Injection type stator grounding protection method and system for large hydro-generator

Abstract

The invention discloses an injection type stator grounding protection method and system for a large hydro-generator. The injection type stator grounding protection method comprises the steps that a single-phase voltage transformer is additionally arranged at the neutral point of the generator; 20Hz voltage signals are injected from a secondary port of the single-phase voltage transformer through a20Hz injection power supply, and the protection device detects the injected voltage signals through a resistance voltage divider; the protection device detects an injected current signal through an intermediate current transformer to obtain 20Hz voltage and 20Hz current; the measured 20Hz voltage and 20Hz current are used to calculate a ground fault transition resistance value; and the calculatedground fault transition resistance value is used as a protection criterion, when the calculated ground fault transition resistance value is lower than a high-section constant value, an alarm action is executed, and when the calculated ground fault transition resistance value is lower than a low-section constant value, a tripping action is executed. According to the invention, the neutral point grounding mode of the generator is not changed, and the ground fault transition resistance value can be accurately calculated.

Description

Technical field[0001]The invention belongs to the technical field of relay protection for large-scale hydro-generators and power system main equipment, and specifically relates to an injection-type stator grounding protection method and system for large-scale hydro-generators.Background technique[0002]Stator single-phase grounding fault is the most common fault of large generator stator winding insulation damage. The main hazard to the generator is the burn of the stator core and the expansion of the ground fault to inter-phase or inter-turn short circuit. Therefore, the generator protects the A screen / B screen It has become a trend to configure different principles of stator ground protection (dual frequency and injection).[0003]The injection stator grounding protection has been widely used in the way that the neutral point of the generator is grounded with high resistance through the power distribution (seefigure 1 ), but when the neutral point of the large hydro-generator is grou...

AI Technical Summary

Problems solved by technology

In order to compensate the capacitive current, the inductance value of the arc suppressing coil is small, resulting in a small inductive reactance at 20Hz, resulting in a small 20Hz signal injected from the power supply unit to the neutral point of the generator when the injection stator grounding protection is applied. The measurement of the signal brings difficulties, which ultimately leads to unsatisfactory protection application effect

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