Development of power supply and supervisory equipment for British Railways 50 Hz a.c. electrification

Cost considerations have been a major factor in the developments which have taken place in BR´s 50 Hz a.c. electrification since 1960. The first efforts towards cost reduction were directed towards the more economical application of established techniques and included the elimination of brick buildings to house ancillary equipment and the use of switchgear in a steel housing with bare overhead connections to the contact system. Subsequently, the development of the vacuum interrupter was seen to offer prospects for still greater economy in switchgear, and a design of great simplicity has been developed in which the vacuum-interrupter circuit breakers and all ancillaries are housed in one modular enclosure. 144 vacuum-interrupter 25 kV single-pole single-phase circuit breakers are now on order. Advantage has been taken of developments in solid-state devices to develop faster protection for track feeders and to apply a supervisory system of the continuously scanning type in which the wear and tear associated with electromagnetic devices is minimal. The basic principles are given. It continues to be necessary to suppress inductive interference at source and established methods are used. The harmonics generated by the rectifiers on the motive-power units are a matter affecting the power-supply network, and information is given concerning the magnitude of these. A table of costs applicable to the beginning, the middle and the end of the period shows that they have been held down in spite of inflation.