A new control unit for electronic ferroresonance suppression circuit in capacitor voltage transformers

Ferroresonance suppression circuit (FSC) as an important portion of capacitor voltage transformer (CVT) has a vital role in the prevention of overvoltages. There are three types of FSC: active, passive and electronic type. In this paper, a new control unit is proposed for electronic FSC (EFSC) to damp out oscillations and overvoltages of ferroresonance as quickly as possible. The proposed control unit is installed at the secondary side of the CVT and takes samples from the output voltage and then switches on the silicon-controlled rectifier (SCR) according to the overvoltages level. In the proposed control unit, the SCRs are switched off automatically after the disappearance of overvoltages. Thus, a separate command circuit is not required for generation of negative pulses to switch off SCRs. In addition, phase detector unit, firing circuit and separate source for SCRs triggering are omitted from the control unit. All simulation studies are conducted in the Multisim software environment. The obtained results show that the designed control unit has very fast response and desirable stability in different operation conditions. Moreover, frequency response and CVT transient response are not affected by the proposed electronic control unit.