In order to analyze the cause of fault of a 550 kV oil-immersed inverted current transformer

the insulation performance of the equipment with same type and batch is studied by test.The reason of the fault is analyzed by way of disassembly after the test with combination of electric field simulation and corresponding preventive measures are proposed.It is shown by the result that partial discharge due to local field concentration and insulation degradation due to overvoltage is the main reason for the fault.For avoiding effectively occurrence of such fault

the delivery quality of such current transformer shall be subject to strict quality control and

at the same time

the insulation performance of the equipment in operation shall be detected periodically

corresponding tracking comparison database shall be set up and the issue of withstanding overvoltage shall be focused on in particularly so to demonstrate the insulation degradation degree of the current transformer and assure its stable operation.