接地故障引起主变中性点设备损坏的分析

Analysis on the Damage of Transformer Neutral Point Equipment Caused by a Grounding Fault

某110kV线路单相接地故障时,因主变中性点引下线接头处发生锈蚀,热稳定性降低而完全烧断,引起主变中性点设备及多处电缆屏蔽接地线受损。结合现场检查结果与建模分析,发现经中性点构架接地的电缆屏蔽层,当线路发生不对称平衡故障时,若中性点接地不良,将会有很大的故障电流窜入,引起电缆屏蔽接地线受损,中性点构架电位升高,对二次元件造成反击损坏。

In a case of single-phase grounding fault of a 110kV line,the ground down-lead of the transformer neutral point equipment is corroded and blows out with its thermal stability decreased,which brings about the damages of the transformer neutral point equipment and the shield ground wires of several cables.In combination with the field checks and modeling analysis,it is found that when an unbalanced fault occurs in the line,if the neutral point is not well grounded,there would be a large amount of fault current flowing in,which would cause damage to the shield ground wires of cables and increase the electric potential of the neutral point structure,and finally lead to counterattack damage to the secondary components.