Harmonic detection and filtering - Schneider Electric

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The essential indicatorsof harmonic distortionand measurement principles2.5.4 Relation between power factor and THDWhen the voltage is sinusoidal or virtually sinusoidal, it may be said that:P# P = U . I .cosϕ1 1 1 1Consequently:P U . I .cosϕFP = #S U1.I rms1 1 1Where as:II1rms=11 + THD2IHence:FP#cosϕ 121 + THD IFigure 7 shows a graph of PF / cos ϕ as a function of THDi.PF / cos ϕ = f (THDi ).E55528Figure 7 - Variation of PF / cos ϕ as a function of THDi, where THDu = 0.14
En brefThe primary indicator is the THD, asingle value that reflects the level ofdistortion in voltage and currentwaves.The harmonic spectrum provides a"fingerprint" of the distorted signal.2.6 Usefulness of the various indicatorsb The voltage THD indicates the distortion of the voltage wave.The measured THDu can provide information on phenomena observed in theinstallation. A THDu value of less than 5 % is considered normal and there is virtuallyno risk of equipment malfunctions.A THDu value between 5 % and 8 % indicates significant harmonic distortion. Someequipment malfunctions may occur.A THDu value higher than 8 % indicates high harmonic distortion. Equipmentmalfunctions are probable. In-depth analysis is required and an attenuation systemmust be installed.b The current THD indicates the distortion of the current wave.To identify the load causing the disturbance, the current THD must be measured onthe incomer and the outgoers of the different circuits.The measured THDi can provide information on phenomena observed in theinstallation. A THDi value of less than 10 % is considered normal and there is virtuallyno risk of equipment malfunctions.A THDi value between 10 % and 50 % indicates significant harmonic distortion.Temperature rise may occur, which means cables and sources must be oversized.A THDi value higher than 50 % indicates high harmonic distortion. Equipmentmalfunctions are probable. In-depth analysis is required and an attenuation systemmust be installed.b The power factor PF indicates the extent to which the source of the installationmust be oversized.b The crest factor is used to determine the capacity of a generator (UPS orgenerator) to provide high instantaneous currents. For example, computers drawhighly distorted current with crest factors that may reach 3 or even 5.b The spectrum (signal broken down into frequency) provides a different view ofelectrical signals and may be used to assess distortion.15
Page 1: Low voltage expert guidesHarmonic d
Page 7 and 8: GeneralEn bref1.1 Definition of har
Page 9 and 10: En brefHarmonic currents are caused
Page 11 and 12: 1.2 Why harmonics need to be detect
Page 13 and 14: 2.3 Power and harmonics2.3.1 Active
Page 15: En bref2.5 Total harmonic distorsio
Page 19 and 20: 3.2 Procedure for harmonic analysis
Page 21 and 22: The main effects of harmonicsin ins
Page 23 and 24: 4.2.2 Losses in asynchronous machin
Page 25 and 26: standard UTE C15-112 indicates a de
Page 27 and 28: The graphs in figure 11 below show
Page 29 and 30: 4.5.4 Reduction in the service life
Page 31 and 32: 5.4 Maximum permissible harmonic va
Page 33 and 34: 6.1.3 Separating the sourcesIn effo
Page 35 and 36: En brefIn cases where the preventiv
Page 37 and 38: 6.2.4 Selection criteriab passive f
Page 39 and 40: E95389DB1051547.1.3 Using power-met
Page 41 and 42: Circuit MonitorMicrologic control u
Page 43 and 44: Circuit MonitorMicrologic control u
Page 45 and 46: ION7650 ION7550 ION7350 ION7330 ION
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Page 50 and 51: Harmonic-management solutionsfrom S
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