Development of overhead equipment for British Railways 50Hz a.c. electrification since 1960

An account is given of the development of overhead equipment for use on British Railways electrification schemes during the period 1960¿1970. These developments have led to equipment having improved dynamic performance and lower cost. Concurrently, the efficiency of installation has been increased. Economies have followed the disappearance of steam locomotives, allowing the use of less expensive materials for metal fittings and insulators. Other improvements have arisen from steady development and the application of new techniques. Dynamic performance has been improved by the use of sagged simple-catenary equipment, damping of the pantographs and optimisation of span profiles, dropper spacings etc. Cadmium-copper conductors have in nearly all cases, been replaced by hard-drawn copper or by steel-reinforced aluminium. Supporting structures have been simplified, and sometimes replaced by headspans, and tensioning and anchoring arrangements have been improved. Resin-bonded glass-fibre arms combining the functions of spring support and insulator have been used to improve tunnel equipment, and many other improved insulators using glass fibre and other materials have been developed. By careful attention to detail, the multiplicity of individual components has been reduced to a much smaller number of interchangeable components. Bonding techniques have been improved, and bonding has been simplified. Economics have been achieved by detailed planning and co-ordination of constuction and operating activities.