Simulation Analysis of Inter-turn Short Circuit Fault of Dry-type Air-core Reactor

In this paper, an inter-turn short circuit fault of dry-type air-core reactor is analyzed by on-site inspection and protection record analysis. It is determined that the fault process is that the inter-turn short circuit of C-phase reactor leads to a sharp rise in temperature, and the internal winding melts and drops to cause single-phase grounding, and gradually develops to B and C inter-phase short circuit fault. Based on ATP software, a capacitor bank switching model is built. By simulation analysis, it is determined that the cause of the fault is that when the capacitor bank is put into operation, an over-voltage of 6.25 times is generated at both ends of the series reactor. Under the over-voltage, the weak point of the inter-turn insulation of the reactor is broken down, causing inter-turn short circuit. Furthermore, the fault development process of inter-turn short circuit is simulated. The simulation results are basically consistent with the recorded voltage and current waveform. The whole process of inter-turn short circuit developing to inter-phase short circuit fault is reproduced, which verify the accuracy of the analysis.