Power Quality Analyzer Model 3945
83
8.1.9 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
i
Athd
,
1
i
Uthd
,
1
i
Vthd
50
2
2
50
2
2
50
2
2
i
Aharm
n
i
Aharm
i
Uharm
n
i
Uharm
i
Vharm
n
i
Vharm
n
n
n
∑
∑
∑
=
=
=
=
=
=
[]
[][ ]
[]
[]
[][ ]
[]
[]
[][ ]
[]
i
Arms
n
i
Aharm
i
Urms
n
i
Uharm
i
Vrms
n
i
Vharm
n
n
n
∑
∑
∑
=
=
=
=
=
=
50
2
2
50
2
2
50
2
2
2
1
i
Adf
,
2
1
i
Udf
,
2
1
i
Vdf
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]
8.1.10 K Factor
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[][ ]
i
Akf
K factor for the i + 1 phase
n=50
1
2
n
2
n
i
Aharm
n
∑
=
[][ ]
n=50
1
2
n
i
Aharm
n
∑
=
=
8.1.11 Different Power Levels 1 sec
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[][ ]
i
W
VA[
i
] = Vrms[
i
] Arms[
i
] Apparent power i + 1 phase
VAR[
i
] =
ou VAR[
i
] = VA[
i
] – W[
i
] if computation method is with harmonics
Active power i + 1 phase
NSS-1
0
n
V i
n
.
.
.
∑
=
[][ ]
n
A i
=
1
NSS
[][
]
Reactive power i + 1 phase
NSS-1
0
n - NSS /
4
VF i
n
.
∑
=
[][ ]
n
AF i
1
NSS
2
2
