A review of the use of medium voltage polymeric cables for the distribution of AC power supplies to British Rail DC electrification substations

British Rail direct current electrification systems cover about 1800 route km of railway track in the south east of England and 170 route km in the area around Liverpool. The top contact third rail conductor system used is energised at a nominal voltage of up to 750 V DC supplied from trackside rectifier substations spaced at 4 to 7 km intervals. Generally, three phase 50 Hz power supplies are taken from the Regional Electricity Companies (RECs) at 33 kV or 11 kV and distributed via a trackside cable route to the substations so that, normally, each location is able to be supplied from at least two sources. Recent electrification schemes use subdistribution of 33 kV at a voltage of 11 or 22 kV. Typically, a REC will supply up to 6 substations, or 12 under abnormal conditions