Aluminium-alloy conductors for a.c. traction overhead equipment

The paper gives a brief account of the investigation and development work done by the Indian Railways in close collaboration with Indian manufacturers of aluminium conductors and fittings in evolving suitable substitutes of cadmium-copper catenary wire, grooved copper contact wire, copper dropper wires and fittings, as used in the conventional simple polygonal type of 25kV a.c. traction overhead equipment. Two short lengths of the first aluminium-alloy traction overhead equipment have been under service trial on one of the busy main lines between Calcutta and New Delhi for the past six or seven years. Large-scale trial installations on all the zonal Railways equipped with 25kV a.c. traction are in hand. The trial so far conducted shows a promising behaviour of the aluminium alloy as grooved contact (trolley) wire. In fact, if the metal (magnesium-silicon-aluminium alloy) proves its worth in this application, its use in other forms as overhead conductors should have much more chance of success. The next few years´ experience is bound to show whether this new metal would possibly be a good substitute for copper and its alloys for application in a.c. traction overhead equipment, which is light and caters for a comparatively smaller load current at high voltage. Theoretical assessment shows that, under the present-day conditions, the initial cost may be about 10% cheaper than the conventional copper equipment, and life of the aluminium-alloy contact wire could be anything above two-thirds of that of the copper wire. The cost comparison is, however, subject to fluctuations in prices of raw materials and, to some extent, dependent upon traffic density, as well as other factors like cost of labour and use of mechanised equipment for erection etc.