| In recent years,with the rapid development of electrified railway technology in China,high-speed rail has gradually become the preferred means of transportation for passenger and freight transportation in people’s daily life due to its advantages of speed and comfort.At the same time,the construction of “four horizontal and four vertical” railways in China is of great significance to China’s economic development,especially to the implementation of the strategy of the western development.This puts higher requirements on the safe and effective power supply of the electrified railway power supply system.Oil-immersed inverted current transformer installed in electrified railway power supply system has the function of protection and detection.Its safe and reliable operation is related to the safety and reliability of traction power supply system.Most of the damages and faults of high voltage current transformers are caused by insulation damage.The state of insulation material is closely related to the electrical life of insulation.The material properties of oil-paper insulation in current transformer are affected by many factors,such as environmental temperature,chemical composition of a single medium,different structure of insulation system,etc.The change of the material properties will affect the complex dielectric constant and dielectric loss factor of insulation.The results show that moisture content,temperature and applied electric field frequency have the greatest influence on dielectric parameters of insulating materials,and also determine the insulation characteristics of insulating materials.The current transformer used in traction power supply system is not only affected by its complex external climate environment,but also by the voltage fluctuation and harmonic resonance caused by the traction load of electrified railway,which causes serious harmonic pollution in the power grid.According to the investigation and research,the main fault reason of current transformer is the main insulation breakdown.Therefore,it is particularly important to study the influence of complex environment on the insulation material of current transformer and the transient voltage impact of electrified railway on current transformer during operation.In order to study the influence of complex conditions on the performance of current transformer insulation materials,the dielectric parameters of various insulation materials were measured at different temperatures(-50℃~180℃),different humidities(<10%),different voltage shocks and different frequencies(0.01Hz~10MHz).The traction power supply system of oil-immersed inverted current transformer is modeled,and the transient voltage impact of electrified railway operation on current transformer is studied.The current transformer and its traction power supply system are modeled by combining theoretical analysis with numerical simulation.According to the working principle of each component of traction power supply system,the numerical model of current transformer-traction network-EMU based on simulink simulation is established.The equivalent circuit model of traction network in traction power supply system is established after reducing the order of traction network.With the help of electrical theory and uniform transmission line theory,the factors affecting the transient voltage impulse of current transformer in power supply system are analyzed and verified by simulation.The super-phase process of the EMU is analyzed,and the simulation model of the phase separation process is established,and the simulation results are analyzed. |
