Analysis Of Ground-laid Traction Network Protective Wire And Research On Its Influence On Track Signal Equipment

With the development and construction of high-speed railways in Western China,the impact of strong wind on the traction network has become a serious safety hazard,affecting the safe operation of trains.The protection wire is an important part of the traction network,which has a slender and flexible structure.It is easy to produce large vibration by wind,causing short-circuit or fatigue disconnection of the traction network.The ground-laid protection wire(layed underground)is a protection scheme to reduce the impact of strong wind on the traction network,which has certain engineering practical value for the protection of electrified railways in strong wind areas.However,the ground-laid protection wire will inevitably cause the change of traction return current,which will affect the electromagnetic field generated by the traction network.Therefore,on the basis of the fully parallel AT(autotransformer)power supply traction network,this thesis studies the influence of ground-laid protection wire on the traction return current,the power frequency electromagnetic field distribution in traction network space and the trackside signal equipment under the normal working condition and the short circuit fault condition of traction network along the railway.The main work of this thesis is as follows:(1)The impact of the ground-laid protection wire on the traction return current distribution is studied.The Multi-conductor Transmission Line theory is adopted to establish the equivalent link model of the traction power supply system.And the current distribution of each conductor while the protection wire is overhead and laid on the ground is calculated and analyzed under the normal working condition and the short circuit fault condition of the traction network in the subgrade,viaduct and station four line parallel section.Then the distribution proportion of traction return current on rail,protection wire and through-ground wire is compared,and the change of the traction return current distribution in the traction network of different sections after the protection wire is laid on the ground is obtained.The equivalent link model of the traction network is verified by quoting the measured datas.(2)The impact of the ground-laid protection wire on the power frequency electromagnetic field distribution of the traction network is studied.The Ansys Maxwell is used to establish the traction network model of subgrade,viaduct and station four-line parallel section,and the power frequency electromagnetic field distribution of the traction network is obtained while protection wire is overhead and laid on the ground under the normal working condition and the short-circuit fault condition.The analysis shows that the protection wire laid on the ground increases the electromagnetic field strength in signal cable trough.And the measured data of the power frequency electromagnetic field in traction network space is obtained through the field test,and the simulation calculation results are compared to verify the reliability of the traction network simulation calculation model.(3)In view of the problem of laying the ground-laid protection wire and the signal cable in the same slot,the electromagnetic influence of the protection wire on the trackside signal cable is studied.Using the calculation formula of the induced electromotive force generated by the interference current on the cable core wire,the magnitude of the longitudinal induced electromotive force generated by the magnetic induction coupling of the adjacent rail,the ground-laid protection wire and the through-ground wire on the signal cable while protection wire is overhead and laid on the ground is calculated,and the analysis shows that the protection wire laid on the ground increases the longitudinal induced electromotive force.Furthermore,the influence of the position of the ground-laid protection wire and the size of the comprehensive shielding coefficient on the longitudinal induced electromotive force is analyzed in detail,and the relationship among them is obtained.Finally,the protection suggestions for signal cables are given.