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

Abstract

The invention discloses an injection-type stator grounding protection method and system for a large-scale hydro-generator, comprising: adding a single-phase voltage transformer at the neutral point of the generator; A 20Hz voltage signal is injected into the secondary port, and the protection device detects the injected voltage signal through a resistive voltage divider; the protection device detects the injected current signal through an intermediate current transformer to obtain 20Hz voltage and 20Hz current; use the measured 20Hz voltage and 20Hz current to calculate Obtain the ground fault transition resistance value; use the calculated ground fault transition resistance value as the protection criterion, when the calculated ground fault transition resistance value is lower than the high stage fixed value, the alarm action will be executed, when the calculated ground fault transition resistance value When the value is lower than the low-level setting, the tripping action is performed. The invention does not change the grounding mode of the neutral point of the generator, and can accurately calculate the transition resistance value of the grounding fault.

Description

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

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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