This Article provides a detailed technical understanding of the kWh vs kVAh regime and charts out the need for reactive power in the electricity distribution system and importance of reduction of reactive power.
Power Factor: Power factor (pf) is defined as the ratio of active power to the apparent power of the system i.e. pf = kWh/kVAh
As shown in Fig, the quantities P, Q and S are represented by a power triangle.
Power factor ratio is also equal to the cosine of the phase angle between true power and apparent power. It should be noted that power factor, like all ratio measurements, is a unitless quantity.
As can be seen from the figure above, “power factor” can also be defined as the cosine of the electrical angle between the voltage and current vectors in an AC electrical circuit. However, power factor is not dependent upon the magnitude of the voltage and current but the phase angle between the voltage and current vectors.
The active power (kWh) is actually consumed by the electrical equipment and converted into work for creating heat, light, motion etc. However the reactive power (kVArh) is just used to provide the electromagnetic field in the inductive equipment, stored up in the windings of the equipment. Therefore while the kWh power is actually put to work, the kVArh power is just required to convert the electrical power into work.
Electric power has two components – active power (kWh) and reactive power (kVArh). The active and reactive power components combine to form the apparent power (kVAh). The apparent power can be calculated as a Pythagoras sum of active power (kWh) and reactive power (kVArh).
Source - MSEDCL Presentation on KVAH