Short circuit currents of the SEPTA traction power distribution system

The Southeastern Pennsylvania Transportation Authority (SEPTA), USA, is undertaking a multi-phase modernization program of various electrical and infrastructure facilities. In this effort, a considerable amount of the facilities will be upgraded or replaced. The electrical power supply system is planned to be upgraded with modern state-of-the-art equipment. The overall aim of this effort is to increase the system performance and reliability while maintaining passenger and operator safety. In order to further the implementation of the ongoing modernization program, SEPTA authorized a preliminary engineering study of its electrical system. This effort included a comprehensive set of traction power system load flow studies, voltage drop analyses, short circuit studies, grounding grid analyses for the new substations and protective relay coordination studies. This article discusses the method developed to perform the short-circuit studies. The method is readily adaptable to many different feeder, trolley and track configurations.