Patent GB-167049-A (GB)
Title: Improvements in and relating to electric generating systems
Filed: 1920-06-15
Abstract: 167,049. British Thomson-Houston Co., Ltd., (General Electric Co.). June 15, 1920. Equalizing load on generator; systems depending on the use of two or more machines.-A supply system is provided with a subsidiary power station adapted to be started and stopped in accordance with the head of water available iu a hydro-electric system, or in accordance with a variation of some constant of the system. When alternators are employed, means are provided for synchronizing automatically the subsidiary generator. The operation of the station may be controlled from a distant point independently of the automatic operation. The system is provided with thermal and overload safety devices. A two-phase system AC is normally supplied from a source S and a second generator 1 is started up and connected to the mains and disconnected and stopped in accordance with the head of water driving the waterwheel W in the following manner. When the switches 2, 9, 14, 18, 52, 53 and 65 are closed and the head of water is sufficient to close a switch 51 through a float 50 a relay 54 is energized over a switch 55 situated at a distant point and adapted when opened to prevent the starting up of the generator 1. A second switch 56 is also provided at the distant point by means of which the generator 1' may be started independently of the switch 51. The closing of the relay 54 energizes a relay 57 from a low-voltage phase A<1> A<11> over the contacts o, p of a controller C when in position k. The operation of the relay 57 closes the circuit of the controller motor M and of a friction brake B to move the controller C to position a. A relay 22 is then energized over o, aa and segments of controller C, contacts of de-energized relay 25, and the contacts of relays 59, 60, 61 and 62. The relay 59 is energized over a centrifugally operated switch 63 driven by an induction motor 64 and maintains the relay 59 energized unless the frequency of the system &c. exceeds a predetermined value. The relay 60 is an inverse time relay the winding of which is connected inseries with a current relay 69 to one phase of the generator 1, and the relay 61 is an inverse time relay connected to the other phase of the generator 1. The operation of the relay 22 consists of a relay 23 to phase A<1>, A<11> over the contacts dd, t and segments of the controller C and a switch 10 is energized to connect a motor 8 to the system &c. An exciter 7 for the generator 1 is quickly run up to speed by the motor 8 and energizes a relay 21 to close a locking circuit for relay 22 over the contacts v, o and segments of the controller C so that the relay 22 is maintained energized while the exciter voltage exceeds a pre-determined value and after the controller C leaves position b. In position b a point between the contacts of two relavs 70, 71 is connected to phase A<1> A<1> through the contact of relay 22 and contacts t, s, of the controller C, and as the generator 1 is not connected to the system &c. the movable contact of the relay 69 is in its upper position and the relay 71 is energized over a distant control switch 74. A circuit is thus completed from the mid point of contacts of relays 70, 71 over the contacts 45 of a limit switch 39 to the operating coil of a switch 38. The switch 38 operates to connect the motor 34. of the gate 33 of the water-wheel W to the phases A<1> A<11>; B<1>, B<11>. When the controller C moves from position C, at which its motion is arrested for a time, the circuit of the switch 38 is opened to stop the motor 34 until the generator 1 is connected to the system &c. at a later stage. When the speed of the motor 34 reaches a predetermined value a centrifugal switch 24 is closed to energize the relay 54, contacts o, z and segments of controller C, switch 24 and contacts y, q of controller C. When the controller C reaches position e the speed of the generator 1 will be approximately normal and the engagement of contact x of controller C with its segment places the coil of a switch 3 across phase A<1> A<11>. The switch 3 operates to place the unexcited generator 1 across the system &c., through the reactance 4. When the controller C reaches position f a relay 17 is energized to open the circuit of the resistance 20 and to connect the field of the generator 1 to the bus-bars 13 through the resistance 16. This small field is sufficient to pull the generator 1 into synchronism with the system AC and in the position g of the controller C the gate motor 34 is operated and a portion of the resistance 16 is short-circuited by the relay 19 to increase the field of the generator 1. In position h of controller C the reactance 4 is short-circuited and the circuit of the relay 37 is broken to stop the controller motor M. The generator 1 is now properly connected and when the current delivered to the system reaches a pre-determined value the current relay 69 breaks the circuit of the switch 38 and the gate motor 34 is stopped. If the current increases beyond this value the relay 69 operates to close the circuit of relay 70 which in turn closes the circuit of switch 37 and the motor 34 is energized to close the gate 33 When the water falls below a pre-determined level the switch 51 is opened and the relay 54 is de-energized to open the locking circuit of the relay 22. The de-energization of the relay 22 opens the circuit of the switch 3 to disconnect the generator 1 from the supply AC, opens the circuit of the relay 23 to de-energize the switch 10 which disconnects the motor 8 from the system AC, and opens the circuits of the relays 17 and 19 to de-energize the generator field. When additional generators are employed and these are excited by the dynamo additional relays 23<1> are employed which maintain the circuit of the switch 10 closed until all the relays 23, 23<1> are de-energized. The controller C is moved to its " off " position k by the deenergized relay 22 closing the circuit of the relay 57 to start the motor M. The de-energized relay 22 also closes the circuit of the switch 37 through the contacts 46 of the gate switch 39 and the motor 34 operates to close the gate 33 and the circuit of the switch 37 is broken at the contacts 46 by a member 40 engaging the tail-piece 43. The station may be shut down by opening the switch 55.