GB360057A - Improvements in or relating to electric protective systems - Google Patents

Abstract

360,057. Protective cut-out arrangements. REYROLLE & CO., Ltd., A., Hebburn-on-Tyne, and ANDREW, T. S., 10, Appletree Gardens, Walkerville, Newcastleon-Tyne. Aug. 5, 1930, No. 23437. [Class 38 (v).] Relates to a protective system for a group of feeders, each with its individual circuit-breakers of relatively small interrupting capacity, all supplied through a group circuit-breaker of large interrupting capacity wherein the tripping of the individual circuit-breaker in the faulty feeder takes place only after the fault has caused the group feeder to open, as in Specification 297,702, [Class 38 (v), Electric switches &c.]. The invention consists in obtaining the correct sequence of operation without the use of field circuits. As shown in Figs. 1 and 2, the main circuit F containing the main overload circuit-breaker G has a branch feeder B containing the feeder circuit-breaker B<1>. The feeder supplies through a current transformer A<1>, a solenoid A having a core C with a lateral pin C<1> normally engaged in a cam-slot D<2> in the core-guide D. With excess current in the feeder due to fault, the core is raised and slightly rotated to bring the pin into line with the vertical slot D<1>. The excess current brings out the main circuit-breaker and the resulting loss of current in the solenoid A causes the core to drop and, through the links E, E<1>, knock out the trip of the feeder circuit-breaker. The group circuit-breaker may reclose after a time interval, automatically, and the feeder circuitbreaker may then be reclosed. The core of the feeder circuit-breaker may be reset with the pin C<1> in the slot by the opening movement of the circuitbreaker itself through a cam-operated lever. In a modification to deal with surges or faults outside the protected feeder, voltage-excited additional coil K<1>, Fig. 4, is used. The core of the coil K, in the raised position, serves to hold a latch lever M, M<1> under a pin J<1> corresponding to the pin C<1>. On fault, the pin J<1> is lifted, the group circuit-breaker opened and the latch lever swung clear, so that the current core may fall and trip the feeder circuitbreaker as before. In the event of a heavy surge, unaccompanied by a collapse of voltage, the pin will be lifted but on falling again will encounter the latch. In the event of a collapse of voltage, due to the tripping of the main circuit-breaker on fault in some other feeder, the current core remains latched in the raised position a projection M<3> on the latch engaging the side of the unraised pin. The current coil may be energized in accordance with the earth-leakage current.