Читать книгу Central-Station Electric Lighting - Killingworth Hedges - Страница 8

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Uncontrolled financial speculation, aided by the stringent clauses of the Electric Lighting Act of 1882, have been a great deterrent to the extension of old or the introduction of new schemes for the supply of electricity to the public in the same manner as gas. The President of the Board of Trade, replying to a question in the House of Commons, said that, “since the passing of the Electric Lighting Act of 1882, fifty-nine provisional orders and five licences had been granted to companies, and fifteen provisional orders and two licences to local authorities. He was not aware that, in any single case where these powers had been obtained, they had been exercised.” Up to the present time no company supplying electricity has been under the necessity of applying for compulsory powers, and has either obtained permission from the local authorities to take up the streets, or has carried the electric mains over the houses, and, regardless of the question of overhead wires, has depended on wayleaves granted by the too-confiding householder, who has no idea that his roof is supporting a cable weighing 1¾ tons to the mile.

An amendment of the Act of 1882 has passed both Houses without hindrance, and has received the Royal assent. It provides that in the case of Provisional Orders the period after which the undertaking may be bought up by the Local Authority shall be extended from twenty-one to forty-two years, and that portion of the previous Act which referred to the compulsory purchase of the undertaking by a local authority at the end of the term has been altered, and more favourable terms given to the electric companies.

On the Continent, and in the United States, where each city may be said to legislate for itself in matters relating to the general welfare of its citizens, the electric lighting industry is in a very different position, and central-stations are either established or about to be started in every important town. There were, in 1887, 121 Edison central-stations alone, supplying over 323,000 incandescent lamps, and paying dividends from 6 to 14 per cent. The Westinghouse Company, who use a transformer system which is a modification of the Goulard and Gibbs, have a hundred stations, maintaining 191,000 lamps, although the first Westinghouse plant was put down only three years ago. The progress in the United States is so rapid, and there are so many successful applications of central-station lighting, that the subject becomes too large to be even summarised, so that it is proposed to treat in the following pages with some of the principal installations on the Continent and at home.

Travellers abroad are accustomed to find electric lighting installed in the most out-of-the-way places, especially in Switzerland, where water power is abundant and is utilised to generate electricity, so that in small hamlets arc lighting is often employed, and the visitors to the local hotel will find it lit throughout by electricity. Electric light stations in England are, with one exception, small in comparison with those on the Continent. The most important is that at the Grosvenor Gallery, London, which has increased from small beginnings until it now supplies 20,000 glow lamps on sixteen circuits, the total length of which is seventy miles. The next largest, which have been in practical work for some time, are the Brighton and Eastbourne stations, from which small installations of glow and arc lights are maintained in various districts of the two towns. That the question of cost or trouble, and the annoyance of machinery when erected in a dwelling-house, do not altogether prevent the adoption of a superior light, is clearly proved by the increasing number of householders, who, after waiting in vain for electricity to be brought to their doors, have set up the plant necessary to produce it themselves, and find no practical difficulty in doing so. There are also many important public works where electric light has been exclusively adopted. For instance, at the Tilbury Docks there are 1350 glow and 80 arc lamps, distributed over an area of 300 acres, and including the lighting of an hotel, dock sheds, warehouse, signal-boxes, and offices. The London, Chatham, and Dover station at Victoria has also been electrically lighted for the past three years, the current being obtained from a central-station, which was erected for the purpose of supplying electricity to the Victoria district, and for which a provisional order was obtained. This, however, has since been abandoned, although £16,000 had been expended on plant and buildings by the promoters, who preferred to postpone the scheme rather than to submit to the onerous 27th clause of the Electric Lighting Act. Another still larger installation has been put down to supply electricity to the Paddington station and district of the Great Western Railway, as far as Westbourne Park. It embraces an area of sixty-seven acres, and is lighted by 4115 glow and 98 arc lamps. The system adopted is that designed by Mr. J. E. Gordon, and has now been successfully worked for some time; but the many accessories which are introduced, such as telephones, telegraphs, and indicators, make it complicated in comparison with gas, or even with the ordinary electric light systems. The current is generated by two dynamos, each weighing 45 tons, and having revolving magnet wheels 9 feet 8 inches in diameter, 22 tons in weight, a third machine being kept in reserve. These dynamos are separately excited, and produce alternating currents. The electricity is led to a large switch-board for distribution throughout the district by means of five sub-stations; and from this board there branches a double system of mains, which run everywhere side by side, one-half the mains being connected to the first machine and one-half to the second, so forming an excellent arrangement for the prevention of total extinction of the light. The mains running to the sub-stations are on the divided system, which is introduced for the purpose of saving copper, as in a solid cable the loss of pressure is greatest when the full number of lamps is on, and decreases as the lamps are extinguished. With the divided main system it is intended to follow out Sir William Thomson’s formula, which equates the value of the loss of head, and the interest on the saving on the copper. If for a certain main this formula shows that a fall of 20 per cent. is the most economical condition for working, then, since by the divided main the pressure can be kept within a variation of 2 per cent. at the distant end, it follows that a considerable saving can be effected over an ordinary solid main. Special arrangements are adopted at Paddington to keep the pressure constant, a fall of potential being allowed for; thus at the engine-house the pressure is 150 volts, in the passenger station it is 120 volts, and at Westbourne Park it is 100 volts. The arc lamps are fed by the same mains, and are arranged two in series.

A small installation at Kensington Court, erected two years ago, for the purpose of supplying the houses in the immediate neighbourhood, has rapidly developed, and underground mains have been led in many directions from the station, and a constant service of electricity is provided for by means of secondary batteries. As this is the first practical exposition of the secondary batteries’ system of distribution, it is proposed to describe the installation under that head. Central-stations are also at work in Liverpool, Leamington, Taunton, Exeter, and there are also five large installations nearly completed in London, besides the Kensington Court station, all of which will probably be in full swing before the end of the year.

Electric Lighting from Central-Stations is now practically carried out on five different methods.

 I. By Secondary Generators or Transformers, with alternating current.

 II. The Edison or Parallel System, with continuous current.

 III. The Series or Bernstein System.

 IV. Multiple Series.

 V. Distribution with Secondary Batteries or Accumulators.