Modeling Indirect Lightning Strikes for Railway Systems With Lumped Components and Nonlinear Effects

Induced voltages due to lightning strikes along multiconductor transmission line (MTL) systems terminated with different loads at line ends have been widely studied by solving telegraphers´ equations using the finite-difference time-domain method. However, MTL systems with lumped series and shunt-connected devices/components along the lines have not attracted much attention. There are methods available for introducing lumped components along MTL systems. In this paper, a method previously developed by the authors will be used to determine induced voltages across transformers connected to the catenary wire and track-circuit relay units along the MTL system representative of a Swedish single-track railway system for the case of indirect lightning strikes. Nonlinearities like soil ionization and insulator flashovers are also considered. It is found that both the nonlinearities and lumped components together dominate the induced-voltage amplitude and wave shapes across devices/components.