Patent GB-229388-A (GB)
Title: Improvements in or relating to the control of electric substations
IPC: H04Q9/04
Filed: 1923-11-21
Abstract: 229,388. Reyrolle & Co., Ltd., A., Leeson, B. H., and Minton, R. C. Nov. 21,1923. Selective distant control systems; tell-tale apparatus.-Electric power substation apparatus is controlled selectively according to the frequency of currents sent from a. control station over a pair of pilot wires, the selection effecting the closure of different local circuits, each of which is dependent on a relay device sensitive to a particular frequency, the various devices being grouped into an instrument termed a " frequency selector." Supervision is provided for by causing the action of a relay device to alter the current in the pilot wire circuit and thus give indications at the control station. In the " frequency selector each unit consists of three vibratory contact-makers mounted on tuned reeds D, Figs. 2 and 3, which vibrate under the action of a permanent magnet D<3> and windings D<6> carrying the alternating current of the pilot wires. The periods of the three reeds differ slightly among themselves in order to allow a little latitude in the frequency determining vibration, and differ considerably from the periods of the other similar units in order that only one element shall respond at a time. Instead of the permanent magnet, a direct current coil on a soft iron core may be used. An instrument in which twelve units, each comprising three tuned contact-makers, are combined with a common polarizing and controlling magnet is described. A selective contact-maker for the closure of any one of a large number of local circuits is operated successively along two co-ordinates by two successive actions of the frequency selector. A third co-ordinate may be added, allowing 1728 local circuits to be controlled with a frequency selector of twelve units. The control station includes an alternator coupled to a motor the speed of which is variable by shunt field regulation. A master controlling handle allows first the desired speed to be obtained by reference to a frequency meter, and secondly the alternator to be switched on to the pilot wires. Figs. 13 and 14 show diagrammatically the arrangements of the master handle M and the principal circuits required for transmission and supervision. Movement of the handle parallel to the panel N traverses a contact M<5> over a row of studs N <2> connected to tappings of a shunt field resistance <p2> belonging to a motor P which drives the alternator P<1>. A limited movement of the handle in a direction at right angles to the first, without affecting the contact M<5>, switches in at will either preliminary contacts to a frequency meter <p3> and a voltmeter R<5> or transmission contacts to the pilot wires P<4>, P<5> through a visual indicator Q and a hold-on magnet R. When the transmission contacts have been made, the indicator exposes a green disc showing the due completion of the pilot wire circuit, and when the selected circuit has been closed at the substation the fact is announced by the indicator changing to a red disc due to the insertion of a resistance across the pilot wires. The closing of a selected circuit at the sub-station may be used to start up a motor-converter set by means of a group of timed relays in the manner described in Specification 228,275, [Class 38 (v), Electric switches &c.]. Specification 227,523, [Class 38 (v), Electric switches &c.], also is referred to.