大型火电厂低压厂用电系统单相接地越级跳闸解决方案

Solutions of Single Phase Grounding Override Trip of Low-Voltage Station Power System in Large Power Plant

发电厂400 V低压厂用电系统部分线路较长且运行环境差,因电动机控制中心(MCC)段的相间短路保护与动力中心(PC)馈线的零序保护没有配合整定,当MCC段馈线开关发生金属性或非金属性接地故障时,出现越级跳闸导致母线失压事件的发生,或者出现MCC和PC段零序保护均不动作的情况,可能引发人员触电和电气火灾事故,严重影响低压厂用电系统运行的可靠性,给发电企业造成较大的经济损失。通过分析越级跳闸事故案例,提出相应的保护整定建议及保护配置方案。

The 400 voltage station power electric power line in the power plant mostly are long and the operating environment usually is poor. Because the two phase short-circuit protection of the motor control center(MCC) bus does not match with the zero sequence protection of the power center(PC) bus,it is possible that when the feeder switch of the MCC bus has a metal grounding or non-metal grounding and override trip occur,the bus voltage may loss,or the zero-sequence protection of the MCC bus and the PC bus does not act,it may cause personal electric shock and electrical fire accidents,seriously affect the reliability of low-voltage power system,and cause great economic losses to power plant. Based on the analysis of override tripping accident cases,this paper puts forward the corresponding protection setting suggestions and protection configuration plan.