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92
Power Quality Analyzer Model 3945-B
Distortion Factor Calculation (DF)
Twoglobalvaluesgivingtherelativequantityofharmonicsarecomputed:theTHD
in proportion to the fundamental and the DF in proportion to the RMS value.
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1
iAthd ,
1
i Uthd,
1
iVthd
50
2
2
50
2
2
50
2
2
iAharm
niAharm
iUharm
niUharm
iVharm
niVharm
nnn
∑∑∑
===
===
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[]
[]
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[]
[]
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[]
iArms
niAharm
iUrms
niUharm
iVrms
niVharm
nnn
∑∑∑
===
===
50
2
2
50
2
2
50
2
2
2
1
iAdf ,
2
1
i Udf,
2
1
iVdf
Multiplying the voltage harmonic factor with the current harmonics factor gives the
power harmonic factor. Differentiating voltage harmonic phase angle with current
harmonic phase angle gives power harmonic phase angle.
VAharm[3][51] , VAph[3][51]
K Factor
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[][ ]
iAkf K factor for the i + 1 phase
n=50
1
2
n
2
n iAharm
n
∑
=
[][ ]
n=50
1
2
niAharm
n
∑
=
=