Ground Fault Detection of Small Resistance Grounding System Based on Improved Phase Current Abrupt Variable Method

Abstract

When a high fault resistance happens in a small resistance ground system, the protection device is simple to be unsuccessful to manage. By analyzing the characteristics of positive, negative currents in the additional state of fault, it is found that the fault detection method constructed only by the phase current increment relationship has risk of misoperation, but relationship among the magnitude of phase current increment can directly reflect the phase of the ground fault. At the same time, the phase location among the fault phase voltage and the current of the unhealthy part and non-fault line is different. Therefore, a ground fault protection method based on the correlation between the phase current increment ratio and the different phase angles of fault phase voltage and current is proposed. We choose the phase with the big phase current mutation as the grounding phase, and affect the fault part by the phase difference between the fault phase voltage and the current of the line. This eliminates the risk of protection maloperation only using the relationship between the size of current increment and protection sensitivity in case of high resistance fault. It can be used for fault phase selection, location, and multi-level protection. The correctness of the way is certificated by simulation.