Patent GB-1059564-A (GB)
Title: Improvements in or relating to the synchronising of alternators
Inventor: GRIMSDALE RICHARD LAWRENCE
IPC: H02J3/42
Filed: 1962-11-23
Abstract: 1,059,564. Synchronizing. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. Nov. 15, 1963 [Nov. 23, 1962], No. 44453/62. Heading H2H. Automatic synchronizing means operating a circuit breaker to connect an alternator to an A.C. supply comprises speedmatching and voltagematching means, as well as phase-matching means adapted to operate the circuit breaker when the phase difference between the alternator and supply is such that, after making allowance for the inherent time lag in the operation of the circuit breaker, the initiation of closing of the breaker will result in closure at an instant when the phase difference falls within prescribed limits. A steam turbine which drives the alternator has a regulating valve actuated automatically by a centrifugal governor associated with a speeder motor 11 for adjusting the setting thereof. An exciter for the alternator is provided with an automatic voltage regulator 15, the alternator being connected to the threephase grid system when breaker 17 is closed by solenoid 19. After the alternator has been run up to full speed, the automatic synchronizing apparatus is switched on, the various components of the apparatus being fully energized after a delay caused by protective circuit XIII. The speed-matching unit IV acts through connection D, change-over unit VI, motor controller 33 and speeder motor 11 progressively to adjust the setting of the governor until the alternator is running about one per cent too fast. The voltage matching unit VII reduces the voltage difference across the circuit breaker to a low value, this unit operating through relays RL3, RL4, associated with setting unit 35 to adjust the setting of the automatic voltage regulator 15. When the voltage difference has been reduced to within the prescribed limits, the speed-matching unit IV applies pulses through connection E to pulse unit V to cause closing of the relay RL2 for a short period each time a beat occurs between the alternator voltage and the grid voltage, this effecting through the motor 11 a small reduction in turbine speed. When the alternator speed is within the permissible limits for synchronizing, speed-matching unit IV through connection C provides a signal to gate 39. When the phase difference between the alternator voltage and grid voltage is such that, allowing for the operating delay in the equipment, it is proper to initiate closing of the circuit breaker 17, then phase-matching unit VIII through connection K provides a further signal to gate 39. At this time the solenoid 19 is energized so long as protective relay RL5 has closed and as long as check units IX to XII are providing signals to the AND gate 39. The phase check unit IX and voltage check unit X respectively prevent closure of the circuit breaker unless the voltage and phase difference between the alternator and supply system are less than predetermined values. A speed-slip unit XI prevents closure of the circuit breaker unless the slip between the two frequencies is less than a predetermined value. A unit XII prevents closure unless the alternator speed exceeds the synchronous speed for the supply system. The various control units, which comprise transistors, are described in detail. In an alternative arrangement the voltage-matching unit adjusts the tap-setting of a transformer between the alternator and the supply system. The relative speed between the generator and supply system may remain at zero for an appreciable period but with an attendant phase angle error rendering the conditions unsuitable for synchronizing. Under these circumstances, the generator frequency is reduced below that of the system and the synchronizing cycle is repeated. In a modification, the gate 39 is replaced by two AND gates the output of each driving separate relays each having contacts in series with solenoid 19.