In view of the false alarm of the motor power supply fault and the"motor over-current"signal of a certain220kV transformer substation of Shangqiu Power Supply Company

it is found that this type of disconnector hassome defects in the design of the motor driving circuit. As a result of the design defect

of the thermal overload relayrunning for a long time

resulting in thermal relay coil overload failure

resulting in short-circuit power phase. Thecircuit has been redesigned by staff

finally

the problem of false tripping of power supply and false alarm of signal issolved

and some preventive measures are put forward.