Patent GB-420405-A (GB)
Title: Improvements in or relating to remote control systems for electric supply networks
IPC: H02J3/14
Filed: 1933-10-30
Abstract: 420,405. Switching systems for consuming devices. HALLOWELL, E., 10, Moor Grange Rise, West Park, and NORTHERN UTILITIES TRUST, Ltd., Permanent House, The Headrow, both in Leeds. Oct. 30, 1933, No. 30075. [Class 38 (iv)] Energy consuming devices are automatically removed from an electric circuit as the total load reaches a peak value by A.C. or D.C. impulses of selected frequency (or frequencies), duration, or intensity transmitted over the circuit, or over auxiliary conductors such as a telephone circuit, by a device responsive to the load. Such consuming devices may be removed in sequence as the unrestricted load continues to rise, and the sequence and duration of disconnection may be determined according to the proportion of energy stored in such devices as have energy storing means. The setting of the load responsive device may be automatically increased with increase of the unrestricted load. As shown in Fig. 1 a restricted load C on a substation B is adapted to be disconnected by a relay 24 in a circuit tuned to the frequency of sources 15, one or other of which is rendered effective for this purpose, either by excess of load in the circuit 13 or by excess of the total load on the main supply station A, according to the particular excess current relay 20 operated. In the latter case a relay 22 first responds to the impulses transmitted over the main conductors 11, 12 ; thus the maximum load on substation such as B is controlled by their respective control devices and a master control is effected by the control device at the main station A. Each of the consumers of restricted load may be provided with one of the arrangements now to be described. The armature of the remote controlled switch, Fig. 2, which permits the load switch 28 to open may be controlled by a dashpot having valves controlled by a plunger 37, operated, for example, by a bimetallic strip 39, so that a high temperature of storage medium associated with the consumer increases the time delay on an opening movement of the switch and increases it on closing. Further the armature is arranged to be actuated by the strip 39 to cause the switch 28 to open irrespective of load conditions when the storage medium reaches a maximum temperature. In a modification the dashpot contains a liquid the viscosity of which varies with the temperature of the aforesaid storage medium. In these arrangements the armature continues its movement after actuating the switch and its return movement, which occurs when the control impulse ceases, is due to gravity or spring control against the action of the dashpot; thus the last switch to open is the first to close. Fig. 4 shows a switch operated by a bimetallic element 43 heated by the current in the tuned circuit and subject also to the heat of the storage medium. The heating coil is lagged to introduce a time delay in the reclosing of the switch. The heat due to the control current and that due to .the storage medium co-operate in the control of the load. Preferably the inductance of the heating coil is increased by using iron in the bimetallic element 43 and for a connecting element 47. A variable setting for the thermostatic control may be obtained by mounting the end of the strip on a pivot 48. The heating element need not surround the strip. The switches described may be operated through ratchet mechanism, the control current may be amplified by a relay circuit, and other delay devices than dash-pots may be used. Where a pumping load is controlled a float may operate upon the plunger 37, Fig. 2. Where the time lag depends on temperature this may be varied by a rheostat, controlling a heating element in contact with the control switch, actuated for example by a float. The succession need not be determined by current requirements but may be preselected, by adjustment of time lag devices for example. To prevent consumers of restricted load from being disconnected when there is an increase in the unrestricted load the operating current of the relays 20 may be automatically increased if the removal of all restricted load does not remove the overload. As shown in Fig. 5 the operation of the relay 20 compresses a spring 54 which slowly forces a valve 55 inwards until eventually liquid from a reservoir 59 flows out to increase the loading on the relay armature. A preferred form is shown in Fig. 6, wherein the action of the coil 20 on a switch 60, controlling the superposition of selected frequency on the mains, is resisted by a spring 66 restrained by a weighted ratchet 69. The switch 60 also energizes a coil 73 which after a time delay causes an abutment 71 to open the switch 60 and increase the normal tension of the spring 66. In place of the coil 20, a current-carrying bimetallic strip may be used. The time lag at substations will be less than that at the main station. Time lag devices may be connected to the armatures 50, 64 to prevent operation on transient overload.