Patent GB-227478-A (GB)
Title: Operation of semi-automatic electric substations
IPC: H02J13/00
Filed: 1923-07-17
Abstract: 227,478. Thomas, B., Thomas, E., and Shuttleworth, C. I. July 17, 1923. Selective distant control systems.-The starting and control of a substation machine from a central control station is effected by means of two pilot wires, which, after the machine has been started, are connected across an instrument shunt - or resistance in the direct-current circuit of the machine, whereby an indication of the load may be given by an ammeter at the control station. 'Operating means or relays are also provided in the pilot wires by means of which the field rheos- :tat can be operated in either direction to vary the output of the machine. The application of the invention to a Lacour motor-converter is shown in Fig. 1. In order to start the machine at the substation, the handle of a controller CO at the control station is moved to position 2, and current is supplied from the control station through the pilot wire B to an auxiliary motor M2 at the substation. The controller handle is retained in the depressed position as long as current continues to flow by a retaining coil 220. The motor M2 opens the slip-ring short-circuiting switch L, sets the field rheostat RS to the starting position, and finally closes the auxiliary switch L1, thereby opening its own circuit at the contacts 62, 63. and closing the circuit of another auxiliary motor M3 at the contacts 62, 64. The latter motor closes the high-tension switch H, and operates its auxiliary switches, one of which cuts off the current supply from the control station, whereupon the motor stops and the controller handle is released. In rising, the handle closes a switch 1345 and connects a voltmeter V2 across the pilot wires A, B, which are now connected to a tap 58 on the starting resistance of the converter, thereby enabling the progress of starting up and synchronizing the converter to be watched at the control station. A polarized relay R6 ensures correct polarity, and another relay R5 closes a contactor C1 and connects a choking coil across one phase of the converter to complete the synchronizing process. Finally a contactor C2 short-circuits the starting resistances, and, through an auxiliary switch 66, 67, energizes the auxiliary motor M2 from the direct current side of the converter, in order to close the switch L and open the switch L1. The pilot wires are now connected through relays R1 - - R4 to the terminals of a resistance 104 on the direct-current side of the converter. At the control station, the pilot wires are connected to the various contacts of the controller through resistances, so that different currents may be caused to pass along the pilot wires in different positions of the controller. In positions 6, 7 a current of 1.5 amperes passes through one or other of the wires and operates one of the relays R1, R3, to give a step-by-step move. ment to the field rheostat in one or the other direction for the purpose of varying the output of the converter. In position 3 a current of 3 amperes passes along pilot wire A through the relay R2, the operation of which opens the main switch H and shuts down the converter. The relay R2 may also be operated at any time during the starting process by sending a current from the control station, the controller handle being moved into the position (1) for this purpose. In position 4 a current of 3 amperes passes along the wire B and operates the relay R4 to open the direct-current circuit-breaker C3, the latter being closed bv moving the controller handle into position 5. In position 8 the pilot wires are connected to the ammeter AM. A voltmeter VI is connected through resistances to both pilot wires, so that it does not disturb the readings of the ammeter. The construction of the controller is shown in Figs. 3 and 4. The contact member is pivoted at 309 and swings about a central pillar 303 mounted on the base plate 301, and can only be depressed, to operate one of the control circuits, in one of the, eight control positions determined by notches in a fixed dial plate 302. An indicator disc 317 mounted on the dial plate is moved step-by-step through pawls 321. 322 to indicate the position of the rheostat RS whenever the controller handle is depressed in positions 6 or 7. An interlock 323 preventthe depression of the handle in the starting, position 2 unless theindicator disc has been first moved by hand to the starting position, indicated by pointers 325, 326. An auxiliary switch 335 opposite position 3 may cause the lighting of an indicator lamp at the control station every time the controller handle, passes position 3 in the clockwise direction, the lamp being extinguished on the reverse. movement of the handle. An auxiliary switch 329 may be operated in position 5 for simultaneously connecting a number of machines in parallel. A modified arrangement for use with a rotary converter having a sepatate starting motor is also described. In this arrangement, the polarized relay is associated with a reversing contactor, for correcting the polarity of the converter when necessary.