关于一起变压器差动保护动作的分析与处理

Analysis and processing on acting of differential protection of transformer

某电厂210MW汽轮发电机组的厂高变差动保护动作后,通过对故障数据的分析,排除了保护区内一次设备故障的可能,判断该保护动作的直接原因是电流二次回路故障引起。通过现场检查,证实了以上的判断,这大大缩短了机组停运的时间。同时对差动保护的差流越限,CT断线的判据进行了讨论,指出:不当的差流越限整定值,保护启动后缺乏必要的故障性质的判断是保护误动的重要原因。针对以上情况,提出了保护在运行、巡查、校验及定值整定方面采取的措施,保护的可靠性得到了提高。

After differential protection operation of station service high voltage transformer for 210 MW gas-generator set in a power plant,the possibility of primary equipment fault on protected area is obviated via fault data analysis.It judges that the direct reason of protection acting is secondary circuit fault.By on site checking,the above is confirmed,which greatly shortens the time that generator set stopped.And through analyzing the over setting of differential current and criterion of CT break,it points out that improper over setting of differential current and lack of judgement of failure type after protection startup result in the protection maloperation.In allusion to the above problems,measures should be taken in terms of operation,inspection,checking and setting of protection to improve the reliability of protection.