Patent GB-171795-A (GB)
Title: Improvements in electrical systems of automatic substations
IPC: F01B27/00
Filed: 1920-08-26
Abstract: 171,795. Metropolitan-Vickers Electrical Co., Ltd., (Westinghouse Electric & Manufacturing Co.). Aug. 26, 1920. Systems for conversion, employing rotary converters. - An automatic substation comprises a self-starting self-excited rotary converter, means for obtaining the correct polarity on the directcurrent side, means for raising certain of the commutator brushes until the correct polarity is established, means for connecting the converter to the direct-current side when its voltage reaches a predetermined value, and overload, low-voltage, and overspeed cut-out devices. When the voltage of the direct-current circuit 2 falls to a predetermined value, a relay 15 operates to complete the circuit of a relay 19, which in turn operates to close the circuit of the closing coil 27 of the main switch 5 coupled to a double-pole switch 12. A manually or clock-operated switch 30 is also provided to control the circuit of the relay 19. The switch 12 in its upper position closes the circuit of a brush-lifting winding 31 through the middle blade of the switch 14 in its lower position and through the switch 36 in the position shown, the winding 31 being energized by a transformer 23. The energization of the winding 31 operates a brush-lifting device 32 which lifts all except two of the brushes 33 from the commutator. A contact operated by the winding 31 is lowered to bridge the contacts 37 to complete the circuit of a relay 39, which operates to close the circuit of an electromagnet 42. The energization of the magnet 42 closes a switch 9 to connect the converter 3 to the low potential taps of a transformer 7, and a switch 13 is moved to its upper position. A polarized relay 44, which normally occupies a neutral position, closes the circuit of the electromagnet 48 of a field reversing switch 49 if the polarity of the converter 3 be reversed and when the voltage passes through zero the relay 44 reverses to de-energize the magnet 48. When the contact 47 of the relay 44 engages a contact 51 a relay 52 is energized to operate the trip coil 53 of the switch 9 and the switch 13 coupled therto is moved to the position shown to close the circuit of a relay 54. The operation of the relay 54 energizes the winding 57 of a switch 11 which operates to connect the full voltage taps of the transformer 7 to the converter 3. A switch 14 coupled to the switch 11 operates to close the circuit of a brush-lowering magnet 43 and to open the circuit of the operating-coil 27 of the switch 5. When a small difference of potential exists between the lower brush 33 of the converter 3 and the circuit 2, the contact 59 of a relay 58 drops to close the circuit of a relay 61, which operates to close the circuit of the operating-winding 62 of a cut-out 63, and a contact 64 engages contacts 66 to close the circuit of a magnet 68. The energization of the magnet 68 completes the circuit between the converter 3 and the circuit 2, and the circuit of the relay 61 is opened at the contacts 72, 73. The de-energization of the relay 61 opens the circuit of the operating-winding 62 of the cut-out 63. The switches 63, 5, 11 are provided with lowvoltage trip coils which operate to open these switches when the voltage of the supply circuit 1 falls below a predetermined value. A device 77 is adapted to open the switches 63, 5, 11 when the speed of the converter exceeds a predetermined value. A low-load relay 83 with a time-limit device 82 is adapted to de-energize the relay 19 and to energize a trip coil 85 of the switch 5; while an overload trip coil 88 is provided on the switch 5. A reverse-energy relay 78 is provided to discount the converter when it tends to operate as a motor.