Study Of Multi-source Signal Response And Grounding Effect Of Integrated Grounding System For High-speed Railway

The Integrated Grounding System(IGS)is a special grounding system of high speed railway,and it is an important guarantee for the safe operation of high-speed railway.The IGS not only provides an equal potential grounding platform for all kinds of "strong and weak power systems",but also provides a return path for the normal operation of traction return current,and it also provides a good powder flow pathways for the traction short-circuit current and lightning current.There is a large difference in the amplitude and the harmonic content of the current flowing through the connecting ground wire(CGW)of the IGS.As a common connecting point,the response characteristics of all kinds of current signals must be different in the IGS.There is also a large difference in the characteristics of the IGS when it is motivated by various signals,such as grounding impedance,dissipation rule,and distribution characteristic and so on.To study the characteristics of different signals in the IGS and the difference of the response characteristics of the system is contributed to establish a more accurate simulation model.And it can also provide the basis for the analysis of the potential distribution of the IGS under different signals,furthermore provide the precondition for the safety analysis of the power supply and signal equipment.In this paper,firstly,a distributed parameter model of the CGW is established based on the propagation characteristics of the traction return current in the IGS.The equivalent harmonic impedance calculation method is using to reflect the skin effect on the CGW.When traction return current flows far from the grounding grid,it is found that the current is a significant attenuation trend along CGW,and the attenuation length is about 100 m.At the same time,along with the decrease of soil resistivity,the increase of grounding wire radius and buried depth and length,the equivalent resistance is reduced.When traction return flows near from the grounding grid,it is found that the grounding grid is the main transmission route of the traction current,and the equivalent resistance of the grounding grid is very stable.Furthermore,the situation of the system of the IGS is analyzed.The effective discharge length of earth wire is about 120 m when the short circuit current flows far from of the grounding grid.When traction current return flows near from of the grounding grid,it is found that the equivalent resistance of the grounding grid is also very stable.Then,the lightning characteristic model of IGS`s CGW is established.In view of the characteristic of high lightning current amplitude,the influence of spark discharge on the response characteristic of the CGW is analyzed.And the area range of the spark discharge through the ground wire and the effective length of the flow are obtained.At the same time,the influence of the lightning current amplitude,the wave head,the soil resistivity and the length of the ground wire on the impedance is analyzed in the frequency domain,it is found that the low frequency equivalent impedance of the CGW is stable,and the high frequency impedance is influenced by various factors.In addition,the three-dimensional structure of the IGS is constructed by using CDEGS software.And the impact characteristics and the flow pattern of the main discharge part of the CGW,PW line and the pillar foundation are analyzed in this paper.Finally,two evaluation indexes are established,which are ?the shunt coefficient? and "the equivalent resistance of the CGW".The influence of PW on the shunt coefficient and ?Rail--CGW inductance? effect on the equivalent resistance of the CGW are considered.The mathematical expressions of the two indexes are derived and verified by the measured data.The results show that the index can accurately evaluate the grounding effect of the IGS,at the same time the index reduced the error evaluation of the IGS for bridge section and tunnel section.