Third harmonic voltage stator grounding protection method

Abstract

The invention discloses a third harmonic voltage stator grounding protection method. The third harmonic voltage stator grounding protection method comprises the steps of calculating a positive-sequence voltage of a power generator end, a third harmonic voltage of a neutral point and a zero-sequence third harmonic voltage of the generator end; judging whether a zero-sequence PT of the generator end is broken or not, and shunting protection if the zero-sequence PT of the generator end is broken; judging whether a neutral point voltage loop is broken or not, and shunting protection if the neutral point voltage loop is broken; synthesizing a differential voltage and a brake voltage according to the third harmonic voltage of the neutral point and the zero-sequence third harmonic voltage, corrected by an automatic adjustment system, of the generator end, and performing protection action when the differential voltage is larger than the brake voltage and the zero-sequence PT of the generator end and the neutral point voltage loop both are not broke; and comparing a specific value between the zero-sequence third harmonic voltage of the generator end and the neutral point third harmonic voltage with a protection fixed value, and performing protection action when the specific value is larger than the protection fixed value and the neutral point voltage loop is not broken. No maloperation is generated when the zero-sequence PT of the power generator end and the neutral point voltage loop are broken, and the third harmonic voltage stator grounding protection method is high in reliability.

Description

technical field [0001] The invention relates to a third harmonic voltage stator grounding protection method, which belongs to the technical field of generators. Background technique [0002] The stator grounding fault current of large generators is relatively large, and the stator core is burned seriously, which is easy to cause phase-to-phase short circuit or inter-turn short circuit. The correct configuration of stator grounding protection is very important for the safe operation of the unit. Large-scale generators basically adopt dual protection configuration, among which at least one set of stator ground protection adopts the third harmonic voltage protection and fundamental wave zero-sequence voltage protection to form a dual-frequency stator ground protection. [0003] Fundamental zero-sequence voltage protection is simple and reliable, but there is a dead zone near the neutral point. There are many types of third harmonic voltage protection, all of which can respond ...

AI Technical Summary

Problems solved by technology

[0006] The purpose of the present invention is to overcome the deficiencies in the prior art, provide a third harmonic voltage stator grounding protection method, solve the lack of consideration of generator zero-sequence voltage circuit disconnection in the third harmonic voltage stator grounding protection in the prior art, and easily Technical problems of disconnection protection malfunction

Images