关于一起汽轮发电机定子接地保护动作的分析与处理

Analysis and processing on an operation of the stator ground protection of a set of gas-generator

某电厂一台210 MW汽轮发电机的三次谐波定子接地保护动作后,通过对该保护A、B屏有关数据的分析比较,排除了该发电机在中性点附近发生定子单相接地故障的可能。经检查,发现了该保护回路中的接线错误,重新接线后,使保护恢复了正常。并对该保护动作方程中的变比平衡系数进行了分析,给出了计算方法,结合实测数据,在不同的变比平衡系数下,对该保护的动作量和制动量进行了理论计算。通过对比分析,并考虑到发电机中性点接地方式的特点,指出了该保护在应用上和定值整定上存在的问题。

After operation of stator ground protection based on the third harmonic in a power station that have a set of 210 MW gas-generator, the possibility of single-phase grounding fault was obviated near the generator stator neutral point by comparing and analyzing about A and B screen＇s data. After checking,it found out the connection error in the protection circuit and made the protection under normal condition after re-connection; then analysed the transformer ratio balance coefficient in the action equation of the protection ,gave its calculating method, according to different transformer ratio balance coefficient and the actual measured data, calculated theoretically the action value and resistance value. After comparing and analyzing ,and considering the feature of the generator neutral point grounding, it points out the problem of protection on application and setting.