电厂6kV系统级联保护方案

Cascading protection scheme in 6 kV system of power plant

电厂6kV母线故障一般只能靠相邻元件的后备保护跳闸,时延较长。如果装设简易的快速母线保护(快母),则电动机的反馈电流、电动机启动或自启动等可能会误闭锁快母。提出了一种称为'级联保护'的母线保护方案,在原保护装置配置的基础上增加级联保护功能,采用立即闭锁、自动展宽、保护冗余的方法,结合方向元件、定值整定、监视闭锁通道等方法,较好地解决了这些问题,可在100ms内出口跳闸,大大缩短了母线故障的动作时间,可适用于电厂供电系统和厂矿企业供电系统。

Generally,the bus fault occurred in power plant 6 kV system can only rely on protections of adjacent element to cut off the fault which will delay too long.When simplified fast bus protection is applied,it may be locked in error because of the feedback current,start or self-start current of electromotor.As a solution of these problems,a fast bus protection scheme called ＂cascade protection＂ is proposed,which is not added in an additional device but in the normal protection devices.Combining the direction element,setting values and monitoring locking channel,some mothods are applied,such as fast lock,automatically stretching the locking signal,protection redundancy,etc,to avoid mis-lock the cascade protection.The tripping time of the new bus protection can be limited within 100 ms,which shortens the bus fault time significantly.The proposed scheme can be applied to power supply system in power plants as well as factories and enterprises.