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Keywords

small current grounding system, neutral point voltage, gear level adjustment, fault line selection, zero sequence current change, fault identification

Abstract

In order to solve the low accuracy of high-resistance grounding fault selection in small-current grounding systems, a multi-criteria grounding fault selection method based on the changing amount of zero-sequence current is proposed from the perspective of active regulation of neutral point voltage. Multiple grounding levels are uniformly set on the system side of the special grounding transformer. When a single-phase ground fault occurs in the system, the grounding level size is flexibly adjusted to suppress the fault phase voltage until no higher than the fault arc reignition voltage. If the fault arc can not be extinguished, the line will be judgedas a permanent ground fault line. In that case, the transformer grounding level will be decreased to amplify the fault feeder zero sequence currentand the non-fault feeder zero sequence current. The difference between the zero sequence current increase and decrease of each feeder before and after the lowering gear level can then be incorporated for line selection. Next, in the case of large transition resistance, the non-faulted feeder zero sequence current has a linear trend and the faulted feeder zero sequence current has a non-linear trend, and the degree of this non-linear distortion of each feeder zero sequence current can be exploited in line selection. Simulation results show that the method can achieve rapid extinguishing of the fault arc for transient grounding faults, can accurately identify ten kilo-ohm grounding fault feeders for permanent grounding faults, and effectively improving the accuracy of high resistance fault selection for small current grounding systems.

DOI

10.19781/j.issn.1673-9140.2022.04.012

First Page

105

Last Page

113

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