为了满足大型水电机组保护必须配备100%定子接地保护的要求,三峡水电站机组均配备了注入式定子接地保护. 在应用过程中发现随着运行工况的变化,注入式定子接地保护接地电阻测量精度会发生变化,即在发电机静态试验过程中将补偿参数调整准确后,在动态试验时测量结果却发生了变化,在发电机升至额定电压后测量结果又会发生变化. 为解决该问题,对注入式定子接地原理进行了分析研究,在对各项参数变化引起的误差展开分析的基础上,结合试验数据,找出了注入式定子接地保护在不同工况下测量误差大的原因,提出了自适应的注入式定子接地保护方案. 目前,采用自适应的注入式定子接地保护已在三峡水电站机组保护中投入运行,其在停机和运行状态下均保证了定子接地电阻测量的准确性.%As the large hydropower generator-unit must be equipped with 100% stator grounding fault protection, the voltage-injection-based stator grounding fault protection system is installed in all the generator units of Three Gorges Hydropower Plant. However, it is founded in application that the measurement accuracy of the grounding resistance of the protection system varies with different operation conditions. Although the offset parameters are set at accurate values in static test of the generator, the test results change in dynamic test and so do the measurement results when nominal voltage is attained in the generator. To solve this problem, a study on the mechanism of voltage-injection-based stator ground fault protection is carried out, in which the errors caused by the variation of the parameters are analyzed. According to the test figures, the causes of big measurement er-rors in different operation conditions of the protection system are founded out and a self-adaptive voltage-injection-based sta-tor grounding fault protection is proposed. The application of the proposed protection system in the generator-units of Three Gor-ges Hydropower Plant by far shows that the measurement accuracy of the grounding resistance can be assured when the generator is in or out of operation.
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