Validation of the Harmonic-Based Method for Detecting Open-Neutral Fault in Low-Voltage Systems

The open-neutral fault occurring on the low-voltage feeder may result in overvoltage. This fault is very difficult to detect at the supply side of the feeder. To solve this problem, an idea that employs the sudden change of the third harmonic current in the feeder as the index to identify the open-neutral fault was proposed in the previous literature. This method can be accomplished by installing the embedded chip into the circuit breaker or other fault protective devices at the supply side of the feeder and therefore enhance their protection ability. The aim of this paper is to thoroughly investigate and validate the details of this method from the selectivity and sensitivity perspectives. In this paper, the procedure for the determination of the proper criteria to meet the selectivity requirement is introduced, and the detective rate to quantify the sensitivity of the detection method is proposed. The measurement based simulations and experiments were conducted as well to verify this method. The results are also presented.