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Operation
Methods of Measurement/Formulas 3
3-17
where
i
P Real power of harmonic order i
i
Q Reactive power of harmonic order i
For historic reasons the cos φ parameter is also included in the V-I-P parameter group:
Calculation formula:
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
=
P
Q
h
arctancoscos
ϕ
where
P Real power
h
Q Harmonic reactive power
Note
If you want to display the displacement power factor of the fundamental
component select the harmonics analysis parameter group and choose the
fundamental component in the drop-down list of available parameters.
Half and full cycle aggregations
Real power
Real power
P
is calculated by directly multiplying the samples of voltage and current in
the time domain.
n
iiiu
P
n
i
∑
=
⋅
=
1
)()(
where
)(iu the i-th voltage sample of the cycle or half cycle
)(ii the i-th current sample of the cycle or half cycle
n
the number of samples per cycle or half cycle
Note
There is no integer number of samples per cycle or half cycle (neither for
50 Hz nor for 60 Hz systems). A 50 Hz cycle consists of 204.8 samples a 60
Hz cycle of 170.67 samples. Therefore the calculation uses sample
interpolation.
The 3-phase real power sum is calculated as
321 LLLsum
PPPP ++=
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