Online Monitoring Method of Turn-to-Turn Short-Circuit Faults in Dry-Type Reactors Based on Phase Angle Difference

Due to the difficulty of real-time monitoring, frequent turn-to-turn short-circuit faults in the windings of dry-type reactors pose serious problems to the dependability of power distribution. To address this issue, this study proposes a novel fault identification method based on the phase angle difference variation rate (η), enabling real-time fault detection and early warning of insulation degradation. A systematic investigation was conducted on parameter variation characteristics during single-turn short-circuits at different winding locations. Simulating insulation deterioration reveals evolving winding currents and phase angle differences. The results demonstrate that the phase angle difference variation rate (η) exhibits the most pronounced and detectable changes among all parameters. Critical thresholds for insulation degradation and breakdown were identified at 100 mΩ and 10 mΩ, respectively. According to simulation and experimental results, the degree of inter-turn insulation degradation can be precisely determined by tracking the phase angle difference rate. The inter-turn insulation is in a normal state when η≤30%, in a degradation stage when 30%