Investigation of grounding resistance effect on the MV grid of Hellenic electromotive railway during lightning strikes

The paper discusses the effect of the grounding resistance on the transient response of MV railway grid during lightning strikes. For study purposes were modelled the electrified railway MV grid (ERMV) that the Hellenic electromotive suburban railway makes use, including the masts, consoles, the rails and the overhead medium-voltage transmission grid of 25kV dedicated for this purpose. For the simulation of the understudied model time-domain solver was adopted in ATP-EMTP software. The model Volt-Time Curve is used for the modeling of the insulator, but it was necessary to create a new equation for the specific model, because of the short length of the insulator in such projects. Two types of lightning are used for the simulation purposes, for fast and slow signal, with current value in 100kA and one measurement in 30kA. For fast signal, the values of front and tail time are 1.2/50μs and for the slow signal 10/350μs. In addition, for the ground resistance: 10Ω, 70Ω and 245Ω are used.