GB269852A - Improvements in excess current protective devices, more particularly for unattended power stations - Google Patents

Abstract

269,852. Akt.-Ges. Brown, Boveri, et Cie. April 26, 1926, [Convention date]. Cut-out arrangements.-In an automaticallyreclosing circuit-breaker system, when, on fault, the circuit-breaker a is tripped it closes back contacts c, d the first of which closes the circuit of a motor m from an auxiliary source h whereupon the motor drives a set of commutators e, f, g, which time the reclosure which is effected only if the short-circuit testing relay n is closed. The relay which under the control of the protective relay s is connected across the circuit-breaker (in series with a resitance r) opens when a complete short-circuit exists on the line. When the circuit-breaker opens on fault, the back contacts d close and a circuit from the auxiliary source is completed through the cam 1 and the cooperating fixed contact of the cam disc e to the protective relay s. This closes and connects the relay n across the circuit-breaker. If this relay remains closed (indicating no complete shortcircuit) the reclosing relay o is closed when, a few seconds after, the cam 1 of disc f engages its fixed contact. The closure o relay o completes the reclosing circuit o the circuit-breaker and if the overload (although not a complete short-circuit) is too heavy, the circuit-breaker is tripped again and again reset. This continues four times, after which the last cam disc energizes a blocking relay i (which must be reset by hand) and further reclosure is prevented. The cam discs return under the action of the spring k.