水轮发电机转子一点接地故障分析及处理

摘要

This paper analyzed one point grounding fault of a large hydroelectric generator and located the grounding fault, and found that the single-phase grounding of the low voltage side of the excitation transformer will cause the rotor grounding protection action, and also found that if the low voltage side of excitation transformer is △connection and excitation rectifier circuit using 6 pulse rectifier circuit, the variation of excitation current and voltage and the operation of the excitation differential protection are not necessarily related to the single-phase grounding at the low voltage side of the excitation transformer. In this paper, through the rotor one point grounding treatment, the following conclusions are obtained, when the generator is in the idling state, the rotor ground protection is normal and the excitation grounding action is taken, and the calculation value of the grounding fault position is about 50%, it is necessary to consider whether the 50% position of the excitation winding is grounded or not and the possibility of single-phase grounding at the low voltage side of the excitation transformer at the same time, and even if the excitation current and voltage are not changed or the excitation differential protection is not operated, we can not to judge that the excitation transformer is not grounded at the low voltage side. The conclusions obtained in this paper have important reference value and field basis for the treatment of the same type of fault. According to the conclusion of this paper, in practical application, misleading of the fault location data of protection device can be avoided in the process of fault finding, thus improving the efficiency and accuracy of rotor one point ground fault processing.%本文对某大型水轮发电机转子一点接地故障进行了分析和查找,发现了励磁变压器低压侧单相接地会引起转子接地保护动作,同时还发现如果励磁变低压侧为△接线且励磁整流电路采用6脉动桥式全控整流电路,励磁电流和电压的变化以及励磁变差动保护动作与励磁变低压侧单相接地没有必然联系.本文通过此次转子一点接地的处理,得出以下结论,当发电机在空转状态下转子接地保护正常而加励磁后接地保护动作,且接地故障位置计算值在50%左右时,应该同时考虑励磁绕组50%位置是否接地以及励磁变低压侧单相接地的可能,而且不能仅从励磁电流和电压未变化或励磁变差动保护未动作来判断励磁变低压侧没有接地.本文得出的结论对同类型故障的处理有重要的参考价值和现场依据.目前尚未见到针对励磁变低压侧单相接地对转子保护动作影响的相关文献.根据此文结论,在实际应用中,可以避免在故障查找过程中被保护装置故障定位数据所误导,从而提高转子一点接地故障处理的效率和准确性.