Arrangement in electric switch stations

摘要

755,585. Air break switches; automatic circuit breakers. ALLMANNA SVENSKA ELEKTRISKA AKTIEBOLAGET. Sept. 20, 1954 [Oct. 22, 1953], No. 27125/54. Class 38(5) In order to prevent the unintentional closure of a circuit by closing of pneumatically-opened breaker contacts 2, 3 by spring pressure due to a decrease of the air pressure, a normally-closed disconnecting switch 11 is operated to open before the breaker contacts close when the pressure falls below a certain limit. The switch 11 is operated by a rod 12 locked in position by a pawl 16, and, when the pressure drops in supply pipe 8, contacts 26, 29 close, contacts 30, 31 being already closed due to full air pressure in pipe 10, thus completing a circuit through contacts 31, 29 and the coil of an electromagnet 33. which attracts the pawl 16 thus allowing spring 13 to open the switch 11. On restoration of the air pressure in pipe 8, contact 26 closes contacts 27 thus completing a circuit over contacts 28, and coil 19 of a compressed-air valve 18, and causing the armature 20 to open valve 18 so that air from pipe 17 flows into cylinder 14 and piston 15 moves rod 12 downwards until pawl 16 engages shoulder 32 on the rod. The disconnect switch is prevented from opening when the breaker is closed since valve 9 is closed and pipe line 10 is not under pressure, so that the contacts 31 are open and there is no circuit to the electromagnet 33. In the case of switchgear where the disconnect switch opens every time the braker opens, the switch is arranged to be locked open in case of a decrease in the air pressure.