Relay Protection Research For Railway Cable Continuous Power Line

Due to a series of advantages of the cable lines used in the city power grid, power line along the railway also try to use the whole cable model. When the all cable line be used to deliver power along the railway, cable-to-ground capacitance current will be several times the overhead line route, resulting in single-phase ground fault arc is difficult to extinguish, in particular, because of power line along the railway through a long distance, the problem is more serious than overhand line route, so it is necessary to study the system neutral connecting the grounding and relay protection style of the whole cable line along the railway; At the beginning of using cable in city power grid, many believe that cable fault necessarily permanent, but in practice running of cable in the city distribution network found that cable fault to a greet degree is a transient failure. So it necessary to put into reclose and automatic backup power switch-on to improve the reliability of the railway power supply.Firstly, this paper based on the compare of connecting style of the system neutral and grounding of the distribution substation, and contacting the feature of power continuous line of the railway, come up with adopting the low resistance style to connect neutral with grounding. Also this paper makes lots of analysis to single-phase fault of the whole cable line which system neutral point use low resistance connecting with grounding, and found EMTDC modeling. Connecting simulation date this paper make configuration of protection, and make calculation to the whole cable line along the railway.Secondly, since the cable line equivalent capacitance of per unit length is too larger, when single-phase fault circuit happening, non-fault phase cable line capacitance will store many lots of electric field energy which made non-fault phase remaining high voltage for a long time, and leading to great threat to the safe of people and equipment. So it's necessary to analyze the relationship between residual and the over-voltage, studying the feasibility of reclosing operation and the factors of affecting over-voltage of reclosing operation. According to fault-circuit when the cable lines occurs single phase short trouble, analyzing the effecting to cable and transformer.Finally, if reclosing which applied to the cable line is feasible, in addition to using automatic reclosing to improve the reliability of power supply, spare power automatic switching can also be put to restore the power of continuous line, but must pay attention to spare power automatic switching and re-closing equipment matching logic.