Grounding Design And Fault Monitoring On High-Speed Railway Feeder Cable

Development of High-speed railway in china is quickly, the using of cable is gradually increased. Overhead bare wires is used as feeder in the past, now is being replaced by cables. Feeder cable is27.5kV high voltage single core cross-linked polyethylene(XLPE) cable. The alternating current that flowing through the cable conductor leads to induced electromotive force, the magnitude of the induced electromotive force is proportional to the length of cable and the magnitude of current. When the sheath induced electromotive force is too large, would endanger the security of persons and equipment, even cause the cable grounding fault.Take different sheath grounding methods and protection for different length of feeder cable. In three cases(Power frequency steady-state, power frequency overvoltage, lightning current impact)different grounding is theoretical analysised, to explore the feasibility of the grounding and protection. Then PSCAD/EMTDC software is used to build simulation model including the traction substation, the feeder cables, the model of OCS(overhead contact system), locomotives and other models. On the basis of theoretical analysis, the induced voltage of feeder cable sheath is simulated to verify the correctness of the grounding. When the length of feeder cable less than1000m, with one end direct grounding, the other protection grounding; When the length of feeder cable between1000m and2000m, with the midpoint grounding; When the length of feeder cable is over2000m, with the cross connection grounding or segmentation protection grounding.After putting into operation, the insulating layer will aging gradually due to the cable itself and the other external factors. If cable insulation aging can be monitored, is extremely important for long-term stable operation of the feeder cable. The propagation characteristics of partial discharge pulses in cable is simulated by PSCAD/EMTDC, choice partial discharge signals in the cable insulation aging test as electrical quantities for monitoring system. Initially put forward the main frame diagram of feeder cable online monitoring based on partial discharge.