Patent GB-583840-A (GB)
Title: Improvements in electric protecting devices for networks
IPC: H02H1/00
Filed: 1941-12-17
Abstract: 583,840. Protective cut-out systems; electromagnetic switches. COMPAGNIE POUR LA FABRICATION DES COMPTEURS ET MATERIEL D'USINES A GAZ. Dec. 17, 1941, No. 16300. Convention date, Dec. 31, 1940. [Class 38 (v)] In a protective system wherein tripping of an incoming circuit-breaker on external faults is prevented by locking relays energized by carrier currents transmitted from. the outgoing end, the transmission is under control of a directional relay, which is sensitive to the negative and zero sequence currents of power, but susceptible of being made sensitive to the positive sequence power, such as described in Specification 405,531. Starting relays 32, 35 sensitive to phase and earth faults have contacts 32<1>, 35' which normally energize a coil 37" which locks the movement of a directional relay 37 in a stable position, Fig. 4, with contacts 37' closed. A winding 37<111> changes the relay connections so as to make it sensitive to positive sequence power, but is normally short-circuited at contacts 32<111>, 34<111> of relays 32, 34. These contacts also normally short-circuit an auxiliary relay 41 which, in operating, momentarily deenergizes a prolongation locking relay 44 while the winding 37<111> is effecting the above changes, relay 44 being normally in circuit with contacts 40' of a normal locking relay 40. The latter is energizable either from a receiver 43 or from contacts 36' of a relay 36 controlled by relays 32, 35. On external fault, the outgoing relay contact 37' remains closed and, by keeping relay 40 at that end energized, holds the trip circuit open at 40'. At the same time, one or other of contacts 32", 35" is closed to energize 36 which, at 36<111>, removes the short-circuit from a constantly-oscillating modulator 38, which is thus connected at 37' to an oscillator 39, whereby the incoming receiver 43 is energized to hold open the locking relay 40 at that end, and prevent tripping. Further, the outgoing relay 40 energizes the prolonged locking relay 44 which further breaks the trip circuit at 44'. On internal faults, the start relays at each end energize 37" and unlock 37 which open contacts 37' and as relay 36 opens 36', transmission is prevented ; these contacts both open the circuit of relay 40 which thus makes the trip circuit at 40". With symmetrical three-phase faults, contacts 32<111> &c. all open and energize winding 37<111> and relay 41, which prevents any possibility of an unlocking operation of relay 44 until 37<111> has operated, the remainder of the operation being otherwise similar. A modification is also described in which separated-phase switches are conjointly opened on phase faults, whereas by means of further individual phase relays, only the switch of an earth-faulted line is opened. The earth-fault relay 35 has an additional normally-closed contact permitting the discrimination between phase and earth faults, Fig. 5 (not shown). The directional relay spindle 20 carries an arm 21 with magnetic piece 22 cooperating with the poles of a magnet 26 energized by the normally-closed series contacts 32' &c. so as to be immovable until one of the relays 32 &c. operates, Fig. 4.