This paper analyzes the a typical over-voltage fault caused by the misoperation of DC ice-melting device. It is pointed out that the direct cause of this failure is that the AC voltage output from the DC melting device reacts to the device itself and due to the protection of the surge arrester
the ice melting device can still be used normally. According to the cause of the fault
some suggestions are put forward to improve the design of the current DC melting device.