短路故障对部分接地方式下220 kV变压器影响分析

220 kV变压器通常采用部分接地方式,因系统容量增加,短路故障引发变压器故障时有发生.分析了220 kV变压器中性点绝缘承受过电压的能力,计算了220 kV变压器承受短路的限度,以及单相短路时中性点的过电压.结合实例,分析了单相短路和非全相运行时对不接地变压器中性点绝缘的影响,以及各种短路故障时接地变压器的耐热稳定性和耐动稳定性.指出短路故障通常不会直接导致中性点绝缘击穿,但若有其他过电压共同作用,则很可能会引起中性点绝缘击穿;而通过中性点直接接地变压器的短路电流已经很接近其承受短路的限度,建议采取限流措施,或者改变220 kV变压器的接地方式.

Analysis of Effect of Short Circuit Fault on 220 kV Partial Grounding Transformer

Partial grounding is usually applied to 220 kV transformers, With increase of the capacity of power system, transformer faults caused by short circuit fault occurred now and then, The capability of the neutral point of 220 kV transformers enduring over voltage is analyzod, The limit of 220 kV transformer enduring short circuit fault and the over voltage of neutral point caused by single-phase fault are analyzed, According to the fault case, the effect of singe-phase fault and open phase to transformer neutral insulation is analyzed. The thermal resistance stability and dynamic.resistance stability of transformers enduring short faults are evaluated, It is concluded that though neutral insulation usually cannot be broken down by single-phase fault, it is dangerous when there is other over voltage acting together, Given the short current of transformers with neutral point grounding directly is already close to its limitation, the current limiting measures are suggested or changing the grounding methods may take effect.