Low frequency magnetic protection design of railway signal lines on rail-road bridge

For the economic development and transport demands, various types of rail-road bridges have been widely applied in China. As the high voltage (HV) transmission lines are laid along the road part, once there is a short circuit in the power lines, its electromagnetic disturbance, which mainly composed of low frequency magnetic field disturbance, would induce the longitudinal induction electromotive force (LIEF) higher than the normal operation electromotive force on railway signal lines. This paper builds up a simulation model of rail-road bridge in low frequency magnetic field and simulates the longitudinal induction electromotive force along railway signal lines caused by short circuit current of power lines. The shielding effectiveness of the rail-road bridge has also been studied and simulated. In order to protect the railway signal lines from disturbance, a practical design of cable tray based on low frequency magnetic field shielding theory has been presented and is applied to actual rail-road bridge construction.