Study On Mechanism Of Wrong-phase Short-circuit Of Catenary Based On Over-phase Mode Of On-column Switch

The single-phase power frequency traction power supply system is used in the electrified railway in China.When the EMU passes by,a large amount of negative sequence current will be injected into the system.In order to maintain the balance between the external power system three-phase load,reduce the influence of negative sequence current on the power network,and improve the capacity utilization and reliability of the power supply equipment,the traction power supply system of our country adopts the power supply mode of rotating phase sequence and stratified and partitioned power supply.In the domestic AC electrified railway power supply system,the electric phase is usually set at the outlet of the traction substation and the end of the power supply arm,and the power supply is supplied by different phases on the left and right sides of the power supply system.Electric phase separation not only ensures the mechanical connection of catenary and maintains the stability of pantograph-catenary relationship,but also isolates the left and right phases,which leads to the electric separation becoming one of the weak links in the traction power supply system.When the main circuit breaker of the EMU does not jump through the electric phase separation,it is easy to produce the arcing of the pantograph,which leads to the abnormal short-circuit fault of the traction power supply system,but the abnormal short-circuit fault of the catenary is a kind of short-circuit fault with great destructive force.The corresponding relay protection scheme must be considered.A large number of literature studies show that the arcing phenomenon of pantograph is closely related to the structure of joint electrical phase separation of anchor segment.By changing the electrical structure of the joint type of anchor and combining with the reasonable switching control strategy,this paper presents an automatic phase crossing technique based on on-off switch.While avoiding the arcing of the pantograph and eliminating the dead zone of the electric power supply,the technology has the advantages of simple structure and low cost.It is convenient to maintain and can minimize the time of power loss when the EMU is out of phase.Secondly,the traction power supply system is modeled and theoretically calculated on the basis of the actual line parameters from the friendship substation of Panying high-speed line to the power supply section of the West fourth Substation(referred to as the Yuci Power supply Section).Then the accurate simulation model of traction power supply system is built by using Matlab/Simulink software.The transient process and electrical parameters of the EMU are simulated under different loads and the feasibility and applicability of the technology are verified.Finally,fault mechanism analysis and short-circuit current calculation of catenary abnormal short circuit based on over-phase technology of on-column switch are carried out,and three-stage over-current protection is put forward as the main protection scheme of catenary abnormal short-circuit fault.The simulation model of traction power supply system based on Matlab/Simulink software is used to simulate the off-phase short circuit of catenary based on the technology of over-phase switch on the post,which verifies the correctness and feasibility of the relay protection scheme.