTEM

HARMONICSHARMONICS

GOURI SHANKARGOURI SHANKARDALABEHERADALABEHERA


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What is Harmonics?What is Harmonics?

Harmonics are defined as the sinusoidal components of aHarmonics are defined as the sinusoidal components of a

non-linear periodic waveform with a frequency that is anon-linear periodic waveform with a frequency that is awhole multiple of the fundamental frequency.whole multiple of the fundamental frequency.the term total harmonic distortion (THD). expresses thethe term total harmonic distortion (THD). expresses the

distortion as a percentage of the fundamental (pure sine)distortion as a percentage of the fundamental (pure sine)of voltage and current waveforms.of voltage and current waveforms.


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Figure-1Figure-1


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Figure-2Figure-2


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Figure-3Figure-3


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Sources of HarmonicsSources of Harmonics

Transformers under no loads andTransformers under no loads andlight loads.light loads.

Rotating machines.Rotating machines.Rectifiers.Rectifiers.Industrial drives.Industrial drives.

Electrolysis plantsElectrolysis plants


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How Harmonics AreHow Harmonics AreProducedProduced ??

Non-linear loads create harmonics by drawing currentNon-linear loads create harmonics by drawing currentin abrupt short pulses, rather than in a smoothin abrupt short pulses, rather than in a smoothsinusoidal mannersinusoidal mannerThey occur frequentlyThey occur frequently

When there are large numbers of personal computersWhen there are large numbers of personal computers(single phase loads), uninterruptible(single phase loads), uninterruptiblepower supplies (UPSs), variable frequency drives (ACpower supplies (UPSs), variable frequency drives (ACand DC) or any electronicand DC) or any electronicdevice using solid state power switching supplies todevice using solid state power switching supplies toconvert incoming AC to DC.convert incoming AC to DC.


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How do harmonics affect us? How do harmonics affect us?

Greater risk of interference withGreater risk of interference withcommunication network.communication network.

High currents in neutrals due toHigh currents in neutrals due toTriplentsTriplentsOverheating due to overloading of Overheating due to overloading of capacitors, motors, transformers,capacitors, motors, transformers,cablescables


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How Variable Frequency DrivesHow Variable Frequency DrivesCause HarmonicsCause Harmonics


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Harmonics Analysis:Harmonics Analysis: Power factor correction capacitorsPower factor correction capacitors

are protected from short circuits as aare protected from short circuits as aresult of occurrence of parallelresult of occurrence of parallelresonance by using de-tuned filters.resonance by using de-tuned filters.

Tuned filters are used to suppressTuned filters are used to suppressindividual harmonic orders.individual harmonic orders.


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Capacitor Voltage and CurrentCapacitor Voltage and CurrentRelationshipsRelationships


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Effects and NegativeEffects and NegativeConsequencesConsequences

Harmonics can lead to power systemHarmonics can lead to power systeminefficiency. Some of the negative waysinefficiency. Some of the negative waysConductor Overheating:Conductor Overheating:Capacitors:Capacitors:Fuses and Circuit Breakers:Fuses and Circuit Breakers:Transformers:Transformers:

Utility Meters:Utility Meters:


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Reducing HarmonicsReducing Harmonics

12-pulse converter front end:12-pulse converter front end:

Typical Twelve-Pulse Front End Converter for AC Drive


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Delta-Delta and Delta- WyeDelta-Delta and Delta- WyeTransformers:Transformers:Isolation TransformersIsolation TransformersLine Reactors:Line Reactors:


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ConclusionConclusion

identifying the size and location of non-identifying the size and location of non-linear loads should be an important part of linear loads should be an important part of any maintenance, troubleshooting and repairany maintenance, troubleshooting and repairprogram.program.Observe various methods as possible as toObserve various methods as possible as toreduce harmonicsreduce harmonicsThis article was intended to provide anThis article was intended to provide anintroduction to the basic principles of powerintroduction to the basic principles of powersystem harmonics.system harmonics.


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THANK UTHANK U

power system harmonics 2

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