Modeling and Analysis of Transient Equivalent Circuit of Grounding Fault in Distribution Network with Neutral Point Grounded Through Low Resistance

Abstract

There are three main neutral grounding modes in medium voltage distribution network: neutral ungrounded mode, neutral grounded through arc suppression coil mode and neutral grounded through low resistance mode. When the neutral point is grounded through low resistance in distribution network, the fault current is small in case of high resistance grounding fault. The sensitivity of using steady-state electrical quantity to realize protection is poor. In fact, the transient fault current in the initial stage of fault occurrence is large, which can be used as an effective protection characteristic quantity. Transient equivalent circuit is the main tool of fault transient analysis, so it is necessary to accurately model the transient equivalent circuit. Firstly, the transient equivalent circuit of single-phase grounding fault in low-resistance grounding distribution network is established. Secondly, the transient and steady-state zero sequence currents of each outgoing line and neutral point are theoretically calculated, and their distribution laws are summarized. Finally, the correctness of the transient equivalent circuit and the theoretical calculation results are proved by simulation in MATLAB. This paper provides theoretical support for the grounding fault protection of low-resistance grounding distribution network based on transient electrical quantity.