Experimental study of surge protective devices to apply in dc power supply system at power substation

Impulse interferences appear in DC power supply system when switching, short circuits or lightning strokes to substations occur. Interferences under consideration result in malfunctions of relay protection and emergency situations. To mitigate these interferences, at present, avalanche diodes or surge protective devices (SPDs) mainly based on metal-oxide varistors with gaps are used. Protective devices are installed on positive and negative pole of DC power supply main switchboard using common mode scheme. Specific high-frequency diodes are not applied because they allow low currents only.