Patent GB-313938-A (GB)
Title: Selective remote control of switchgear in electric substations
IPC: H02J13/00
Filed: 1928-03-17
Abstract: 313,938. Thomas, B., and Thomas, E. March 17, 1928. Selective distant control systems; tell-tale apparatus.-In a remote control system of the type described in Specification 227,478, [Class 38 (iii), Electric motor-control systems &c.], wherein indications of load in a circuit are obtained over a pair of pilot wires and the output of the circuit may be controlled over the pilot wires, the pilot wires are adapted to be selectively associated with any desired circuit by a step-bystep switch operated by a manually operated impulse sender. As shown, a step-by-step selector switch 12 is operated over line wire C by an impulse transmitter 11 to associate the lines A, B with any of the substation circuits, such as 63, 65 and thereby facilitate control or metering by the apparatus 14 through the intermediary of a manually-operated switch 13 or supervision by means of the indicator 38. Auxiliary selecting and indicating apparatus 18, 19 is adapted to provide detailed information regarding any one unit, e.g. a generator at the substation and a step-bystep indicator 17 provides a check on the synchronous operation of the switch 12. Alarm apparatus 15 is provided to signal the automatic operation of substation apparatus. Normal condition of system. In the normal position of the impulse transmitter, contact 44 may be operated to transmit a current determined by the resistance 47A over line C and send-contacts of hand switch 13 to energize the magnet 59 of the mechanism 54 which restores the selector 12 to normal. In the normal position of the selector and impulse sender, indicator 39 is operated over lines A, B and batteries 61, 45 in series. Selection of substation circuits. To effect a particular selection a manually operated catch 43 appropriate to the particular selection to be made is operated and the transmitter arm is moved until engaged and held by the catch. Meanwhile impulses the number of which correspond to the selection, are transmitted by the contact 37 over the line C to operate the stepping magnet 53 and thereby step the selector arms 52<A>, 52<B>, 52<C> on to the appropriate contacts. The impulse currents are weaker, as determined by the resistance 47<B> than the current which flows over the line C in the zero positions of the impulse sender and selector so as to prevent operation of the release magnet 59. Controlling selected apparatus or obtaining meter readings. When the pilot lines A, Bare associated with the appropriate substation circuit, the manual switch 13 is reset to connect the control and metering panel 14 to the line wires. The control and metering arrangements are similar to those described in Specification 227,478, [Class 38 (iii), Electric motor-control systems &c.]. Supervising position of apparatus, such as circuit breakers. The position of apparatus at the substation is supervised by two-position polarized indicators 38 operated over auxiliary contacts 11<1>, 11<2>, &c. of the impulse sender 11. A contact arm 33 operated together with the arm 31 connects the appropriate indicator to the selected circuit over the lines A, B. If the corresponding circuit breaker is in its " open " position the lines A, B are short-circuited at the substation and the indicator is operated by current of one polarity from the battery 45 at the control station, but if the circuit breaker is " closed " a battery such as 70 or 72 at the substation is switched into the line circuit in opposition to battery 45 to cause a reverse current to operate the indicator into its alternative position. Each indicator is arranged in a casing behind two windows. A manually operated indicator comprising a pivoted coloured screen is also provided for each pair of windows in order to provide a check on the position of the associated circuit breaker. Signalling automatic operation of a substation unit. If, for example, a circuit breaker is operated automatically a corresponding contact 85 energizes relay 80 which momentarily locks up over resistance 84. Battery 83 is then applied over switch 89 to line C to energize relay 86 of an alarm bell 15. Magnet 81 also is energized to restore relay 80 but the alarm continues to operate until stopped by the attendant. In the event that the switch 13 does not engage its upper contacts when the circuit breaker operates, the alarm is stored by the locked relay 20 until the switch is' reset. Indicating correct operation of selector. The stepping magnet 90 of a checking indicator 17 is operated over the line wires A, B in each selecting position of the selector 12 so as to obtain synchronous working between the selector and check indicator. The pointer of the indicator is frictionally coupled and is returned mechanically to zero when the impulse sender is restored. Signalling detailed information. Detailed information as to the operation of protective devices responsive to reverse current, overload, and overheating of the bearings, say,. of a substation generator may be ascertained by the selective apparatus 18, 19. When a protective device of a generator operates an alarm is given at the control station in the manner previously described and a corresponding contact such as 77<2>, 77<3>, &c. is operated. The impulse, sender 11 is then operated to ascertain the affected generator and operate the selector into the corresponding position. A circuit for a corresponding relay 76<A>, 76<B>, &c. is thereby operated td mark the appropriate contact of the switch 19. The switch 13 is then operated into its lowest position, and impulses are transmitted over the line B from the sender 18 to operate the stepping magnet 71 over the selected contacts of the switch 12 until the switch engages the marked contact when a circuit is closed from battery 72 over the line A to operate the appropriate indicator which is selected by a contact arm operable by the impulse transmitter. When the selector 12 restores to normal, switch 19 is reset by mechanical linkwork 75. Constructional details of selector switches. The selector 12 is provided with as many sets of contacts as there are individual circuits to be controlled and tested. Moreover, additional contacts may be provided to facilitate simultaneous switching of all the generators on to the bus-bars and ascertaining the total current of the substation. The selector is operated through pawl and ratchet mechanism by the stepping magnet 53 and the contact arms are adapted to remain in any set position until restored by the mechanism 54, which is operated when the impulse sender 11 is restored. Operation of magnet 59 closes the switch 60 in the parallel circuit of a motor and engages a worm-wheel 57 driven by the motor with a toothed wheel to restore the selector to normal. The stepping magnet 53 is short-circuited during the restoration. Impulse transmitters. The rotatable operating handle 31 is connected by a spring 34 to the contact arm 33 which is mounted on a make-andbreak disc 87 connected through ratchet mechanism 35 to a speed control gear 36. The gear 36 ensures uniform speed of the disc 37 and contact arm even although the handle 31 is operated quickly. The transmitter 18 is similarly constructed.