Abstract:Research purposes:For the 10kV power transmission line for the ordinary railway in China, the mode of overhead line as main line with cable as auxiliary line has been adopted for a long time without neutral point earthing. For the high-speed railway, the 10kV power transmission line is mainly cable line. Considering the capacitive current of long distance cable line is much greater than the overhead line, and the 10kV cable line is laid together with communication and signaling cables for long distance, thus it is necessary to do the comprehensive study on the earthing mode of neutral point in order to present a proper earthing mode of neutral point of the 10kV all-cable power transmission line for high-speed railway for providing the reference to the similar works.
Research conclusions:Under condition that the voltage of 10kV all-cable power transmission line is regulated by voltage regulator, it is appropriate to use the low -resistance earthing mode whereas the capacity of voltage regulator is lower than 250kVA, the neutral point can be grounded directly. The value of low resistance should be determined by the earthing fault instantaneous tripping mode when single phase earthing current is less than 400A. The value of the earthing grid of substation and power distribution substation should be no more than 1Ω.
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