Patent GB-208542-A (GB)
Title: Protective arrangements for electrical installations
IPC: H02H7/26
Filed: 1923-12-12
Abstract: 208,542. Modigliani, U. Dec. 14, 1922, [Convention date]. Cut-out arrangements; electric-motor actuation; induction relays.-In protective systems for parallel feeders, the relays controlling the operation of the automatic circuit-breakers are so arranged that upon a disturbance of balance the relay on the affected feeder, while operating, prevents or blocks the action of the relays in corresponding phases of parallel feeders or of all other relays in the system. As applied to a three-phase system in which bus-bars I, II, III at the generating station G, Fig. 1, supply similar bus-bars at a distant generating station F, Fig. 2, through three parallel feeders L1, L2, L, the feeders are provided with circuit breakers A1, A2, A3 at each end controlled by trip coils B1, B2, B3. In each phase of each feeder is included a relay either directly as shown in Fig. 1, in which relays 1<1>, 1<11>, 1<111>, 2<1>, 2<11>, 2<111> and 3<1>, 3<11>, 3<111> are included in the phases of feeders L1, L2, L3 or through series transformers, as shown in Fig. 2, in which corresponding relays are fed through series transformers T,', T1<SP>11>, T1<SP>111>. T2<SP>1>, T2<SP>11>, T2<SP>111> and T3<SP>1>, T3<SP>11>, T3<SP>111>. Relays for corresponding phases of the different feeders are grouped together as shown in Fig. 3 in which the first or right-hand comprises relays 1<1>, 2<1> and 3<1>, the other groups being similarly constituted. Each relay consists of an induction disc driving member consisting of a disc 10, braking magnet 13 and driving electro-magnet 12 which may produce a torque corresponding to the current or to the power in the corresponding phase of the feeder. The disc 11 is mounted on a vertical shaft 10 in two parts which are connected by a sliding coupling 16. The upper part of the shaft 10 carries a worm 17 which drives a toothed wheel 21, the drive being non- reversible. The toothed wheels 21 corresponding to each group of relays are mounted on a common shaft D to which they may be secured by ele,ctromagnetic clutches D<1>, D<11>, D<111> operated by corresponding feeder phase currents. During normal operation of the feeders each relay of a group tends to rotate the shaft D at the same speed and a certain speed of the shaft is accordingly obtained. If excess current or power occurs on any one feeder phase the increase of torque on the corresponding relay shaft is ineffective to increase the speed of the shaft D, but causes the upper portion of the shaft 10 to rise. A corresponding contact C<1>, C<11> or C<111> is thereby engaged and the circuit of the corresponding trip coil B1, and B2, B3, completed, the corresponding circuit breaker subsequently opening instantaneously or after a predetermined time interval. The contacts C<1>, C<11>, C<111> also close the circuits of blocking electromagnets M<1>, M<11>, M<111> with corresponding armatures H<1>, H", H<111> which by rotating shafts H<1>, H<11>, H<111> cause detents to engage stops 18 on the shafts 10 of all the relays of similar phase other than the one which has operated, so preventing their operation while the faulty feeder is being cut out. The value of excess current which may operate any relay may be adjusted by the value of a weight 19 secured on the upper portion of the shafts D. In modified' forms of the invention the relays may be operated by reverse current and the system may be applied to direct current supply, the relays being driven by motors having suitable characteristics.