1. Electric Power Research Institute of State Grid Hubei Electric Power Co. Ltd., Wuhan 430077, China;2. College of Information and Control Engineering, China University of Petroleum(East China), Qingdao 266580, China; 3. State Gird Hubei Energy Comprehensive Service Co. Ltd., Wuhan 430077, China; 4. Shandong Kehui Power Automation Co. Ltd., Zibo 255087, China

The electrical variation law of the single-phase-to-ground fault in distribution network after arc extinction do not only determines the over-voltage level whether the arc is re-ignited or the re-ignition electrical characteristics, but also affects the adaptability and reliability of the fault diagnosis method. The system fault recovery process is analyzed based on the single-phase-to-ground fault equivalent circuit of distribution network. It is found that the zero-sequence network in different grounding systems have an attenuated oscillation process after arc extinction. For ungrounded system, the zero-sequence voltage amplitude is large. The oscillation frequency is much lower than the power frequency and the oscillation time is long. The phase overvoltage will last for a long time. For arc suppression coil grounding system, the zero sequence voltage amplitude is large. The oscillation frequency is slightly larger than the power frequency, and the duration is generally above 5 cycles. The beat frequency phenomenon will cause overvoltage whose amplitude is within 1. 1 times of the normal level on the fault phase. For low resistance grounding system, the oscillation frequency is much higher than the power frequency. Its amplitude is small and the attenuation speed is fast. The correctness of the recovery process of single-phase-to-ground fault after are extinction in three types of grounding systems is verified by ATP-EMTP.