The DC system has an important location in the substation. To ensure the long-term safe operation of a substation, its factors are various, among which the insulation problem of the DC system cannot be ignored.
The DC system of the substation is relatively complex. It is connected to the terminal row, terminal box and operating mechanism box of the outdoor distribution device through the cable trench. There is more possibility of grounding due to cable damage, insulation aging, damp, etc.
When one pole grounding occurs, the fuse is no short circuit current and can continue to operate, but it must also be found and eliminated in time.
Generally, the insulation resistance of various small buses, terminal circuits, and secondary cables of the DC system, measured with a 500V shaking meter, shall not be less than 0.5MΩ. The insulation of the DC circuit must be regularly monitored. Otherwise, it will bring many unsafe factors to the operation.