Patent GB-174971-A (GB)
Title: Automatically reclosing electric circuit breakers
IPC: H02H3/06
Filed: 1920-09-02
Abstract: 174,971. Raney, E. C. Sept. 2, 1920. Protective arrangements; automatic circuitbreakers.-An automatically-resetting sectionalizing circuit-breaker for connecting and disconnecting two feeder sections, each of which mav be energized from an independent source or both supplied from either end as a single feeder opens on overload, short-circuit, or voltage failure on either section and does not reclose as long as there is a short-circuit on either section or abnormally low voltage on both, but recloses when the short-circuit is removed from one section provided there is sufficient voltage on the other section, equally whether both sections are being independently fed or one section only. The gap between the sections is bridged by a resistance so connected that a given circuit passing therethrough will produce the same potential on the closing means when a given potential is applied to either section. As shown in Fig. 1, the ends of the sections A, B are connected through the coil 8 of the overload element of the circuitbreaker to the contact terminals 3, 2, which are bridged by the contact-member 1 actuated through a linkage mechanism by the plunger 5 energized by the voltage coil 4. The ends of the sections are also permanently interconnected by equal resistances 21, 22 in series. The voltage coil 4 is energized by a circuit extending from the middle point 23 of the resistances through the normallyclosed contact-arm 7 of the overload element to the fixed contact 26, thence to the fixed contact 2 (with which a contact arm 10 engages when the circuit-breaker is in the " off " position), through the resistance 20 to the contact arm 10 and finally, through the coil 4 to the return feeder or to earth. With the circuit-breaker closed, as shown, in the event of overload or short-circuit on either section, an excess current will pass through the coil 8, and the holding-on circuit through the coil 4 will be interrupted at the contacts 7, 26, whereupon the circuit-breaker will assume the off position shown in Fig. 2. When normal current conditions are restored, contacts. 7, 26 re-engage; the current through the coil 4, while adequate as a holding-on current, is insufficient to bring the circuit-breaker to the closed position until the resistance 20 is short-circuited by the closure of the contact arm 10 on to its contact 13. The arm 10, however, is locked in the off position by the latch 15, which is raised by the plunger 17 energized by the coil 16 from the resistance point 23 through the resistance 32 and through a retarded switch 18, 35 which begins to close slowly as soon as it is released by the fall of the main plunger 5, when the circuitbreaker assumes the " off " position. The setting of the coil 16 is made greater than 50 per cent of the normal line potential so that whenever the potential on one section is approximately normal and no short-circuit (or very low resistance which would involve a heavy overload) exists on the other section, the switch arm 10 will be released to short-circuit the resistance 20. If the predetermined interval since the opening of the circuit-breaker has elapsed, as imposed by the retarded switch 18, 35, the coil 4 will be sufficiently energized to carry the circuit-breaker to the closed position. Just before the closed position is reached, an arm 14 opens the switch 10, 13, reinserting the resistance 20 and reducing the current in the coil 4.