A novel ferroresonance recognition method based on the excitation characteristic of potential transformer

In neutral ungrounded system, ferroresonance occurs frequently and brings great threat to the safe and stable operation of distribution network. Ferroresonance causes overvoltage and overcurrent (zero sequence) in the system, lead to the misoperation of single-phase earth fault protection devices, makes potential transformer (PT) overheated and even destroys PT. In order to prevent the misoperation of protection devices and take effective measures to restrain ferroresonance timely when ferroresonance happens, we must recognize ferroresonance accurately. This paper proposes a recognition method of ferroresonance based on the excitation characteristic of PT. We set up a 10kV distribution network model in PSCAD to simulate ferroresonance, and applied the ferroresonance data obtained by simulation to verify the ferroresonance recognition method proposed in this paper. The verification results show that this method can effectively recognize ferroresonance, and accurately distinguish ferroresonance and single-phase earth fault.