Analysis and processing on acting of differential protection of transformer

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.