Analysis of a 110 kV substation 1# main transformer protection maloperation and research of the reformation programme

A 110 kV substation 1 # main transformer fault component differential protection had an unwanted operation.After a comprehensive inspection to the 1# main transformer equipment,the secondary circuit and the protection equipment and a detailed analysis of the course of the operation of the relay protection and the accident report,it is confirmed that the defective design principle of the fault component differential protection of the main transformer protection equipment is the fundalmental reason of that unwanted operation.Through upgrading of the software of the 1# main transformer fault component differential protection,the logic circuit of the software is given a criterion of non-differential current beore 2 circyls and an assistant criterion for braking of steady component and low ratio,unwanted operation of the fault component protection can be effectively prevented.After upgrading of the software,the differential protection equipment is to be comprehensively inspected according to the standards for the newly installed electrical equipment.It must pass the inspection before to be put into operation.