Measurement of power on the system backflow Janis power can be divided into three, namely
– Apparent power (S) measured in VA or kVA
– Active Power (P) which is measured in watts or kW
– Reactive Power (Q) measured in VAR or kVAR
The relationship between the three power can be explained easily by the power triangle, as follows:
Figure 7.1 Diagram Power Triangle
In accordance with the Law of Pythagoras, the third link of the power can be determined mathematically as follows:
Cos α = Power On / Power Semu
Sin α = Reactive Power / Power Semu
From the above two equations we can turn into:
Active Power = Power apparent x Cos α
Pseudo Power = Power On / Cos α
Reactive Power = Power x Sin α Semu
So, if the two parameters are known, the other parameters can be determined. When the apparent power is known and large phase difference between the active power and apparent power is known, the value of active power can be determined. For example, note the apparent power S = 50 kVA, and the angle of the phase difference of 60 degree arc, then the active power P = 50 kVA x cos 600 = 25 kW
Another example, note the apparent power S = 50 kVA, and Active Power P = 25 kW, then the reactive power kVAr
Measurement of apparent power (Q) can be easily done by measuring voltages and currents in an alternating current circuit as shown in Figure 7.2.
Figure 7.2 Series of Power Measurement Semu (S) Direct