In recent years the harmonic producing part of total load has increased continuously because of the massive usage of power electronic in all the voltage levels. Thyristor convertors, frequency convertors, thyristor switches and static var compensator, such as thyristor controlled reactors (TCR) and thyristor switched capacitors (TSC), are commonly adopted in industrial applications and power utilities. Filter capacitor banks consist of capacitor bank and series connected air core. Their task is to absorb the harmonic currents generated by loads and all above mentioned power electronic devices. The aim of NC020 is to provide a reliable and cost effective solution for such an application granting capacitor bank safe operations.