Modelling, Simulation and Analysis of ac Locomotives for 25 kV ac Railway Traction System - OHE Protection Considerations

摘要

The work presented in this paper addresses the problem encountered by distance relay when protecting 25 kV ac railway traction systems. One of the key features of this paper is the detailed analysis of traction system, dividing into various sub-system, so that each sub-system is studied to its minute details to facilitate modelling as close to the actual system as possible. Modelling, simulation and analysis of ac locomotives have been carried for widely used traction system and its effect on protection of traction overhead equipment (OHE) is also studied. PSCAD is used for generation of test signals for a 25 kV ac single-phase 50 Hz railway traction system. Based on simulations it has been observed that ac locomotives inject significant amount of current harmonics in the primary side. Moreover, change in drive frequency and steady state/dynamic conditions of motor significantly affect the performance of the protective relays. Finally, specific considerations for protection of traction OHE are proposed.