Patent GB-416609-A (GB)
Title: Improvements in and relating to protective electrical circuits for power lines and the like
IPC: H02H7/26
Filed: 1933-08-29
Abstract: 416,609. Protective cut-out arrangements. SIEMENS-SCHUCKERTWERKE AKT.-GES., Siemensstadt, Berlin. Aug. 29, 1933, No. 23955. Convention date, Sept. 24, 1932. Addition to 415,576. [Class 38 (v).] In the protective arrangements described in the parent Specification, on failure of the signal, means are provided for locking the switch release device against operation without delay when the direction relay indicates a fault in an adjacent section, and after a time interval when the direction relay indicates a fault in the section. In the arrangement shown in Fig. 1, a transmitter or modulator M at each station transmits the signalling currents to auxiliary lines 11. A receiving relay E at each station is tuned to the frequency of the transmitter at the next station, and while energized, maintains the circuit of the release coil 6 open at contact 7. On failure of the signal, relay E is de-energized and contact 7 closes, and the line switch 2 is opened if, at this time, the direction relay 5 closes contacts 10 and an exciting relay A closes contacts 8. If the direction relay does not point into the section, closure of contact 7 does not release the line switch, but a contact 14 is closed after a short time interval to energize the coil 15 of a tilting relay, which opens the circuit of the release coil 6 at contacts 9. If the direction relay points out of the section and closes contact 23, and if at the same time the exciting relay A has closed contact 24, the time delay switch 14 is short-circuited, and the coil 15 is immediately energized to open the contact 9. The tilting relay is reset after a time interval by energizing a coil 16 through a relay 21, the circuit of which has been prepared at contacts 13, 18. If oscillations are present in the line 1, the potential applied to the time relay 21 periodically varies, and the relay does not close its contact 22 until the oscillations have died down. In a modified arrangement, Fig. 2, the direction relay L has an armature 30 which can be brought into contact with a forward contact V or reverse contact R according to the position of a directionally responsive armature 32, which is provided at its tip with an insulated plate adapted to cover one or other of the contacts V, R. When energy flows into the section, connection is made with the contact V, and when it flows into the adjacent section, connection is made with the contact R. The circuit of the release coil 38 includes a normally open contact 39 and a normally closed contact 48. As long as the blocking signal is transmitted from the other station, a receiving relay 34 maintains open a contact 35 in the circuit of a relay 33, this circuit also including contacts 36 held closed by a relay 37 as long as the auxiliary lines connecting the two stations remain uninterrupted. On failure of the blocking signal, relay 33 closes contact 39 and prepares a circuit for the release coil 38, the completion of which circuit depends on the relay L. When relay 33 is energized to close contact 39, a contact 40 is reversed, and after a short time interval a relay 43 closes its contact 44 and establishes the circuit of a relay 45, which opens the contact 48 and locks the line switch against operation. If, at the time the failure of the signal energizes the relay 33, the direction relay L points out of the section, the relay 45 is energized over the rearward contact R, and the operating circuit of the release coil 38 is opened immediately at 48 without the intervention of timed relay 43. In either event, the operation of the relay 45 prepares a circuit for a relay 42 which, when the relay 33 is released on the recurrence of the blocking signal from the other station, operates a slow acting switch 47 and, after a time interval, opens the holding circuit of the relay 45, to restore the circuits to their normal working condition. In a further modification, Figs. 3<a> and 3b (not shown), the blocking signals are given over a pair of auxiliary wires to which the receivers are coupled by transformers, the primaries of which have centre tappings to which the transmitters are connected, so that the receivers at a station are rendered immune to the transmitters at the same station, and the number of frequencies necessary for the different blocking signals can be correspondingly reduced. In this arrangement additional relays are arranged to disconnect the receivers and render the protective circuit inoperative if the continuity of the auxiliary wires is interrupted. In all the arrangements, the direction relays may be arranged to be operated by the inverse output instead of the normal output.