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Lecture-4 OutlineWhat is Power QualityImproving Power QualityHarmonic AnalysisTotal Harmonic Distortion ( THD)Harmonics in 3-phase SystemsHarmonics in Transformers1What is Power Quality?Definitions of the quality of the supplied voltage (what about the current?)Usually referred in negative contexts power quality problemsMeasurementIEC 61000-4-7 Voltage FlickerIEC 61000-4-15 Harmonic MeasurementIEC 61000-4-30 Measurement Accuracy (Class A, Class S)IEC 62052/3-11, 22, 23 Energy Accuracy (Class 0.2S, Class 0.5S)Power QualityBS:EN 50160:In use worldwide, in favor of the utilities, voltage only,statistical standardIEEE 519 and IEEE 1159: American standards, practical point of viewGOST 13019: Russian standard, very comprehensiveG5/4: British standard for Harmonics (also current)Customized:Allows the user to select the best of all, including faultrecording, waveform capture and more

2Frequency

Voltage Variations

Voltage Flicker

Voltage Dip

Power Quality Parameters3Interruptions

Temporary Overvoltage

Transients

Power Quality Parameters4Unbalance

HarmonicsInterharmonics

Power Quality Parameters5Harmonics+=

IEEE1159-EN50160 LevelsIEEE 1159EN50160No.CategoriesTypical Spectral ContentTypical DurationTypical Voltage MagnitudeShort Duration VariationsInstantaneous7Sag0.5-30 Cycles0.1-0.9 pu