426,958. Protective cut-out systems. REYROLLE & CO., Ltd., A., Hebburn-on- Tyne, and LEYBURN, (formerly LEBEN), H., 212, Wingrove Road, Newcastle-on-Tyne. Oct. 12, 1933, No. 28172. [Class 38 (v)] In protective arrangements for sectionalized circuits of the kind disclosed in Specifications 314,778, [Class 38 (v)], and 391,134, in which each section is protected independently of the others and a trip relay device at one end acts to trip the adjacent breaker unless prevented by a stabilizing current transmitted from the other end when power current is flowing out at such other end, a stabilizing current is transmitted from one end on operation of the trip relay device at that end unless such transmission is prevented by the opening of normally-closed contacts of a stabilizing relay device responsive to the direction of flow at the said end. In the pilot-circuit system shown in Fig. 1 as applied to a section of a ring main, similar apparatus is employed at each end, that at the " home end being denoted by capital, and that at the remote " end by corresponding small, reference letters. The trip relay D is non- directional and has high-current setting contacts D4 .. D6 and low-current setting contacts D' .. D9, suitable constructions being those described in Specification 391,135. The directional stabilizing relay C has normally-closed contacts C4 .. C6 adapted to open with incoming power, and potential coils energized from a transformer M and current coils energized, along with the coils of D, from current transformers in the lines, the connections being such that C1, C3, D1, D3 are responsive to interphase faults and C2, D2 to earth faults. Contacts D4 .. D6 in parallel control an auxiliary trip relay E, the contacts E4, E5 of which normally connect telephones or other auxiliary apparatus O to the pilot K, K1. Energization of E however disconnects O and closes E1, E2 to connect the coil of lock-out relay H to the pilot, and closes E3 to connect the timedelayed trip relay G to the local battery N over closed contacts of H. An auxiliary stabilizing relay F is connected across battery N in circuit with contacts C4 .. C6 and D7, D8, D9, providing three parallel circuits with normally-closed contacts D12, the function of which is to open and ensure disconnection of an earth fault in the section when, with a simultaneous interphase fault outside the section, a stabilizing current would otherwise be transmitted. When energized by closure of D' or D8 or D9, and provided C4 .. C6 remain unoperated, F makes at F3, F' a connection from N to the pilot. In operation, if fault power enters the section at the home end, one or other of the elements, say C1, D1, of relays C, D will operate, the former being energized by closure of D10 and opening its contacts C4 to prevent F from being energized by closure of D' and sending the stabilizing current, and the latter closing D4 to energize E and by closure of E3 to start the time-lag relay G. If the fault is fed from the remote end also, d1 closes d7, d10 and energizes c1 which opens contacts c4 to prevent f from sending the stabilizing current. Subsequent closure of d4 energizes e which closes e3 to start the relay g. As no stabilizing currents are transmitted, H, h remain unoperated so that the section is cut out when the time-lags of G, g have expired. If the fault power flows out at the remote end, however, c1 is not operated by closure of d7, d10, so that the circuit of f is made at d7 and battery n is connected over f3, f4 to the pilot and H and over el, e2 to h. Thus H, h are both operated to prevent cutting out of the section. If no fault power flows past the remote end, no operation of c, d occurs and no stabilizing current is sent therefrom ; G therefore trips the home breaker. Phase and earth-fault indicators, as j1, j2, respectively, are provided and operated by the appropriate contacts of the tripping relays. Fig. 2 shows the invention as embodying superimposed high-frequency stabilizing currents for protecting a section including a T-off connection from the home end of the ring main section, manual switches B6, B7 being provided in the respective trip-coil circuits. The H.F. transmitter and receiver P, having an indicator P4, is connected to a line by means of a tapping on a coupling condenser P1 having a safety spark-gap P2. The transmitters may operate on the same or on different frequencies. The high-current contacts D17 .. D19 of the trip relay D13 control directly the time-delayed relay G4 over contacts H3 of a lock-out relay H2 and contacts F8 of an auxiliary stabilizing relay F5. The relay H2 is energized by closure of contacts P3 by the H.F. receiver on receipt of a stabilizing signal. Relay F5, on operating due to fault power flowing out of the section, opens F8 to prevent tripping at the home end and closes F6, F' to connect battery N1 to the transmitter for sending a stabilizing signal to the remote end. A phase and earth-fault indicator J5 is provided. Unlike Fig. 2, the protection zone of Fig. 1 does not include the breakers, so that back-up protection apparatus may be provided to deal with faults occurring in such parts of a section. If desired, trip relays may be employed that close all their contacts for the same operating current.
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