Patent GB-786082-A (GB)
Title: Improvements in or relating to electric power supply networks
Inventor: FRIEDLANDER ERICH SIEGFRIED
IPC: H02J3/48
Filed: 1955-02-14
Abstract: 786,082. Control of several motors; controllers. GENERAL ELECTRIC CO., Ltd. Jan. 12, 1956 [Feb. 14, 1955], No. 4314/55. Class 38 (3). [Also in Group XXXV] Relates to networks each comprising a large number of alternators supplying common load circuits, the networks being interconnected through a link of limited current-carrying capacity, wherein it is necessary to control the power input to a network relatively quickly in response to a power demand. The power input is controlled by regulating the least efficient alternators so that the machines with high efficiency may operate permanently at maximum output. Apparatus for regulating these less-economical machines comprises a face plate controller having a rotary contact 7 driven by a motor 8. Fixed contacts 10 of the controller are each associated with one machine, and the engagement between the rotary arm and each contact causes a control signal to be sent to the loadsetting motor of the particular machine associated with that contact. Upon the total power output of a network departing from the required power by a certain amount, the motor 8 is energized from an error amplifier 9 and runs at a speed dependent upon the magnitude of the error, and in a direction dependent upon the sense of the error. A polarized relay 22 having a change-over contact 23 ensures that the control impulse applied to any one machine is positive for increasing load and negative for decreasing load. The duration of the control signal is adjustable for each machine to take account of the different control characteristics of the separate machines, a timer 11 being associated with each alternator and receiving a control impulse from the controller, the sense of this control impulse deciding whether the governor motor 12 operates in a positive or negative direction. When there is a large error, the rotary arm may move so quickly that the control operation of a machine has not been completed before the arm again engages the associated contact in the course of the next revolution. The control impulse will then be repeated and the duration of the signal is measured from the second repeated impulse. The machines which are to contribute to the power control of the network are selected in a control room 13 as well as in the local position 14. A timer arrangement for each machine comprises a relay 15 which is energized on receiving an impulse to close contact 15a and energize relay 16 which has a self-holding contact 16b. If the impulse is of short duration so that relay 15 drops out, contact 15b closes to energize relay 18 which opens contact 18a to interrupt the holding circuit of the relay 16, this taking place at a predetermined interval after the end of the impulse. During this period, a control circuit 20 or 21, depending upon the sense of the impulse which is detected by a polarized relay 19, receives a signal through contact 16c. If a long impulse is applied to the relay 15, the holding circuit of the relay 16 is interrupted by the opening of contact 17a at a predetermined period after the energization of the relay 17. The means for sequentially supplying control impulses to each alternator may be used to control its frequency. The control impulses may be of different frequencies depending upon whether the output of the machine is to be raised or lowered.