An adaptive reclosing strategy for UHV AC transmission lines based on phase difference of single-end induced voltage

In ultra-high voltage (UHV) AC transmission systems, single-phase to ground faults account for more than 80 % of all faults. If reclosing is performed blindly under permanent fault conditions after a single-phase to ground fault, the system may suffer severe secondary impacts. In order to solve this problem, the generation mechanism of the induced voltage at the fault phase after circuit breaker tripping is analyzed in the paper. Mathematical expressions for the fundamental component of the induced voltage under both permanent and transient faults are derived. Leveraging the phase difference in the fundamental component of the induced voltage between these two types of faults, a method for identifying the nature of single-phase to ground faults is proposed. Furthermore, considering the time requirements for arc extinction and reclosing, an adaptive reclosing strategy based on single-end phase difference is developed. The electrical quantities required for this method are easily measurable, and the signal sequences are readily accessible. Furthermore, it requires no additional equipment. This method can issue a reclosing signal within 0.06 s after fault clearance, thereby accelerating post-fault line recovery. Simulation results show that the adaptive reclosing method presented in this paper is unaffected by parameters such as fault grounding resistance, fault location, line length and operating power. It can accurately distinguish between different fault types with high reliability.