Patent GB-422012-A (GB)
Title: Arrangement of connections for the protection of electric transmission lines
IPC: H02H1/00
Filed: 1933-11-29
Abstract: 422,012. Protective cut-out systems. SIEMENS & HALSKE AKT.-GES., Siemensstadt, Berlin. Nov. 29, 1933, No. 33515. Convention date, Jan. 18. [Class 38 (v)] [See also Group XXXVIII] In an arrangement for the constant supervision of alternating currents or high frequency signals of a protective system, preferably superimposed on a power conductor of the section of line being protected, currents or signals are sent continuously or periodically between the beginning and end of the section for supervising the channel, and are simultaneously employed for the transmission of metering values, control orders, conversations, or like signals. In Fig. 1, each of the equipments 1, 2 is similar and 1 comprises a circuitbreaker 103 controlled by contacts 104, 106 of a directional relay 101 and overload relay 102, and by a contact 108 controlled by a coil 109 in circuit with the contact of a relay 110. The winding of 110 is energized by beats produced in an arrangement 111 fed by oscillations from a transmitter 112 and a receiver 113 receiving the oscillations (which differ slightly in frequency from those of 112) generated by a transmitter 212 in the distant equipment. Transmitter 112 is connected to the line by a condenser 114, contact of relay 115, and parallel-connected contacts 107, 116, the latter being controlled by a coil 117 in series with contact 105 of relay 101. Normally, therefore, contacts 108, 208 are kept open by the beats energizing 110, 210 which have large inertia so that they do not release when a momentary cessation of the beats occurs. This cessation is utilized for the transmission of metering signals, and is effected by the relay 115 in circuit with a condenser 118 and contacts of relay 119, the coil of which is in series with a metering transmitter 120. The armature of the latter rotates at a speed such that the frequency of the impulses delivered by it corresponds to the value of the metering quantity to be transmitted, at every instant. At every impulse, relay 119 is actuated and released and thus two impulses flow through 115 which maintains its contact open for a time-interval depending on the time-constant of condenser 118. Thus the connection of 112 to the line is broken during that time-interval and relay 221 actuates the metering-impulse receiver 222. If a transmitter fails, both contacts 108, 208 close, but the breakers are prevented from undesired operation by the fault relays by employing devices 123, 223 which transfer the tripping circuits to time-delayed overload devices. An indication of such failure is given by stoppage of the metering apparatus, but to avoid confusion with genuine faults, the pointer of the metering apparatus is arranged to go below zero when a fault occurs to the right of station 1, 101, 102 respond, whereupon the metering is interrupted at 107, 116, the trip circuits are prepared at 104, 106, and relay 210 allows 208 to close. Disconnection is however dependent on the location of the fault and therefore upon whether 201, 202 perform operations similar to those performed by 101, 102. The Specification gives numerical figures of frequencies employed, and refers also to voice-modulation of the transmitted signals and to the dispensing with the metering-transmission in one direction. In Fig. 2 (not shown), the impulses are superposed on the line by the metering apparatus at a frequency depending on the metered quantity and such that the period of an impulse is not long enough to cause relays 128, 228 to operate. On fault, outside the section, however, impulses are continuously sent by the station where power is outgoing to cause 128 or 228 to open 108 or 208, and so prevent opening of the breaker at the incoming end. With an internal fault, no such impulses are sent, contacts 108, 208 remain closed, and the section is cut out by operation of the overload and directional relays.