关键词: 中性点接地装置, 故障电流, 暂态过电压, 中性点位移电压, 巨型水轮发电机组

Abstract: The unit capacity of generators applied in Wudongde Hydropower Station and Baihetan Hydropower Station are 850MW and 1000MW respectively, whose unit capacity and voltage level of generators exceed the engineering experience. Generator neutral grounding equipment is one of the most important auxiliary equipment. Parameters configuration is determined by phase to ground capacitance of generator stator circuit. If adopting traditional high resistance grounding, as the phase to ground capacitance of generator stator circuit for giant generator is so high that grounding fault current of generator can not meet the limiting value proposed by standards. To this end, a study is carried out. Firstly, the fault current limiting value of iron core ablation is proposed; then compensating reactance grounding method is proposed based on transient overvoltage and grounding fault current; at last, the neutral shift voltage calculation method for compensating reactance grounding method is proposed. The giant generator neutral grounding method should be determined according to grounding fault current, transient overvoltage and neutral shift voltage.

Key words: neutral point grounding equipment, fault current, temporary overvoltage, neutral point displacement voltage, giant generator