In this type of system, Thristor's are used for switching of capacitors.. This is usually used in variable load conditions.

Automatic power factor correction is typical for large electrical systems with fluctuating load where it is common to connect number of capacitors to main power distribution station or substation. The capacitors are controlled by controller which continuously monitors the relative power demand. The relay connects or disconnects the capacitors to compensate for actual reactive power of the total load and reduce overall demand supply. Thyristors are used to switch the capacitors On and Off in the system.