Whole system compatibility measurements of the autotransformer supplied 50 kV railway in New Zealand

New Zealand Railway Corporation (NZRC) have completed the electrification of the central section of the North Island Main Trunk (NIMT) and electrified commercial operation began in 1988. Because of the many novel features of this railway electrification, Hawker Siddeley Rail Projects (HSRP) were required to undertake a detailed compatibility study of all electrical sub-systems by NZRC, at the design stage. During the design process, new computer based methods of analysing the effects of loco operation on low power signalling and telecommunication circuits, as well as on the Electrocorp power system, were developed at the University of Birmingham. The simulator developed was used to confirm design choices relating to telecommunication cable earthing, the degree of electromagnetic screening which could be realistically achieved and the likely values of rail to earth voltages in the nominally earth insulated traction supply system. The authors discuss the EMC requirements and the test programme. The results for signalling, a locomotive, a substation and the telecommunication cables are given