GB191104004A - Improvements in or relating to Electric Current Distributing Systems. - Google Patents

Abstract

4004. Merz, C. H., and Hunter, P. V. Feb. 16. [Cognate Application, 5189/11.] Protective arrangements.-Relates to the protection of distribution networks of the type in which each section is composed of leads connected in parallel and provided with automatic circuit-breakers acting at both ends of a section in the event of leakage from a faulty lead. The invention, which is particularly applicable to ring-main networks, consists in arranging and combining the leads of a section in such manner that leakage from one lead produces an inductive disturbance which assists the action of all the circuit-breakers of the section. According to one form of the invention, shown in Fig. 1, windings c, d at one end of each lead a, b of a section A are combined on a magnetic core e, which is adapted to open a switch i when an algebraic or vectorial difference of currents arises in the two leads due to a leak from one of them. A similar arrangement is put at the other end of the section and the various branches thereof. The several windings are designed as impedance coils to augment the different currents at the end remote from the leak, and the two leads are disposed so as to have mutual induction for the purpose of augmenting the difference at the end adjacent to the generator. In an arrangement adapted for alternating currents, the core of the impedance windings is provided with an additional normally idle winding to actuate the circuitbreaker, and a relay coil is connected across equipotential points of an auxiliary circuit energized by series transformers, the two leads being disposed mutually inductively. In the arrangement shown in Fig. 9, an impedance device 3 is provided separately from the circuitbreaker operating means. The mutual induction of the leads may be obtained by placing them side by side in specially constructed cables. As shown in Fig. 8, the two leads may be mounted on overhead supports, and crossed or spirally related so as to eliminate unequal inductive effects from outside conductors, the two wires being kept apart by insulating-sleeves r' and struts r'.