基于额定电压因数的长电缆线路PT保护措施

Research on PT protection measures for long cable lines based on rated voltage factor

高铁长距离电力线路已逐步实现全电缆化,而部分高铁供电系统仍采用小电流接地方式。因此,当系统单相接地时常伴随着间歇性电弧接地现象,造成了部分电压互感器(PT)的损坏。为解决长电缆线路PT损毁现象,在不改变中性点接地方式和线路结构的前提下,分析高铁长电缆线路PT烧损的主要原因;通过构建仿真模型,指出铁路长距离电缆线路小电流接地系统除应按照不接地系统进行电气设备选型及绝缘配合设计外,宜选用励磁特性饱和点较高的电磁式PT,PT额定电压因数宜大于2.2 p.u.;并将该方案应用在以无锡东为例的多个高铁长电缆线路配电所内,均取得良好效果,验证了该方案的可行性。

High-speed rail long-distance power lines have gradually realized full cable,and some high-speed rail power systems still use neutral point ungrounding.Therefore,when the system is single-phase grounded,it is often accompanied by intermittent arc grounding,which causes damage to some PTs.In order to solve the PT damage phenomenon of long cable line,the main reason of the PT burnout of high-speed long cable line is obtained through theoretical analysis without changing the grounding mode and line structure of the neutral point.Then,by constructing the simulation model,the railway is pointed out.In the long-distance cable line,the neutral point ungrounded system should be designed according to the ungrounded system for electrical equipment selection and insulation coordination.The electromagnetic PT with higher excitation point saturation should be selected.The PT rated voltage factor should be greater than 2.2 pu;The scheme is applied to a number of high-length cable-length cable distribution stations in Wuxi East,and good results have been obtained,which verifies the feasibility of the scheme.