《A review of 25kV A.C. single-phase railway traction supplies.》.pdf

Revision date: 24-06-2010. Page 1 of 38 Power To The Pantograph. A review of 25kV A.C. single-phase railway traction supplies. By H. G. Reading, BSc. (Hons.), C. Eng., M.I.E.T., formerly System Development Engineer, United Utilities. You are welcome to use material from this technical paper and accompanying slide presentation, but please be courteous and acknowledge its source. Thank you from Howard Reading. UU file path: S:\GP System Development\Project Files\Network Rail\Rail Safety and Standards Board\Lecture\Power to the Pantograph.doc HGR file path: C:\Documents and Settings\Howard\My Documents\Presentations\Power to the Pantograph\Power to the Pantograph, illustrated..doc C:\Downloads\Copy of Power_to_the_Pantograph,_illustrated..doc Revision date: 24-06-2010. Page 2 of 38 SYNOPSIS This paper aims to explain the fundamental theory of the electrification of Britain’s railways. Firstly, “Classical,” 25kV traction supplies are set in the railway context. Constraints imposed by signalling, earthing and the control of earth return current are discussed. At the traction supply point negative phase sequence (NPS) and harmonic voltage issues are key factors. The design fault-level of the 25kV system determines the impedance of the traction transformer. Finally, the newer auto-transformer supply system is explained and contrasted with the, “Classical,” 25kV system. There is an accompanying slide presentation illustrating many of the topics covered in th