Research On The Influence Of Geomagnetic Storms On ZPW-2000A Track Circuit And The Design Of Monitoring Sensor

In recent years,the development of high speed railway in China is remarkable.With the increasing improvement of train speed in railway system,ZPW-2000A track circuit has also appeared in the station.Track circuit is an important part of high-speed raiway signal control system.Its core devices are widely used in microelectronic technology,which is more sensitive to electromagnetic interference,while the electromagnetic environment tends to be complex and harsh.Geomagnetic storm is a kind of extreme weather disaster.It will cause the severe disturbance of the Earth's magnetic field and result in the Earth Surface Potentials(ESP).ESP and ground together with rail compose a loop.Then geomagnetic induced current(GIC)is produced.If the GIC produced by geomagnetic storms invades the ZPW-2000A track circuit,it will threathen the normal operation of the high-speed railway system.First of all,this paper explores the mechanism of geomagnetic storm,describes the way to invading the ZPW-2000A track circuit and the device--BES(K)choke transformer,and analyzes the influence of GIC on the choke transformer.The calculation method of ESP is given and the GIC amplitude is reached to 5A using the Matlab software according to the flow path of GIC in the track circuit.Secondly,the finite element model of choke transformer is built using Ansoft Maxwell to obtained the exciting current,flux linkage,inductance,magnetic flux density,core loss and winding loss of choke transformer.The results show that the 2A GIC makes the transformer begin to saturate,the excitation current has a sharp peak wave and the distortion rate of the primary side current increases,which cause the decrease of self inductance of the winding.Meanwhile,the GIC flowing into the choke transformer will increase the flux and magnetic density of the transformer core and make it work in a saturated state.When the GIC amplitude is 8A,the core loss will increase byl.2times and the winding loss will increase by 4.8 times.The simulation of transformer air gap is 0.1mm?0.6mm and the GIC amplitude of transformer is 8A.The simulation results of excitation current,magnetic flux density,iron loss,copper loss and inductance are obtained.The results show that proper air gap can effectively improve the saturation current of transformer and reduce the distortion of excitation current,and reduce magnetic flux density and loss.However,because the air gap will lead to the decrease of inductance,the length of air gap can not be too large.It is concluded by calculation that the impedance of the frequency shift signal can not meet the requirement of 17? when the equivalent excitation inductance of the transformer is less than 1.6mH and the transformer gas gap is 0.4mm.It is proved that the air gap of the transformer will lead to the decrease of the impedance of the frequency shift signal,which leads to the loss of the pressure drop of the track relay.Therefore,an equivalent circuit model of a new BES(K)choke transformer is established in this paper.According to the secondary winding inductors obtained from the simulation,the suitable matching parameters are calculated and the equivalent circuit model of the transformer is simulated on the Multisim platform.The results show that the frequency shift impedance of the BES(K)choke transformer with the adapter increases to more than 17 ?,and the power frequency impedance of the transformer decreases.The exciting current of BES(K)choke transformer equipped with adapter is reduced by 111.2 times than that of the choke transformer without adapter,and the disturbance voltage and interference power of the traction coil are significantly reduced by 49.3 times.Finally,a new GIC monitoring device,a current sensor based on giant magnetoresistance effect,is designed in this paper.The current sensor device consists of a GMR sensor of range of 100 A and equipped with magnetic flux guide.This paper discusses the influence of the extreme deflection angle and horizontal offset betweem the sensor and the conductor on the measurement of the sensor,and the simulation is analyzed by theoretical derivation and finite element method(FEM).The simulation results show that the measurement error is less than 3.66%.When the horizontal offset is controlled within 16mm and the measurement error is less than 6.62%when the angle deflection is controlled within 70°.The sensitivity is improved by19.7 times and the measurement error is reduced by up to 121 times at extreme position.In this paper,the GIC monitoring current sensor with two forms of open loop and closed loop is designed,and the signal conditioning circuit of the monitoring device is designed.The model is built by Multisim simulation software,and the performance of the design circuit is verified by simulation analysis.Finally,the Ansoft Maxwell is used to simulate the closed loop giant magnetoresistance sensor.When the winding ampere-turns of feedback of the GMR sensor is equal to that of current measured,the closed loop sensor operates at zero magnetic flux state,which proves the working principle of the"magnetic balance" of the closed loop sensor.