GB438364A - Improvements relating to the regulation of supply frequency in electrical distribution systems - Google Patents

Abstract

438,364. Supply systems; frequency regulations speed governors. SOMERVILLE, T. B., 11, Entwisle Avenue, Davyhulme, Manchester, and ASSOCIATED ELECTRICAL INDUSTRIES, Ltd., Crown House, Aldwych, London. May 12, 1934, No. 14425. [Class 38 (iv)] [See also Group XXVI] In a supply system comprising generators in parallel there is provided means responsive to changes in frequency from a standard value tending to regulate power input to the generators but subject in the case of each generator or generator group to an over-riding control determined bv a loadsharing relay which prevents regulation when its effect would be such as to cause the load of that generator or group to diverge further from an amount determined by the sum of a programme value and the integrated frequency error. The frequency responsive means comprises a contact 7 moved at 10 second intervals by a master clock and a contact 10 moved by a cam 13 driven by a synchronous motor 14 and shaped so that the contact 10 makes its return movement in two steps with a 10 second interval between. The arrangement is such that impulses of a duration varying from zero to 5 seconds in dependence upon the integrated frequency error are applied through a " raise " or " lower" relay 19, 20 to the corresponding circuits of servo-motors 6 operating on either the governor settings of prime-movers or the field rheostats of motors 4 driving the generators 1, 2. The circuits of the servo-motors each include normally closed contacts 22, 23 to the opening coils of which the over-riding control is applied. The latter is determined in the case of each generator by a load-sharing relay comprising an induction disc 31 subject to three torques respectively proportional to (a) the power output of the generator represented by voltage and current coils 32, 33, (b) a programme value represented by a torsion spring 34, and (c) the integrated frequency error represented in sign and magnitude by the current in a coil 36. This current is derived from a time error rheostat 38 the moving contact 39 of which is displaced to one side or the other of a centre tap in accordance with the sign of the frequency error and by an amount proportional to the cycles gained or lost. This movement is produced by a reversible motor 41 controlled by the " raise " and " lower " relays 19, 20, this motor also serving to restore the contact 10 to synchronism with the contact 7 by superimposing corrective movement on the cam 13 either through a differential gear 18 or by operating on the stator of the synchronous motor 14. Adjustment of the network to compensate for clock errors may be effected on receipt of a standard time signal by decoupling the rheostat contact 39 from the motor 41 at a clutch 42 and resetting the contact in accordance with the observed clock error. The individual contributions of the several generators towards frequency regulation may be adjusted by varying resistances 45 in the circuits of the coils 36 of the load sharing relays. In a modification, Fig. 2, the servo-motors 6 operate on the governor settings 48 of primemovers to regulate input power and the two generators operate as a group having a common load-sharing relay 21 in which the torque proportional to output power is controlled by resistances 52 which are varied in accordance with the governor settings. A "weighted" or compensated average effect may be produced by making the resistances 52 different or causing their contacts to travel different amounts for a given load change.