Patent GB-329400-A (GB)
Title: Improvements in or relating to the automatic control of electrical power supply units
IPC: H02P5/68
Filed: 1929-02-22
Abstract: 329,400. General Electric Co., Ltd., and Angold, A. E. Feb, 22, 1929. Running generators in parallel.-A number of supply units are automatically withdrawn from operation in circular sequence under the control of load responsive means so that when a unit is withdrawn the remaining units operate at or over their full or most efficient loading. The last machine may be withdrawn only when the load has fallen to a small fraction of its full-load rating. If there are n-1 units in operation a unit is withdrawn when the power supplied by that unit is less than that at which it is withdrawn when n units are in operation. Two multiplecontact relays 6, 7 effect the initiation in circular sequence of known means for starting up and shutting down the units respectively and a selective device 17 of the kind described in Specification 329,678, [Class 38 (v), Electric switches &c.], renders the contacts of these relays effective in accordance with the number of units in operation. The load responsive means comprises an underload relay 8 and an overload relay 9 co-operating respectively with the relays 7, 6 and appropriate contacts shown on the right and left respectively of the moving contact 82 of the selective device 17. The setting of the underload relay 8 determines the load conditions under which the next machine in the sequence is withdrawn from operation. Each of the circuit-breakers 31 - - 34 of the units 1 - - 4 has an auxiliary contact 35 which, when the unit is paralleled, energizes a solenoid 36 - - 39 of the selective device. All the solenoid cores are interconnected by links 101 - - 103 which support the contact 82 so that its position depends only upon the number of solenoids energized, i.e. the number of units in service. With all units idle as shown a voltage relay 52, on low volts of the system 5, energizes the relay 6 from bus-bars 54, 55 by way of contacts 82, 61, 58 and the first unit in sequence is started and paralleled. Rising output from this unit lifts the cores of overload and underload relays 9, 8, opening contact 21 and closing contacts 13, 16. The contact 82 having been raised into engagement with contact 63 the connection 13, 16 energizes once more the relay 6, contact 58 being now open, and a second unit is paralleled. The contact 82 is raised a further step and the process continues as load rises until all units may be in operation and contact 82 in engagement with contact 76, contacts 21 - - 24 being open and contacts 13 - - 15 closed. As the load falls the contacts 24 - - 21 close in succession at load values depending upon the adjustment of the relay 8 and, in the system described, these closures occur at 2.8, 1.8, 0.8 and 0.05 times the full load output of a single generator. The contact 82 is in engagement with the appropriate right hand fixed contact of the relay 17, according to the number of machines in service, each time a contact 24 - - 21 closes, and the closing- down relay 7 is accordingly energized to shut down units in sequence. Specification 261,844 also is referred to.