Economic aspects of overhead equipment for d.c. railway electrification

Abstract

A careful examination is made of many factors affecting the cost of overhead equipment, taking the 0.75 in2 Liverpool Street-Shenfield type as a standard.Figures are quoted to show that considerable economies can be achieved by making reasonable track alterations in junctions and yards, wherever possible, to permit the use of light short-span structures.Present practice in Britain is examined; while still ensuring safety and reliability, modifications to achieve economies are recommended, including reduced wind loading, increased stress in steel, reduced minimum thickness of steel, smaller and less costly foundations, longer spans between structures on open lines, spliced catenaries between stations, crossed contact wires, cap and pin insulation, simpler droppers and rail bonds of smaller copper section.Other possible economies mentioned include reduction of copper section to 0.6 in2, use of bare feeders, reduced switching and sectioning, span-wire registration, and the use in certain circumstances of tubular steel and pre-stressed concrete structures. Economies not recommended include less effective cleaning of steel before painting, simplecatenary construction, copper instead of cadmium-copper contact wire on main lines, and ferrous fittings on live equipment.Finally it is shown that careful advance planning, completion of all survey and civil engineering work well ahead of overhead-line construction, and a steady programme of work will produce additional economies amounting to a high proportion of the total of all other recommended economies.