Study On Typical Faults Model & Automatic Switch Unit For Secondary Circuit Of Railway Traction Side Bus

Electrified railways,as an important component of the national comprehensive transportation system,are conducive to promoting the sustained,healthy,and orderly development of the national economy and society.The traction power supply system is a transformation and distribution system that provides electrical energy to electric trains,and the working status of any of its power components will affect the operational safety of the transportation line.During operation,the secondary circuit of the traction side busbar is prone to high-voltage fuse failure induced by rodents.Therefore,it is necessary to use relevant theories and technologies such as temperature field,transient simulation,electrical automation,FPGA,etc.To study an automatic switching device suitable for the secondary circuit of the traction side busbar.Firstly,based on a brief explanation of the composition and power supply characteristics of the traction power supply system,the paper focuses on analyzing the equipment composition,working status,automatic control devices,and voltage transformer wiring forms of the secondary circuit of the power supply system;Based on engineering background and literature,the types and causes of secondary circuit faults were summarized and analyzed,with a focus on analyzing typical faults in the secondary circuit of the traction side bus.Secondly,taking secondary circuit high-voltage fuses as the research object,the melting mechanism of fuses was analyzed using temperature field theory,and a fuse fault feature extraction method based on impedance features was constructed;Build an electromagnetic transient model for single-phase arc grounding fault in the secondary circuit PT based on PSCAD/EMTD electromagnetic simulation platform,combined with engineering parameters;Using Cassie arc algorithm,fuse that can calculate resistance in real-time is added to the fuse model＿Cassie＿Model module to achieve typical fault modeling and early warning analysis of the secondary circuit of the traction side bus.Once again,based on the unmanned and safe operation requirements of the traction substation,an automatic switching device for the secondary circuit voltage transformer of the traction side bus is developed,and the overall design of the voltage switching device is carried out,extending the hardware and software design of the device;In terms of hardware design,it is determined to use plug-in design for four modules: A/D,FPGA,CPU control,and voltage switching outlet.The module plug-in is connected to the inlet of each circuit board motherboard;In software design,the automatic switching logic for voltage mutual protection is written by editing logical equations,and communication schemes and fault recording are designed.Finally,to verify the working performance of the pressure mutual automatic switching device,a pressure mutual switching test environment was established in the laboratory;And real-time monitoring of the data information of the voltage transformer through on-site testing of the device.The experimental results show that the automatic switching device of the traction side bus voltage transformer has achieved the design goal,and the device has advantages such as gradual change in operation and sensitivity,making it very suitable for maintenance work of high-speed railway power supply systems.