The high-speed circuit breaker in railway feeder networks

A method of isolating grounded sections of extensive feeder networks supplying power to railways without disturbing the power supply to other sections has long been desired by railway engineers. This has been successfully accomplished by utilizing the inherent characteristics of the magnetic type of high-speed circuit breakers in the manner described in this article. These characteristics are (a) high-speed operation, (b) discriminating characteristic, (c) reduction in trip point with reduction in line voltage, (d) polarized characteristic. A description of an experimental investigation on an equivalent network for a representative section of feeder system, made up by using reactors and resistors, has been given. Complete selective operation, isolating defective feeder without disturbing the power supply to interconnected feeders, was obtained for all locations of the short circuit. Breakers of the type used successfully on d-c. networks can be applied to a-c. networks and the advantages of high-speed protection realized on this type of system. High-speed operation is very effective in reducing telephone interference during short circuits on the a-c. railway system.