Study on Compenstation of Capacity Currents of 10 kV Railway Continuous Power Transmission Lines

10 kV continuous power transmission lines are widely used for power supply of railway stations.The continuous power transmission lines are erected along the railway lines and mainly constructed of the overhead type.A small part of such transmission lines are cables radiating from substations.In recent years,in order to improve the reliability of power supply,the cable percentage is going up and even some continuous power transmission lines are wholly cable lines.As a result,the ground capacitance current increases remarkably so that the ground-fault arc can not be extinguished by itself.This reduces the instant-fault self-removing ability of the neutral-ungrounded system.Wye-connected reactors with neutral-grounding are generally used to compensate the capacitance currents of the continuous power transmission lines.Our study shows that,with the 0.75 compensation ratio,the total ground-fault current in such systems may be so heavy that the ground-fault arc would not be extinguished by itself.It is proposed that compensation should be aimed at self-extinction of the ground-fault arc.A computational method for choosing the optimum compensation ratio to guarantee the ground-fault arc self-extinction is put forward.A case study is given to verify the proposed method.