A probabilistic-based technique using transient RMS currents for earth fault detection in medium voltage distribution networks

This paper presents a transient probabilistic-based technique for earth-fault detection in isolated and compensated neutral medium voltage networks. In these networks, the magnitudes of the fault currents are very small and the straight comparison of magnitudes may lead to risk of malfunction, especially at high fault resistance. The proposed technique is based on Bayesian theorem for selecting the faulted feeder using the transient RMS fault current for each feeder. The transient RMS value will be calculated from the residual currents of the feeders in a sliding window of 2.5 ms. The values of the currents will be normalized. Then it will be used to apply Bayesian theorem as probabilistic-based selectivity function to indicate the probability of the feeder to be faulted (or healthy). The faulted feeder can be detected easily without voltage measurements. The proposed technique is less dependent on the fault resistance and the faulted feeder parameters. The MV network is simulated by EMTP-ATP Draw program. Extensive simulations that cover different fault conditions are performed to validate the technique.