Patent GB-177141-A (GB)
Title: Improvements in automatic electrical substations
Filed: 1922-01-06
Abstract: 177,141. Metropolitan - - Vickers Electrical Co., Ltd, (Assignees of Moss, C. M.). March 14, 1921, [Convention date]. Systems for conversion employing rotary converters or rotary transformers.-An automatic substation, comprising rotary converters or motorgenerators adapted to be started and stopped in accordance with the load on the direct current mains, is provided with devices adapted automatically to start a second or a third converter when the load on these mains reaches a predetermined value. When a converter fails to start, means are provided to render its control circuits inoperative, and the succeeding converter is started up. When a load is placed on the direct current circuit 4, a voltage relay 24 operates to close a switch 25, thereby placing the winding 26 of a switch 28 across the leads 100, 101 when a selector switch 21 is closed. The closure of the switch 28 energizes the winding 30 of switches 32, 33 and 34. Closure of the switch 32 maintains the energization of the winding 30 and. closure of the switch 33 connects the conductor 200 to the lead 101 and causes a switch 19 to close and place the shunt field winding 18 of a converter 5 across its armature. The winding 38 of a starting switch 10 is also energized over a switch 36 and an interlock switch 39 associated with a running switch 11. The operation of the switch 10 connects the alternating-current side of the converter 5 to low-potential taps on the transformer 7, 8. Simultaneously with the energization of the windings 35 and 38 the winding 41 of a switch 6 is energized to connect the transformer 7, 8 to the alternating-current mains 3. A polarized relay 42 operates to ensure correct polarity of the converter, and when this is obtained its contacts 44 and 46 engage to energize a winding 47 which opens the switch 36 and closes the switches 48 and 49. The opening of the switch 36 de-energizes the winding 38 to open the switch 10 and to close switch 50, thereby energizing the winding 51 of the running switch 11 which is closed to impress the normal line voltage upon the converter 5. The energization of the winding 51 also opens the switches 39 and 52 and closes the switches 53 and 54. When the voltage on the direct-current side of the converter reaches a predetermined value a switch 56 is closed by a winding 55 to energize the operating coil of a switch 16 to connect the converter 5 to the direct current circuit 4 through resistances 12 and 13 and series relays 14 and 15. A switch 59 is also closed to complete the circuit of the coil of switch 62, provided that the switch 58 is not open, and the switch 62 is closed to short-circuit the resistance 12. If the current conditions are still normal, a switch 64 associated with the switch 62 completes the circuit of the operating coil of a switch 66 which operates to short-circuit the resistance 13 and the series relay 14. A switch 67 associated with the switch 66 completes a circuit containing the re-setting coil 68 of a lock-out relay 69. The relay 69 is also provided with an operating coil 73 adapted to raise the member 71 one notch for each energization, the coil 73 being controlled by a switch 76 associated with the switch 6. The relay 69 is provided with two switch contacts 74 and 75, the former of which operates to shortcircuit the winding 30 to de-energize the conductor 200 if the converter fails to start, and the switch 75 completes a circuit to initiate the control of the next converter. Overload relays 77 are also adapted to short-circuit the winding 30. When the load on the circuit 4 reaches a predetermined value a thermal relay 81 operates to energize the relay 27<a> of a second unit. The second unit may be switched in if the first unit is not connected within a definite interval of time and if the fault is such that the relay 69 is not operated. Under these conditions a time-element motor relay 84 comprising a motor 85, two magnetic clutches and two switches 88 and 89 are provided. When the control relay 24 operates to close the switch 25 a circuit is completed through the switch 60, operating coil of relay 90 and a switch 34<a> of the second unit. The relay 90 operates to energize the clutch coil 86 and motor 85, the circuit being completed through a switch 92 on the overload relay 93, and a switch 53 associated with the running switch 11. If the converter is connected up the circuit of the motor is broken at the switch 60, but if it is not connected up in the predetermined time the switch 88 is closed to energize the relay 37a to connect up the second unit. To disconnect the unit when the load on the circuit 4 decreases to a pre-determined value a winding 93, shunting a resistance 94, allows the switches 92 and 95 to close, and the motor 85 and clutch winding 87 are energized to close the switch 89 after a predetermined interval of time, thereby shunting the relay winding 30 to de-energize the conductor 200. If after the motor 85 has begun to operate the load on the circuit 4 increases the switches 92 and 95 are opened, and the movable element of the switch 89 is returned to its initial position. A complete description of the motor relay 84 is given in Specification 150,730, [Class 38 (v), Electric switches &c.]. Specification 171,795, which describes an automatic converter substation, is referred to.