Single-phase-to-earth fault identification method for neutral point non-effectively earthed system

Abstract

The invention discloses a neutral point non-effective earthing system single-phase earthing fault identification method which includes the steps that a zero sequence voltage instantaneous value and a instantaneous saltation value are taken as the startup criteria of an identification scheme; when any of the above values is out of the limit, an identification process is started, a saltation moment is determined according to a signal saltation point, and the effective values of the zero sequence voltages and the three-phase voltages in cycles before and after the signal saltation point and the variations of the effective values are calculated; and a single-phase earthing fault is judged to have happened only when the variation of the zero sequence voltage and the variations of all phases of voltage all satisfy all the criteria. The method takes voltage variation for identification, and the saltation of the state of the system can be reflected; a low threshold value scheme is adopted in the method, so the system can be started sensitively under a high impedance fault; and the multiple criteria scheme of zero sequence voltage and three-phase voltage are adopted, so the method has high reliability. The method is simple and easy to realize.

Description

technical field [0001] The invention relates to a single-phase ground fault discrimination method of a power system distribution network, in particular to a "low threshold, multi-criteria" single-phase ground fault identification and detection method established by the voltage change before and after the fault in the power system distribution network. Background technique [0002] my country's distribution network mainly adopts neutral point non-effective grounding methods, including neutral point non-grounding and resonance grounding. It is found in actual operation that single-phase grounding faults account for about 80% of the total faults in this type of system. After a single-phase ground fault occurs, the fault phase voltage decreases, the non-fault phase voltage increases, the system line voltage remains unchanged, and the power supply is not affected. The system is allowed to continue to run for 2 hours, but long-term operation may cause the accident to expand or caus...

AI Technical Summary

Problems solved by technology

[0005] The purpose of the present invention is to provide a sensitive and reliable single-phase ground fault identification method to overcome the shortcomings of traditional methods that cannot be identified when a single-phase high-resistance ground fault occurs

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