从一次故障保护不正确动作,分析电流互感器变比选择及其10%误差的影响

From one maloperation of fault protection to analyse CT ratio selection with its 10% error influence

电流互感器的伏安特性偏低,短路电流倍数偏小是保护装置不能正确反应一次电流大小,进而影响保护正确动作的主要原因之一。针对220kV白家庄站35kV黄丹沟Ⅱ回线线路发生故障而越级到主开关掉闸的问题提出了保护CT如何选择变比以及如何计算10%误差和短路电流倍数。

Because of the low volt-ampere characteristic of CT and low multiple of short circuit current, the protection device can not measure primary current correclty, and it is an important reason for the maloperation of protection system. Based on the problem that when a fault occurs on Huangdangou 35 kV line Ⅱ, which is located in 220 kV Baijiazhuang substation, the main switch jumps, a method on how to select the ratio of protection CT and calculate the multiple of short circuit current within 10% error is proposed.