A novel ferroresonance and single-phase earth fault recognition method based on correlation analysis

In neutral ungrounded power system, ferroresonance overvoltage happens frequently, usually causes overvoltage, lead to potential transformer(PT) overheated and even explosion, and brings great threat to the distribution system. As the phenomenon of ferroresonance is very similar to single-phase earth fault, ferroresonance usually makes the misoperation of single-phase earth fault protection devices. In order to prevent the misoperation of protection devices, we must distinguish ferroresonance from single-phase earth fault. This paper analyses the feature of ferroresonance voltage and single-phase earth fault, and proposed a new ferroresonance and single-phase earth fault recognition method based on correlation analysis. We calculated the cross correlation coefficient between the voltage of ferroresonance and standard sine wave, then we calculated the cross correlation coefficient between the voltage of single-phase earth fault and standard sine wave. By comparing the coefficients, we found the difference between ferroresonance and single-phase earth fault. By building a distribution model in PSCAD, we got simulation data of ferroresonance and single-phase earth fault. We used the simulation data to verify the recognition method proposed in this paper. The results show that this method can distinguish ferroresonance from single-phase earth fault effectively.