A method suitable for generator injection type stator grounding protection

Abstract

The invention relates to a method for generator injection type stator grounding protection, which includes obtaining a calculation formula of the load resistance of the secondary side of a grounding transformer through an equivalent circuit of the stator grounding protection, and deriving the injection signal and power generation of the injection type stator grounding protection. The functional numerical relationship between the parameters of the grounding transformer at the neutral point of the machine is calculated; then the transformation ratio n of the grounding transformer is calculated when the injection signal, voltage-signal ratio, and current-signal ratio take extreme values. ex ;If the 20Hz voltage injected into the stator winding side of the generator is less than 1% of the rated voltage of the generator, the transformation ratio n of the grounding transformer is n ex ; Otherwise, first take the 20Hz voltage that is closest to 1% of the rated voltage of the generator and injected into the stator winding side of the generator, and then calculate the optimal grounding transformer transformation ratio n and the secondary side load resistance value of the grounding transformer to realize the stator grounding protection. . The invention has the characteristics of improving the sensitivity, improving the protection injection power, and realizing the optimization of the protection function.

Description

technical field [0001] The invention relates to a motor stator grounding protection technology, in particular to a method suitable for generator injection type stator grounding protection. Background technique [0002] With the increase of the single-unit capacity of the generator in the power system, the capacitance of the generator stator winding to the ground also increases, and the site puts forward higher requirements for the single-phase grounding protection of the generator stator. Among them, the single-phase ground fault of the stator winding is the most common fault of the generator set. Although the single-phase ground fault of the stator winding is less destructive to the equipment itself, it is a precursor to the more destructive inter-turn or inter-phase short-circuit fault. [0003] The 20Hz injection type stator grounding protection constitutes the current criterion of protection according to the characteristic that the 20Hz signal current after the single-p...

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Problems solved by technology

If the ratio of the 50Hz signal component to the 20Hz signal component is large, the 20Hz voltage and current signals transmitted to the protection device will be very small, which will affect the accurate measurement of the protection, resulting in a decrease in the measurement accuracy of the injection stator grounding protection, and the protection injection power cannot be realized. Maximization and optimization of protection functions

[0006] Therefore, in the existing 20Hz injection stator ground protection method, the transition resistance affects the protection sensitivity, and the transformation ratio of the ground transformer will affect the 20Hz voltage injected into the stator winding side, which cannot achieve the maximum protection injection power and the maximum protection function. optimization

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