Patent GB-415576-A (GB)
Title: Improvements in and relating to protective electrical circuits for power lines and the like
IPC: H02H7/26
Filed: 1933-08-08
Abstract: 415,576. Protective cut-out systems. SIEMENS-SCHUCKERTWERKE AKT.- GES., Siemensstadt, Berlin. Aug. 8, 1933, No. 22204. Convention date, Aug. 8, 1932. [Class 38 (v).] In a protective arrangement for power lines in which switching stations at each end of a section of the line are operatively connected together through an auxiliary channel over which signals are arranged to be sent in such a manner that the release of the line switch is dependent on the operation or condition of relay devices at the two ends of the section, a supervising relay device is provided which, upon an interruption in the working of the signal transmitter at the same end of the section or an interruption in the reception of the signal from the other end of the section, renders the protective circuit inoperative, unless such interruption coincides in point of time with a fault arising in the section to be protected. In the arrangement shown in Fig. 1, each end of a section 4 is provided with a line switch 1 which is opened on energization of a release coil 2. At each end of the section, a transmitter S transmits high-frequency oscillations to the line through a normally-closed relay 5 and a transformer 6. A receiving relay E is connected through a band filter F to a coil .8 which receives the beat frequency of the transmitters through windings 7, 9. As long as the beat frequency is received, the relay E is energized and maintains its contacts open. The circuit of the release coil 2 is completed through contacts on a direction relay R, the relay E, and a normally-closed relay Z. When a fault occurs in the section 4, both direction relays R point inwards and disconnect the transmitters S from the line by energizing the relays 5 ; the beat frequency is no longer received, and the relays E close to energize the release coils 2. If the fault is in an adjacent section, the direction relay at one station closes, so that the transmitter of that station no longer transmits to the other station, but the direction relay at the latter station remains open, so that although the relay E closes, due to failure of the beat frequency, the release coil 2 is not energized. Closure of the relay E, however, energizes relay Z, which opens after a time interval and renders the protective circuit inoperative. In the same manner if the beat frequency ceases, due to a failure in the transmitters or signalling arrangements, the protective circuit is rendered inoperative by the action of the relay Z, unless the relays R indicate at the same time a fault in the section. Instead of using the power lines for the transmission of the signals, auxiliary conductors may be provided for this purpose. A station may also be provided with a single transmitter and modulating devices for each line leaving the station, the modulations being so selected that each wave only energizes the receiving relay tuned to it at the next station. In an arrangement for parallel-connected lines, Fig. 2, each station is provided with a high frequency transmitter which undergoes a separate modulation for each line section originating from the station. Thus the transmitter at station B transmits wave trains modulated by the arrangements indicated at 13-16, to which receiving relays 130, 140, 150, 160 are tuned at the stations A and C. Similarly, the receivers 110, 120, 170, 180 at station B are tuned to the modulated wave trains emitted from 11, 12, 17 and 18 at stations A and C.