Electricity Generation and Supply

Since those exciting early days there has been a tremendous increase in the size and complexity of copper cables, and new and more efficient means of laying, recovering and repairing cables at sea have been developed. Today every continent is linked by a number of lines, some of very intricate construction. On land, in the industrial countries of the world there is everywhere a vast network of both underground and overhead lines, for communications and for the distribution of power; some of these require a number of different materials and a very high degree of protection, usually by serving and sheathing. There are also countless miles of insulated copper wire in use for the distribution of electricity to houses, flats and commercial and industrial buildings.

Copper conductor cables range from the simple insulated pair of wires, which operates a door-bell, up to multi-core cables which may comprise hundreds of separate copper wires. One of the largest standard power cable cores contains 169 copper wires, each 0.107 in. in diameter.

The manufacture of a modern power cable, whether high or low voltage, is extremely complex and involves numerous operations - stranding, insulating, sheathing, armouring. In general, the required number of copper wires is first stranded and then insulated with a covering of paper, rubber, varnished cambric, cotton or plastics. The cores are then twisted together with a suitable lay, the interstices being packed with a filler so as to give the whole an approximately circular cross-section. Sometimes the cable is next given a stout outer sheath of lead or aluminium; and in circumstances where there is a possibility of mechanical damage, the cable may also be armoured with steel armour wires. Certain long cables are also oil- or gas-filled for use at high voltages.*

Modern telephone cables are even more complex and may comprise no fewer than 18 'units', each unit having 101 pairs of copper wires, or 1818 pairs of wires in all.

One way of satisfying the increasing demand for electricity has been by increasing the voltage. In 1890 the first high-voltage underground mains in this country were installed by Ferranti between Deptford and London. Four mains, each about seven miles long, were laid and put into service at 10,000 volts. The conductors in each main consisted of two concentric copper tubes insulated with resin-impregnated paper, the diameter of the inner tube being about o.8 in. and that of the outer one 1.9 in. This project involved nearly 140 tons of copper alone.

A year later, in 1891, the first demonstration of long-distance three-phase high-voltage transmission by means of an overhead line was made in Germany, at the Frankfurt Electrical Exhibition. This installation, which was the forerunner of our present-day high-voltage transmission systems, employed three copper wires supported on porcelain insulators and wooden poles. The line, which was 110 miles long, was used to transmit power from generators at Lauffen on the Neckar to Frankfurt, where it was harnessed to light the Exhibition and to work the exhibits.

The transmission of electricity supply led to the need for central power stations, a fact which was realized very early by both Edison and Lane Fox. In 1881 Edison established in Pearl Street, New York, the first public electric supply station. A year later another was opened in England, in the basement of a house in Holborn Viaduct, London. Edison, whose inventiveness was proverbial, designed electric meters, electric mains, lamp fittings and generators complete for the purpose. By 1882 numerous electric lighting supply companies had been formed; but in Britain a misguided Act of Parliament hindered their progress until 1888, when the Act was amended.

* See C.D.A. Publication No. 56, Copper Cables.