The fixed DC de-icing device converts AC power to adjustable DC voltage through a thyristor rectifier valve. The voltage is then passed through a smoothing reactor and a DC de-icing switch to be connected to the transmission line that needs de-icing, thus forming a DC circuit on the line. Due to the resistance of the transmission line, the DC current passing through will raise the temperature of the line, thereby melting the ice on it and achieving the de-icing purpose. 

Meanwhile, by controlling the triggering angle of the thyristor valve, the magnitude of the DC current added to the transmission line can be continuously and precisely adjusted in real time, thereby accurately controlling the temperature of the transmission line and achieving safe and effective line de-icing. 

The fixed DC de-icing device can safely, efficiently and rapidly perform fully automatic intelligent de-icing on transmission lines and ground wires of 66kV, 110kV and above voltage level substations in power systems that are prone to ice and snow freezing disasters.