Patent GB-675835-A (GB)
Title: Improvements in means for governing power stations
Inventor: BRODERSEN EINAR
IPC: H02P9/42
Filed: 1951-01-05
Abstract: 675,835. Automatic speed control systems; running generators in parallel. ALLMANNA SVENSKA ELEKTRISKA AKTIEBOLAGET. Jan. 5, 1951, No. 397/51. Class 38 (iv). The speeds of two or more alternators driven by water turbines are controlled by comparing the frequencies of tachometer alternators with the resonant frequency of tuned circuits, additional components being added to prevent hunting, to limit the total power input to the turbines, and to effect load sharing. The turbines 7, 8 drive alternators 9, 10 and A.C. tachometer generators 11, 12, either one of which may be selected as the reference standard and connected to bus-bars 20, 21 by a switch 22. The selected output is connected by transformers 27, 28 to the anodes of a balanced pair of valves 25, 26, and connected to the grids of these valves via a tuned circuit 41. A deviation from the resonant frequency of circuit 41 changes the phase of the grid voltage with respect to the anode voltage, unbalances the output and actuates a hydraulic servo-motor 3 by differential energization of coils 29, 30. A shaft 5 corrects the setting of the turbine guide vane apparatus. A control circuit 2, servo-motor 4, and shaft 6 similarly control the turbine 8. The shaft 5 actuates the sliders of potentiometers 13, 15, 17, and shaft 6 actuates corresponding potentiometers 14, 16, 18. A voltage from bus-bars 20, 21, rectified at 49 is applied to potentiometer 13. A change in voltage proportional to the change in movement of shaft 5 is obtained from the slides and is applied to differentiating networks 31, 34, 32, 35, or the grid circuits of valves 25, 26, to reduce hunting. The potentiometer 14 is similarly connected. Voltages tapped off potentiometers 15, 16 are proportional to the setting of the turbine guide vane apparatus and therefore proportional to the power input to the turbines. These voltages are added by transformers 52, 53 to provide a voltage corresponding to the total power input. Further generating units can be added at terminals 62, 63. The total voltage is compared with a reference voltage set on potentiometer 57 and a portion of the resultant is tapped off a further potentiometer 55 and applied by a transformer 59 to the inputs A, A, of the regulating circuits. This produces a speed drop when the total power exceeds that for which the potentiometer 57 has been set, the percentage regulation being determined by the setting of potentiometer 55. A potentiometer 60 allows a further voltage to be injected into the primary circuit of transformer 59 by which the basic speed of the generator sets may be varied. Voltages appearing between the slides of potentiometers 17, 18, and a conductor 19 common to all generating units are proportional to the difference between the mean power input and the individual power inputs and these voltages are applied to the regulating circuits at points B, B, to regulate the mutual load diversion. The potentiometers 17, 18 may be graded in order to obtain the most economic division of load. It is stated that transductor regulators controlled by a number of exciting windings may replace the valve circuits. Specification 568,108, [Group XXIX], is referred to.