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App 5-1
IM CW140-E
Explanation of Reactive Power Method
App
Appendix
Appendix 5. Explanation of Reactive
Power Method
Reactive Power Method
The CW140 can calculate reactive power either with or without the reactive
power method (reactive power 1 or 2).
●
Calculation Without Using Reactive Power Method Option (Reactive
Power 2)
The CW140 calculates reactive power from apparent power VA (product of
the effective voltage and current) and active power P using the following
equation.
If the voltage and current have different frequency elements, their effective
values are used for the calculation.
Even if this calculation option is selected, the CW140 makes calculations
based on this method in the background, where the polarity (SQ) determined
by the method is used.
If the current lags behind the voltage: no polarity is indicated
If the current leads the voltage: negative (-) polarity is indicated
Q = SQ (VA)
2
–P
2
SQ = Polarity determined by reactive power method
VA = Apparent power
Q = Reactive power
P
= Active power
With reactive power 2, the power factor, which is also determined by the
apparent power and active power, is called effective power factor. This
calculation method is commonly used. The CW140 uses the polarity
determined by the reactive power method so that it can tell whether the power
factor is leading or lagging.