Detection of three‐phase fault during power swing using zero frequency filtering

Summary Distance relay is susceptible to maloperation during power swing. Power swing blocking function is integrated in distance relays to ensure security during power swing. However, if a fault occurs during power swing, it must be detected and cleared by the relay as quickly as possible. Since power swings and three‐phase faults are both balanced phenomena, discriminating them is very challenging. This paper proposes a method to detect three‐phase fault during power swing by computing the Hilbert envelope of the current waveform followed by zero‐frequency filtering. The average rate of change in amplitude of the zero‐frequency filtered current is used as the fault detector index. The discrimination capability between three‐phase fault and power swing of the extracted feature is the main contribution of this paper. Results of various possible test cases simulated through EMTDC/PSCAD show that the proposed method is fast and reliable in detecting three‐phase faults during power swings.