GB221322A - Improvements in or relating to electric distribution systems - Google Patents

Abstract

221,322. Electrical Improvements, Ltd., and Beard, J. R. July 27, 1923. Protective arrangements.-In a duplicate supply substation in an electric distribution system, in order to reduce the number of circuit-breakers and to improve the protection, which may be of the. Merz-Price type, the usual substation bus-bar is dispensed with and the incoming feeders are connected together by a high-tension circuitbreaker, while the outgoing low-tension feeders are connected, through one or more transformers and through fuses or switches of comparatively 1 low rupturing capacity, to the opposite sides of the high-tension switch. As shown in Fig. 1, applied to a sub-station A receiving power from duplicate feeders B, B<1> from similar substations A<1>, A<2> and supplying low-tension power from duplicate transformers E, E<1>, the two feeders are connected together through the high-tension circuit-breaker C and are also respectively connected through fuses D, D<1> to the two transformers E, E<1>. Low-tension circuit-breakers F, F<1> are provided in the low-tension supply circuits. Protection is obtained by current transformers G, H, G', H<1>, located where shown in the substation and normally balancing against similarly located current transformers in the other two stations. Thus, feeder B is protected by means of a pilot circuit controlled from four current transformers respectively at the points G, H in the substation A and the corresponding points G, H in the substation A<1>, the circuit-breaker C and the fuse D together with the corresponding apparatus in the substation A<1> being included in the protection. Where duplicate transformer supply is not needed, a two-way switch, which may automatically change-over on failure of the consumers supply, may be used to connect the transformer through one of two fuses to the high-tension feeders. In the arrangement shown in Fig. 3, a single transformer E and a single fuse D are employed in conjunction with the two-way switch J. A single current-transformer G, G<2> replaces the transformers G, G<1> of Fig. 1 and this transformer is connected up by means of the changeover switch K interlocked with the two-way switch J, to one only of the pilot wire circuits L, L<1> viz. that protecting the feeder section to which the transformer E is connected through the switch J.