发电机中性点经消弧线圈谐振方式接地中串联电阻对定子接地保护的影响

以三峡水轮发电机为例 ,阐述了大型水轮发电机中性点经消弧线圈接地的必要性。通过计算说明在消弧线圈中串联小值电阻可以起到限制传递过电压的作用 ,须注意的是电阻阻值的选取应从补偿电容电流和限制传递过电压两方面加以验算。在经耦合电容引起的传递过电压满足定子绕组绝缘要求时 ,应注意校验其对基波零序电压定子接地保护动作可靠性的影响 ,实例分析说明此传递过电压可引起基波零序电压定子接地保护的误动。

Effects of series resistance on stator ground fault protection of large-capacity generator by resonant neutral grounding

Taking the hydro-generator for the Three Gorges power plant as an example, this paper expounds it is very necessary for large_capacity hydro-generator to adopt arc-extinguishing coil grounding. In resonant neutral grounding a small series resistance in the branch of arc-extinguishing coil can play the role to limit the transferring over-voltage, and its value must be checked from two sides of transferring over-voltage and fault current. The transferring over-voltage caused by coupling capacitance meets the insulation level of generator, the reliability of stator ground fault protection using fundamental zero-sequence voltage ought to be analyzed considering the influence of the transferring voltage, the cases verify the transferring voltage can cause the maloperation of protection.