Study On The Mechanism And Influencing Factors Of Insulation Joint Overvoltage In High-speed Railway Station

In 2019,China's total high-speed rail mileage will exceed 30,000 km.One year ahead of schedule to achieve the ambitious goal of the medium-and long-term railway network plan.The construction of such a long distance high-speed railway line means that more high-speed railway stations need be established.Because China has a large population,vast territory and abundant resources,it needs high-speed railway to increase the transportation capacity and improve the transportation efficiency.Therefore,the newly built high-speed railway stations have multiple lanes and the environment is complex.In order to ensure the normal operation of the railway circuit in the station,the mechanical insulation joint will be set up in various places inside the station yard.However,when the train passes through these insulation joints,overvoltage arc phenomenon will occur and the insulation joints will be burnt.In serious cases,even the rail will be burned,which will affect the safety of driving and bring losses to the national economy.Therefore,it is necessary to study the mechanism of over-voltage of insulation joints.First of all,when the transient model of high-speed railway station is established,this paper found that the rail could not and did not need to establish a complete model in the station.Therefore,the electromagnetic transient simulation software ATP-EMTP is used to establish the simulation model of high-speed rail track based on the classical bergeron model.According to the wave process theory,the voltage wave will be reflected at the end of the transmission line when it passes through the transmission line with different wave impedance values.According to this principle,the orbital wave impedance can be calculated by simulation.So when complete high-speed field model is established,the terminal of the track is added with a resistance equal to the value of orbital wave impedance to simulate the infinite length of the track model,thus eliminating the reflection process of the voltage wave at the terminal.Then,a complete high-speed railway station field model is established in this paper to simulate the process of the train passing through the insulation joint.And a simulation analysis of the voltage at both ends of the insulation joint is conducted.The voltage waveforms at both ends of the insulation joint and the current waveforms of the backflow cables on both sides are analyzed.And the generation mechanism of the overvoltage at both ends of the insulation joint when the train passes through the insulation joint is studied qualitatively.It is found that the amplitude and phase of the traction current have a great influence on the insulation joint.The amplitude of the over-voltage of the insulation joint increases with the instantaneous current amplitude of the train passing through the insulation joint.When the train speed is large,its traction current is also large.Although the time it takes to pass through the insulating joint will be reduced,the influence of amplitude increase will be greater.Therefore,the overvoltage amplitude of the insulating joint will also increase with the increase of the train speed.The position of the reflux cable has no significant influence on the overvoltage amplitude of the insulation joint,but it will affect the time when the overvoltage peak of the insulation joint appears.Secondly,the mechanism of impulse current when the train wheelsets pass through two kinds of insulation joints is analyzed theoretically.That is,when the rear wheel pair of the train breaks away from the insulating joint,two shock currents of equal amplitude and opposite direction will be generated on both sides of the insulating joint.According to two different kinds of insulation joints,different transient impact models are established.The impact voltage of two kinds of insulation joints can be expressed by twice of the product of impulse current and impulse impedance,but the impact impedance of different types of insulation joints is different.The corresponding station and field models of two kinds of insulation joints are established by using the electromagnetic transient simulation software ATP-EMTP.The train pass through the above two different types of insulating joint are simulated.The corresponding overvoltage amplitudes of the two types of insulation joints are obtained by simulation.Compared with the calculated theoretical values,the errors are less than 10%,which can be used as an estimation method for engineering assessment of insulation joint overvoltage.At last,the transient overvoltage of the insulation joint connected with the choke rheological neutral point is tested on the spot.It is proved that there exists transient impulse overvoltage which is consistent with the waveform in this paper.The measures that are used to reduce the overvoltage of insulation section are also put forward.