Central-Station Electric Lighting / With Notes on the Methods Used for the Distribution of Electricity

by Killingworth Hedges

The Vienna Central-station.

The practical success of the Battery Transformer system has been demonstrated at Vienna, where an installation of five thousand lamps in the Opera House and Burg Theatre was maintained for the past year from a distributing station 1,400 yards away. The boilers are fixed in a basement formed by excavating the court-yard of a private house to a depth of 15 feet 6 in. below the street level; the building itself is utilised partly for offices and partly as a large dynamo and engine-room. Each dynamo is designed to give an output of 72 kilowatts or 120 ampères, at 600 volts pressure. The current is led by means of a lead-covered cable underground to the accumulators, which are erected in groups of 52 cells each, so as to give 100 volts to the lamps, with a comfortable margin. The total pressure required to charge the four groups of batteries in series varies from 430 volts at the time the batteries are giving off work, to 480 volts for the short time during which the charge is being completed. During five hours of lighting about two-thirds of the current comes direct from the dynamos; but during this time, for short periods, the demand for current often increases to such an extent that these proportions may be reversed, and the batteries supply two-thirds of the total.

The regulation of groups of batteries placed in series is not a difficult matter, and will be understood by referring to the following diagram, [Fig. 27]:—

Fig. 27.

The four battery stations mentioned as arranged in series are represented. The current may be supposed to enter at the right hand corner, passing through the first battery with the lamps parallel to it, and from that battery to the commencement of the next, and so on through the third and fourth, the current being varied at will at the central-station, or kept constant by means of an electrical governor. The potential for each of the four groups of lamps is maintained in the following manner:—In each group one terminal is kept permanently connected to one of the discharge mains and to one of the charging mains; the other terminal can be shifted from cell to cell according to the E. M. F. required in the corresponding lamp circuit by means of a contact regulator. This movable terminal is shown by the bunch of lines at one extremity of each battery group. The rule for charge and discharge is, that the terminal cell at the regulating end of the battery is so arranged that it neither receives nor gives off current, so that there is no loss of energy in the shape of E. M. F. The contact regulator, which was designed by Mr. Crompton for use at Kensington Court, is shown by [Fig. 28]:—

Fig. 28.

Central-Station.

The ring contacts are arranged in a line in such a manner that a circular contact-piece, made of thin sheets of copper, can be forced through them in turn by means of a central screw spindle. The mains for charge and discharge are attached to the fixed disc contacts on the central screws, and the regulating cells of the battery are coupled to their respective contact rings by sockets at the back of the board.

The difficulty with the battery transformer system is the introduction of 400 to 500 volts into the houses, which would be necessary without the batteries are always fixed in sub-stations from which a low-pressure current, say of 100 volts E. M. F., could only be distributed.

A method has been devised by Mr. Henry Edmunds to obviate this disadvantage. He also uses the high-tension current to charge the batteries, but by means of a distributor, which is automatically worked by the current, each group of cells is charged in turn, when it is entirely cut off from the supply main to the house, through which current is perhaps being taken for lighting purposes. The system is now being adopted by the Cadogan Electricity Supply Company, Chelsea.