Discharge in low voltage EPR DC cable under special situations

For low voltage DC feeder cable (<3000 V) for rail transportation, little attention has been paid by investigators on online monitoring technology in this area. This paper investigates the discharging condition of DC feeder cable, the characteristics of the discharge signals, and discusses the feasibility of discharge detection to assess the insulation state of this kind of cable. The results indicated partial discharges as U.Fromm proposed took place litter in DC feeder cable for the operation voltage is lower, but flashover of the cable will occur when it has a cut or crack in the insulation. The results also indicated that a cable operating at low voltage still could operate if there is a slight crack in its insulation. Thus, it is very important in practice to assess the state of the cable insulation through online detection of the discharge signals and avoid cable operation under conditions that result in a widening fault (crack or cut).