Patent GB-426958-A (GB)
Title: Improvements in or relating to protective arrangements for sectionalised electric power circuits
IPC: H02H7/26
Filed: 1933-10-12
Abstract: 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 D<4> .. D<6> and low-current setting contacts D' .. D<9>, suitable constructions being those described in Specification 391,135. The directional stabilizing relay C has normally-closed contacts C<4> .. C<6> 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 C<1>, C<3>, D<1>, D3 are responsive to interphase faults and C2, D<2> to earth faults. Contacts D<4> .. D<6> in parallel control an auxiliary trip relay E, the contacts E4, E<5> of which normally connect telephones or other auxiliary apparatus O to the pilot K, K<1>. Energization of E however disconnects O and closes E<1>, E<2> to connect the coil of lock-out relay H to the pilot, and closes E<3> 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 C<4> .. C<6> and D<7>, D<8>, D<9>, providing three parallel circuits with normally-closed contacts D<12>, 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 D<8> or D<9>, and provided C<4> .. C<6> remain unoperated, F makes at F<3>, 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 C<1>, D<1>, of relays C, D will operate, the former being energized by closure of D<10> and opening its contacts C<4> to prevent F from being energized by closure of D' and sending the stabilizing current, and the latter closing D<4> to energize E and by closure of E<3> to start the time-lag relay G. If the fault is fed from the remote end also, d<1> closes d<7>, d<10> and energizes c<1> which opens contacts c<4> to prevent f from sending the stabilizing current. Subsequent closure of d<4> energizes e which closes e<3> 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, c<1> is not operated by closure of d<7>, d<10>, so that the circuit of f is made at d7 and battery n is connected over f<3>, f<4> to the pilot and H and over el, e<2> 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 j<1>, j<2>, 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 B<6>, B<7> being provided in the respective trip-coil circuits. The H.F. transmitter and receiver P, having an indicator P<4>, is connected to a line by means of a tapping on a coupling condenser P<1> having a safety spark-gap P<2>. The transmitters may operate on the same or on different frequencies. The high-current contacts D<17> .. D<19> of the trip relay D<13> control directly the time-delayed relay G<4> over contacts H<3> of a lock-out relay H<2> and contacts F<8> of an auxiliary stabilizing relay F<5>. The relay H2 is energized by closure of contacts P<3> by the H.F. receiver on receipt of a stabilizing signal. Relay F<5>, on operating due to fault power flowing out of the section, opens F<8> to prevent tripping at the home end and closes F<6>, F' to connect battery N<1> to the transmitter for sending a stabilizing signal to the remote end. A phase and earth-fault indicator J<5> 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.