Study On Novel Protective Schemes Of Traction Power Supply Systems For High Speed Railways

High Speed Railway (HSR) is not new in the world, but it is planed out at present in China. It is certain that HSR will be constructed in China in the near future. As a start of Chinese HSR construction, the Qinhuangdao-Shenyang high-speed railway special for passenger transport has been constructed. The Middle and Long Term Plan of Chinese Railway Network describes that: High-speed passenger-transport lines (HSPTL) between provincial capitals as well as large or middle cities should be built, and four HSPTLs across China from eastern to western side and four HSPTLs from southern to northern side as well as three high-speed passenger-transport systems between cities are to be constructed before 2020.The experiences from regular speed railway indicates that the fault ratios of power supply networks and traction transformers in China are higher than other countries and the wrong operation of protective devices often occurs in Chinese power supply systems by reason of the technical and management levels. The foreign advanced techniques can certainly be adopted to service Chinese railway, but the dependence on foreign techniques can not satisfy our needs for railway transport, especially HSR transport. The purpose of this paper is to systematically study the protective principles of feeder and transformer in traction power supply systems of HSR and to resolve some technical problems for the construction of Chinese HSR and to improve the present protective principles, its functions and reliability.On the basis of analyzing the load characteristics, fault features of traction power supply systems, and the operation behaviors of conventional feeder protection, three novel protective principles are proposed. They are three-zone adaptive distance protective principle and adaptive current increment protective principle which are automatically adjusted by total harmonic ratio (THR) in feeder current, as well as adaptive voltage increment protective principle for wrong-phase fault automatically controlled by THR in wrong-phase fault voltage. The results of field operation and digital simulations indicate the correctness of these principles.The coupling voltage characteristics for transient and permanent faults indouble-end fed electric railway are analyzed in detail. As the fault occurs, the voltage of faulted feeder is determined by the electrostatic and electromagnetic coupling from the un-faulted feeder. In the case of transient fault, the steady voltage includes the voltage due to capacitive and inductive coupling. In the case of permanent fault, the steady voltage includes the inductive coupling voltage only. Based on the coupling voltage characteristics, a novel coupling-voltage-based adaptive fault identification principle is presented. The simulation results show the high identifying sensitivity to transient and permanent faults.The optimal operation equation for impedance match balanced transformer is studied. For every three-phase to two-phase or four-phase balanced transformer, except impedance match balanced transformer, the same transformation relation between primary and secondary currents is proved. This conclusion is important to study and manage differential protection of three-phase to two-phase or four-phase balanced transformer. To provide theoretical basis for management department, the setting rules are systematically studied and the setting formula are given also.By analyzing the impact of capacitor discharge on operation behavior of differential protection and its mal-operation caused by external factor, the disadvantages of differential protection are discussed. The voltage-balanced equations are proposed for two particular connection transformers - SCOTT and impedance match balanced transformers. Based on the voltage-balanced equations, a novel protective principle, and its operation characteristic and operation equation are proposed, and the setting rules and formula are obtained. As an example, the simulation test is carried out for a 75MVA SCOTT balanced transformer. The simulation results prove that...