Abridgment of automatic reclosing high-speed circuit breaker feeder equipment for D-G railway service

High-speed circuit breakers have been used in both feeder and machine circuits of railway substations. It is the purpose of this paper to point out some of the advantages gained by placing this type of breaker in the feeder circuit and also to describe some of the more common types of feeder equipment using a well-known form of high-speed circuit breaker. A brief summary of the breaker characteristics is given, together with the results of short-circuit tests made on 600-volt reclosing feeders employing this type of breaker. The reclosing action is ordinarily obtained by means of a relay which, in conjunction with a load indicating resistor, measures the resistance of the external circuit. In order to permit feeder conditions to reach a stable value and particularly to enable all transient and counter e. m. f. effects to disappear before the reclosing devices are given control after the opening of the breaker, the action of this relay is purposely delayed. The latter effects usually disappear within a few seconds of the opening of the breaker on the usual type of railway circuits. In a majority of cases a time delay of 10 to SO seconds (after the opening of the breaker) elapses before the reclosing devices are given the control of the breaker. After this time delay has expired and load conditions have reached the desired value, the circuit breaker is reclosed. In some cases, especially for sectionalizing purposes, it has been found satisfactory to take the reclosing indication and control from the load side of the breaker. This feature requires that some other breaker undertake the reestablishment of voltage on the load circuit. By means of supervisory control the range of such equipment can be extended so as to pick up a dead section during abnormal operating conditions. A majority of 3000-volt installations has been made in connection with main line electrification where the desired reclosing operation is a combination of load-indicating and load-limiting functio- s. Voltage increments on the load of too large a value may increase the tractive effort to such values as to cause wheel slippage of the locomotive, or snapping of draw-bars; consequently the load voltage is raised in graduated steps by progressively short-circuiting portions of load-limiting resistors placed in the feeder circuit.