A study on factors influencing ferroresonance in distribution system

Ferroresonance due to transient impact is a common phenomenon in ungrounded distribution system. It is a great threat to the security of power system. Highly nonlinear magnetizing inductance of the potential transformer and zero sequence capacitance of the system may cause low, high or fundamental frequency resonance. On the basis of analyzing the mechanism of ferroresonance, an equivalent model of a 10kV distribution system is established. A simulation model of the 10kV distribution system is built using saturable transformer model in MATLABSimulink. Simulation results reveal as follows: zero sequence capacitance of the system determines types of ferroresonance caused by single phase-to-ground fault; magnetizing resistance, DC resistance of the high-voltage winding and magnetizing characteristic of the potential transformer principally determine whether ferroresonance occurs or not and its amplitude.