Accura 2300/2350 User Guide
Chapter 5 Measurement Description
ⓒ
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Page 199
Phase Power Measurement
Two methods are available for calculating reactive power(Q) and apparent power(S) for each phase.
1) Fundamental calculation: calculation of reactive power based on fundamental voltage/current.
2) Harmonic calculation: calculation of reactive power based on RMS voltage/current
Depending on how the reactive power is calculated, reactive power and apparent power can vary. As the
apparent power varies, the power factor(PF) also varies.
Fundamental Calculation Method
Active power for each phase is calculated by multiplying voltage and current.
𝑃
𝑘
=
1
𝑇
∫ 𝑣
𝑘
(𝑡)
𝑇
0
𝑖
𝑘
(𝑡)𝑑𝑡
where k=a,b,c
,
The reactive power for each phase is calculated by delaying the phase of the voltage by 90 degrees with
respect to the fundamental frequency.
𝑄
𝑘
=
1
𝑇
∫ 𝑣
𝑘
(𝑡 −
𝑇
4
)
𝑇
0
𝑖
𝑘
(𝑡)𝑑𝑡
where k=a,b,c
,
The apparent power for each phase is calculated by the magnitude of the vector sum of the active power and
the reactive power.
𝑆
𝑘
= √𝑃
𝑘
2
+ 𝑄
𝑘
2
where k=a,b,c
,
Harmonic Calculation Method
Active power for each phase is calculated by multiplying voltage and current.
𝑃
𝑘
=
1
𝑇
∫ 𝑣
𝑘
(𝑡)
𝑇
0
𝑖
𝑘
(𝑡)𝑑𝑡
where k=a,b,c
,
Calculate the apparent power for each phase by multiplying the RMS voltage by the RMS current. The RMS
values of voltage and current contain harmonic components.
𝑉
𝑘,𝑟𝑚𝑠
= √
1
𝑇
∫ 𝑣
𝑘
2
(𝑡)
𝑇
0
𝑑𝑡 ,
𝐼
𝑘,𝑟𝑚𝑠
= √
1
𝑇
∫ 𝑖
𝑘
2
(𝑡)
𝑇
0
𝑑𝑡
where k=a,b,c
𝑆
𝑘
= 𝑉
𝑘,𝑟𝑚𝑠
∙ 𝐼
𝑘,𝑟𝑚𝑠
where k=a,b,c
The magnitude of the vector difference between the apparent power and the active power is calculated to
obtaine the magnitude of the reactive power for each phase. The sign of the reactive power is the sign of the
reactive power calculated by the fundamental calculation method mentioned above.
𝑄
𝑘
= ±√𝑆
𝑘
2
− 𝑃
𝑘
2
where k=a,b,c
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