Power supply arm protection scheme of high-speed railway based on wide-area current differential

When fault occurs on cross-coupling autotransformer(AT)power supply traction network,the up-line and down-line feeder circuit breakers in the traction substation trip at the same time without selectivity,which leads to an extended power failure.Based on equivalent circuit and Kirchhoff’s current law,the feeder current characteristic in the substation,AT station and sectioning post when T-R fault,F-R fault,and T-F fault occur are analyzed and their expressions are obtained.When the traction power supply system is equipped with wide-area protection measurement and control system,the feeder protection device in each station collects the feeder currents in other two stations through the wide-area protection channel and a wide-area current differential protection scheme based on the feeder current characteristic is proposed.When a short-circuit fault occurs in the power supply arm,all the feeder protection devices in each station receive the feeder currents with time stamp in other two stations.After data synchronous processing and logic judgment,the fault line of the power supply arm can be identified and isolated quickly.The simulation result based on MATLAB/Simulink shows that the power supply arm protection scheme based on wide-area current differential has good fault discrimination ability under different fault positions,transition resistances,and fault types.The verification of measured data shows that the novel protection scheme will not be affected by the special working conditions of the electrical multiple unit(EMU),and reliability,selectivity,and rapidity of relay protection are all improved.

Improved fault location method for AT traction power network based on EMU load test

The autotransformer(AT)neutral current ratio method is widely used for fault location in the AT traction power network.With the development of high-speed electrified railways,a large number of data show that the relation between the AT neutral current ratio and the distance from the beginning of the fault AT section to the fault point(Q-L relation)is mostly nonlinear.Therefore,the linear Q-L relation in the traditional fault location method always leads to large errors.To solve this problem,a large number of load-related current data that can be used to describe the Q-L relation are obtained through the load test of the electric multiple unit(EMU).Thus,an improved fault location method based on the back propagation(BP)neural network is proposed in this paper.On this basis,a comparison between the improved method and the traditional method shows that the maximum absolute error and the average absolute error of the improved method are 0.651 km and 0.334 km lower than those of the traditional method,respectively,which demonstrates that the improved method can effectively eliminate the influence of nonlinear factors and greatly improve the accuracy of fault location for the AT traction power network.Finally,combined with a shortcircuit test,the accuracy of the improved method is verified.

Research on Voltage Losses of AT Traction Power Supply System

Unilateral power supply system has been used because of the management status of the power grid system, while, bilateral power supply system is adopted in the Soviet Union and France. The feasibility that whether bilateral system can be put applied in China is discussed. Compared with unilateral power supply system, bilateral system has better reliability and better capability of supply power system, which gives bilateral system more advantages over unilateral system on both engineering investment and operating efficiency. In this paper, voltage losses under the two different systems are calculated and also compared, the advantages of bilateral system is explored and then conclusion is drawn by referring to the practical data of passenger transport lines.