Protection setting in 2x25 kV 50 Hz railway traction systems by digital simulation

In this paper, after a short description of the problems related to the detection of short circuits in 2x25 kV 50 Hz traction systems, a methodology for the choice of the operating area of the relay for protections based on the comparison between a measured line impedance and a fixed minimum impedance is presented. The proposed methodology has been realized through the development of a procedure for the automatic management of the simulation of a given electric system, considering different failure positions and different types of failures. Various software tools have been utilized: -ATP (DOS version of EMTP) for the modelling and simulation of electric networkso; -macroinstruction systems for the management and the automatic editing of files, for the automation of iterative simulations related to different parameters, for a numerical processing of data and for a graphic management of results. Finally, the results obtained for a section of a high speed double track railway system are reported; they refer to a situation in which a neighbouring substation is assumed to be out of order.