Grounding protection method for stator of dual-frequency injection type power generator

Abstract

A dual-frequency injection-typed generator stator grounding protection method pertains to the field of power system main equipment relay protection technology. Firstly the generator operation frequency is detected; when the generator operation frequency is more than 10Hz and less than 40Hz, the injection power frequency is taken as 100Hz; when the generator operation frequency is not more than 100Hz or not less than 40Hz, the injection power frequency is taken as 20Hz. According to the injection frequency, a shift switch selects a corresponding 100Hz bandpass filter or 20Hz bandpass filter so as to inject an injection signal to the neutral point of the generator by a secondary side winding of a distribution transformer through the filter. The injection frequency signal of secondary side pressure and current quantitatively calculates the grounding fault resistance of the generator. The method adopts the dual-frequency injection to eliminate the signal influence of the generator body, protect the operation dead zone and achieve the stator grounding protection in the whole process of starting and shutting the generator, which can be used for stator grounding protection of large-scale generator set, pumped storage unit or gas turbine set.

Description

technical field [0001] The invention belongs to the technical field of relay protection for main equipment in a power system, and in particular relates to a stator grounding protection method for a dual-frequency injection type generator. Background technique [0002] According to statistics, the stator grounding fault accounts for a considerable proportion of the main body faults of generators with more than 100MW in the country every year. The generator stator ground fault is often the precursor of more serious phase-to-phase short-circuit or inter-turn short-circuit faults. The reliable and sensitive operation of the stator ground-ground protection can greatly reduce the probability of these serious faults. If the ground fault current is limited within the safe ground current range, the stator core of the generator can be protected from damage, and the direct and indirect economic losses caused by the fault will also be greatly reduced. For generator sets of 100MW and ab...

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Problems solved by technology

There are patents for stator grounding protection of external power generators, such as the generator stator grounding protection method (ZL00114451.0), the neutral point through the arc suppression coil grounding generator fixed value grounding protection method (ZL03143978.0), these methods are subject to the Influenced by the operating frequency of the generator, the stator grounding protection cannot be realized in the whole process of starting and stopping the generator

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