In power systems, phase shifts occur between the voltage and the current
, which change over the length of the power system and depend on the reactances of the power system and the load. The phase shifts illustrate how well or poorly the matching between inductive and capacitive loads is. The actual power present at any point on the power system is calculated by taking the product of the voltage and the current, taking into account the phase shift with the cosine between the two amounts. The Var (Voltage-Ampere Reactive) value is the apparent power. It is the product of the two magnitudes taking into account the sine of the phase angle between the voltage and current. The Var value shows the inequality between the phase angle of
voltage and current. In power grids, it is mainly the apparent power that is usually expressed in kilo-Var (kVar) or mega-Var (MVar). If the phase shift between voltage and current is too large, it is compensated with a static power factor correction.