Research On Electromagnetic Effect From Integrated Grounding And AT Power Supply System To Signal Cable

Signal cable is one of the important channels of information transmission,which provides an important guarantee for the safety of railway transportation.With the development of railway technology and the increasing of the locomotive speed,the traction current in the power supply network is greatly increased,and the interference becomes more serious.AT power supply technology improves the symmetry of power supply network,so as to improve the electromagnetic environment around the line.The integrated grounding technology provides an equipotential connection for each specialty,which reduces the influence of the potential difference between different systems,so that the electromagnetic interference of the signal cable is reduced.With using these technologies,the impact of the signal cable is reduced to a certain extent,but it is not completely resolved.Therefore,the research on the impact of the signal cable is still an important areas.Firstly,the influence factors of signal cable is analyzed.AT power system reduces the asymmetry of traction current,but it is mainly used in high speed and heavy haul railway,the traction current is strong.The integrated grounding technology reduces the influence which caused by different professional potential difference,but its ground wire is connected with the AT power supply system,the traction circuit will pass on it.And the line is mainly adopted elevated lines,the distance between signal cables and grounding is close because of the limited condition.These factors are harmful for the electromagnetic protection of the signal cable.Secondly,according to the relationship between the AT power supply system,the integrated grounding system and the signal cable,an integrated model is established in the paper.The equivalent model is found by node voltage method and ‘F' lumped parameter form,and the calculation method of model parameters is given.Thirdly,the electromagnetic effects of the signal cable is analyzed and calculated under the normal condition.The traction current of 1km length signal cable is calculated under the condition of single or double ended grounding.And the induced electromotive force is calculated by using the formula of calculating electromagnetic effect.It is concluded that the single ended grounding is better than the double ended grounding in reducing the electromotive force.In order to understand the electromagnetic effects of signal cable more comprehensively,various factors are analyzed.The induced electromotive force of the signal cable is calculated in different factors,such as the length of the signal cable,the running position of the locomotive,the electric conductivity of the earth and the distance between the ground wire and the signal cable.Some conclusions are drawn by comparing with the specification limits,and technical measures for improving electromagnetic protection of signal cable are summarized.