Parameters of passive ferroresonance suppression circuit (FSC) affecting ferroresonance damping and normal operating voltage and current of capacitive voltage transformer (CVT)

This paper discusses the effect of parameters of passive Ferroresonance Suppression Circuit (FSC) on Capacitive Voltage Transformer (CVT) in not only the mitigation of ferroresonance oscillation, but also the normal operating voltage and current of CVT. The passive FSC composed of a resistor paralleled with a saturable reactor that has been a series circuit of a resistor and a saturable inductor. In this study, the resistance values have been varied. Then, one of the resistance variations has been used to damp the ferroresonance oscillation during the simulation with load variation of CVT. The opening and the reclosing of the circuit breaker have been utilized to initiate the ferroresonance on CVT. The results have showed that the existence of passive FSC with the given parameter values could effectively suppress the highly distorted overvoltage and overcurrent of ferroresonance oscillation, but the normal operating voltage and current of CVT have been increased during FSC resistor variation and have been decreased during saturable reactor resistor variation. The resistance value of FSC has been linear with the peak voltage and the ripple of waveform, whereas the resistance value of saturable reactor has been opposite with the peak voltage and the ripple of waveform. Furthermore, the load variation of CVT affected the ferroresonance behaviour and the peak voltage and current of CVT. Regarding those results, the electrical engineer should be able to choose the design of FSC appropriately in order to not only get the effective ferroresonance mitigation, but also to maintain the normal operating conditions of CVT in the future.