Patent GB-342903-A (GB)
Title: Improvements in or relating to systems for the automatic control of electric generating plant
Filed: 1930-02-07
Abstract: 342,903. Running generators in parallel. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London.-(Assignees of Meador, B. F. ; 5029, Wyandotte Street, Kansas City, Missouri, U.S.A.). Feb. 7, 1930, No. 4203. Convention date, Feb. 7, 1929. [Class 38 (iv).] In an automatic generating station comprising a generator and an automatic voltage regulator wherefor one station is automatically shut down and placed in condition for restarting when an abnormally high station voltage occurs due to a sudden decrease in the load, but if the high voltage is due to a failure of the regulator or of the generator excitation one station is locked out. The Figure shows a water wheel 2 driving a generator 3 and coupled exciter 4 with an automatic field regulator 27. The generator is adapted to run in parallel with a system 22. The station is started by closing a master switch 20 if the line 13 is alive but it may be started from a distant station, if switch 20 is normally closed, by means of a switch 23. The transformer 40 then energizes a master relay 19 by way of interlocks on an overvoltage relay 38, a lock-out relay 37, a stopping relay 32 and a speedresponsive relay 25. The master relay 19 opens the water valve 5 by coil 10, closes the circuit of trip coil 17 and prepares the circuit of closing coil 16 of circuit-breaker 14 and makes a retaining circuit for itself independent of the interlock on the speed responsive relay 25. At synchronizing speed, the switch 24 closes and with adequate exciter volts the speed responsive relay 25 energizes time-relay 26 to complete the circuit of closing coil 16 across the exciter. The generator armature 3 is thus connected to the circuit 13 and simultaneously the field switch 15 is energized by an auxiliary switch on the circuit breaker 14, the generator pulls into synchronism and its voltage is automatically controlled by the Tirrill regulator 27. The speed of the turbine 2 is maintained constant by a governor 11 driven by a synchronous motor 12. The circuit of the stopping relay 32 is prepared at auxiliary contacts on the field switch 15. The speed responsive relay in closing connects the over-voltage relay 38 across the transformer 40 in series with a resistance 39. Current responsive relays 35, 36 energize the lock-out relay 37 on excessive load. Operation of either relay 37 or 38 de-energizes the master relay 19 and trip coil 17 and shuts down the station, but the contacts 41 of the latter reclose and automatic starting takes place when this relay alone operates. Failure of the regulator 27 or the excitation causes a relay 40 to short-circuit resistance 39 so that normal voltage operates the over-voltage relay 38. A current responsive relay 29 ensures that should the overvoltage regulator operate when a predetermined load is being carried the lock-out relay shall operate and prevent automatic restarting, but in order to enable the station to be shut down by disconnecting the circuit 13 at the switch 23 the circuit of the over-voltage relay is interrupted by the fall of the relay 29, when one load current ceases and this movement energizes a stopping relay 32 which interrupts the master relay circuit.