Patent GB-552092-A (GB)
Title: Improvements in or relating to the control of the load distribution of a plurality of unequal power generator units or other energy transforming units supplying a common system
IPC: H02J3/46
Filed: 1941-09-03
Abstract: 552,092. Control of power generating and supply systems ; calculating apparatus. KAUFMANN, P. G. Sept. 3, 1941, Nos: 11265, 12895 and 16246. Class 38 (iv)] [Also in Groups XIX and XXVI]  Load distribution ; frequency ; fluid pressure; selecting sources in service.-The load distribution amongst a number of energy transforming units of any kind is regulated so that maximum efficiency of the whole is obtained, e.g. minimum input for every output; efficiency may, however, be expressed as a rate of B.T.U. insteam generators or even as financial efficiency where different kinds of fuel are employed. Means responsive to the frequency of the output of an A.C. generating system or to the steam pressure of a common steam main may control the distribution of load amongst the individual units or provide an indication by which they may be manually adjusted so that whatever the total load all units shall work on points in their input-output characteristic curves that have the same slope. This relationship may, however, be modified in respect of another variable such as power loss in a tie line of a distribution system. Fixed plates 4 having slots 5 each shaped to the aforesaid characteristic of a unit may co-operate with plates 6 having straight slots 7 and linked at their ends to members 11 rocked simultaneously by a lever 20, e.g. in accordance with steam pressure variations; rollers 8 engaging co-operating slots 5, 7 are each positioned at points in the slots 5 which have the same curvature whenever moved by a change in steam pressure. The rollers are coupled to rods 3 so that each adjusts, e.g. a contact on a resistance 27 in accordance with the ordinate of the characteristic curve defined by the position of the roller. This may be the input or output co-ordinate according to the mode of regulation. Alternatively cams 42 each constructed so that radial dimensions correspond to output ordinates and angular displacement to the slope of the characteristic may operate upon the resistances 27 as indicated in Fig. 3. In all cases the scale used to represent the slope of the characteristic may be logarithmic. The rods 3, 3a may serve as indicators of control adjustments required. The resistances may each comprise an element in a Wheatstone bridge causing when unbalanced operation of a reversible electric motor to adjust the air supply to the steam generator it controls. In a load distribution control for AC. generators in parallel the resistances may be calibrated so that the positions of rotary contact arms correspond to slopes of the characteristics, e.g. to a logarithmic scale, and the value of the resistance at each position to the appropriate output ordinate ; all the arms would be fixed on common shaft so that all controls would operate on the same slope at any time. This shaft would be operated by a reversible motor by any deviation of frequency, or other condition of the load circuit from normal and the Wheatstone bridges would operate each through a reversible motor on, e.g. the governor adjustment of the appropriate prime mover. Bodily movement of a logarithmic cam or rheostat may be used to introduce a compensation factor to a logarithmic scale. Similar arrangements would be applied to station groups operating on a common system so that the total load would be shared between stations and each station maintained at maximum efficiency. Where stations are not connected by tie lines wattmeters compare the incoming tie line load at each station with the outgoing load on another tie line and transmit control to a regional control centre whereby bodily adjustment is effected and all the logarithmic control resistances in proportion to the tie line losses at the respective stations, thereby modifying the action of the frequency controller upon the controls in individual stations. Voltmeters across each control resistance indicate load values. Means are provided to prevent overload on a tie line by automatic means changing the calibration of the wattmeter or the control they transmit, in response to overload conditions. To control automatically the number and selection of units which will give the best efficiency at any load cams constituting together an envelope of the input-output curves of all units is adjusted in accordance with total load to cause a bar carrying rollers riding over the cams to indicate the units for service or-to effect electrical connections through the cams whereby they are automatically brought into or taken out of service.