Transients based faulted feeder identification for ungrounded power distribution systems with distributed generations

Single phase faults in ungrounded power distribution systems cause small fault currents and are thus hard to locate. Besides, more and more distributed generations especially renewable generations are integrated into the power grid. The fundamental frequency short circuit current contributed by distributed generations (DG) could be small, and hence it is challenging to use overcurrent protection to protect distribution systems with DGs. This paper proposes a new travelling wave based protection method for identifying the faulted feeder. Traveling wave is generated by the faults and travels to the feeder head. Recording and analysis of the traveling wave features can help decide the faulted feeder. To increase the robustness and fault tolerance, Bayesian inference method is applied to combine prior information about feeder fault probability and IED recordings to determine the actual faulted section. The method is versatile and is applicable to feeders with or without DGs.