Patent GB-711485-A (GB)
Title: Improvements in load control systems for electrical generating units
IPC: H02J3/46
Filed: 1951-03-14
Abstract: 711,485. Automatic control systems. LEEDS & NORTHRUP CO. March 14, 1951 [March 14,1950; Feb. 19, 1951], No. 6185/51. Class 38(4) In an automatic control system for a plurality of electrical generating units supplying a distribution system, deviation of a system variable unbalances a selfbalancing controller re-balance of which unbalances networks to operate servomotors adjusting the inputs to the generating units and adjusting network impedances to rebalance the networks. In Fig. 1 alternators 15, 15A, 15B, driven by prime movers 16, 16A, 16B which may be Diesel engines or steam, gas, or hydraulic turbines, supply busbars 25 interconnected with another electricity supply system through a tie-line 28. Deviation of tieline load is detected by apparatus 24 to which signals variable in frequency with tie-line load may be transmitted over line 28. Apparatus 24 adjusts a potentiometer 11 in a circuit 10 to produce a D.C. input to an A.C. operated double-triode thermionic valve 36 the resulting A.C. output of which, through an amplifier 13, controls a reversible servomotor 14 adjusting the setting of a speed governor 19 of prime mover 16 in a sense tending to correct the load deviation. Follow-up is provided by motor 14 also adjusting a potentiometer 23 in a sense tending to rebalance circuit 10 and reduce the input of valve 36 to zero, Potentiometers 50A, 50B are also adjusted by motor 14 to unbalance A.C. circuits 10A, 10B and produce inputs to amplifiers 13A, 13B so that reversible servomotors 14A, 14B adjust speed governors 19A, 19B of prime movers 16A, 16B also in a sense tending to correct the load deviation. Follow-up potentiometers 23A, 23B are also provided in circuits 10A, 10B. The proportion of the. load deviation corrected by governor adjustment of any generating set is determined by the grading and setting of variable resistances on motor-balanced circuits 10A, 10B. The following modifications are referred to: (a) The input to amplifier 13 obtained from a motor-balanced A.C. circuit to which is transmitted the A.C. output of a potentiometer, in a remote control office, adjusted in accordance with tie-line load. With this arrangement several potentiometers controlling different power stations may be adjusted simultaneously in the remote control office. (b) Variable resistances in motor-balanced A.C. circuits for setting the datum load supplied by a generator or a station and for setting the percentage of any load deviation to be corrected by adjustment of a particular generator or station, (c) Automatic control of tie-line frequency or a function of tie-line load and frequency instead of load only. In the case of load and frequency the two components may differentially control a fluid valve in a pneumatic system balanced by a pneumatic servomotor which may control the generators directly or through a transmission system involving motorbalanced electrical circuits. (d) Addition of rate, inverse rate, and integral components of control into the motor-balanced systems by the addition of condensers, resistances, temperature-variable resistances or fluidpressure equivalents. The integral component may be automatically eliminated when balance is attained. (e) Contactmaking relays controlling reversible servomotors and a vibratory converter replacing valve 36. (f) A relay preventing servomotor operation if a remote signal disappears. (g) A plurality of motor-balanced circuits in which operation of each motor unbalances a circuit associated with another motor. (h) Load signals transmitted over power lines from a resistance-capacity valve oscillator the frequency of which is adjusted by resistances variable in accordance with load. Specifications 688,239, [Group XXXVIII], 710,348 and U.S.A. Specification 2,300,537 are referred to.