220 kV变电站主变低压侧跳闸典型故障分析与启示

Typical fault analysis and revelation of a low voltage side trip of a main transformer in a 220 kV substation

在各类电压等级的变电站故障之中,主变低压侧故障是较为常见的典型故障,此类故障往往依靠相关设备的后备保护动作切除,不可避免地扩大了故障范围｡为了解决此类问题,针对中性点经小电阻接地系统中一座220 kV变电站所发生的主变低压侧故障,运用对称分量法,结合录波图、相量图对其保护动作情况进行了分析,指出主变出口低压侧母线桥绝缘击穿是造成此次死区故障的原因。剖析了具有接地故障表征的死区故障特征。进而从发挥运行值班人员的主观能动性、提升设备运维综合化水平、提升主配网一体化调控系统智能化水平及改变电网供电模式等多个角度,对未来如何防范和缓解此类故障的影响提出了建议。

Among all kinds of power substation faults across various voltage levels,the low-voltage side fault of the main transformer is a common typical one.This fault is often dependent on the backup protection action of the relevant equipment for its removal.This inevitably enlarges the fault-impacted areas.In order to remedy this problem,the fault at the low voltage side of the main transformer in a 220 kV substation where the neutral point is grounded through the small resistance is investigated.The symmetrical component method is used to analyze the protection action,which is further combined with fault-recording and phasor diagrams.The insulation breakdown of the bus bridge at the low voltage side of the main transformer outlet is the cause of the dead zone fault.The characteristics of dead zone fault with grounding fault representation are analyzed.This should give full play to shift personnel’s subjective initiative,as well as improving the comprehensive level of equipment operation and maintenance,improving the intelligent level of the integrated dispatching and control system of the primary and distribution network,and changing the power supply mode of the power grid.Some suggestions are put forward to prevent and alleviate the influence of such faults in the future.