Patent GB-522738-A (GB)
Title: Improvements in and relating to systems of electrical distribution
IPC: H02J3/38
Filed: 1938-12-14
Abstract: 522,738. Electricity supply; transformers. BRITISH THOMSON-HOUSTON CO., Ltd. Dec. 14" 1938, No. 36463. Convention date, Dec. 14, 1937. [Classes 38 (ii) and 38 (iv)] Distribution network arrangements; transformer arrangements.-In a system of electrical distribution the secondary of a transformer is connected to a load circuit and a plurality of primary windings of the transformer are each connected to a different voltage source, the winding arrangement being such that equal ampereturns are supplied by each of the primary windings to the load. The different voltage sources may be generators or the different windings of double or multiple winding generators and in either case they may be connected to the different sections of a busbar system sectionalized by reactances so that the system ensures balance of the currents supplied from the different sources. In Fig. 1 four sections 11, 12, 13, 14 of a busbar system 10 of the ring type (shown single-line) are separated by sectionalizing reactors 15, 16, 17, 18 and fed by generators 19, 20, 2'1, 22, respectively. Sectionalizing switches are referred to. Feeders 2'3, 24 are fed respectively from the high-voltage secondaries 26, 30 of balancing transformers 25, 29 which are similar, each having two primary windings connected -to different sections of the busbar system. In the balancing transformer winding diagram, Fig. 2, 38 and 39 are the primary windings on different legs while the secondary winding 40 comprises two windings, one on each leg, in series. With equal numbers of turns in each of these secondary winding sections, equal amp.- turns are supplied from each of the primary windings. Separate magnetic return paths 36 and 37 are provided for each of the winding legs. In an alternative core structure Fig. 4 (not shown) additional magnetic return paths are provided. In an alternative winding arrangement Fig. 3 (not shown) the windings are carried on the outer legs of a three-legged core, the central leg of which forms a common magnetic return path. With these arrangements, in the event of a short-circuit on one of the primary supply circuits, the current fed to it from the other is limited by the high reactance introduced by the loose magnetic coupling between windings on different legs. In Fig. 5 (not shown) doublewinding generators each have one of their windings connected to one busbar system and the other winding to a different busbar system. The two busbar systems are interconnected by reactors and each feeder is coupled to both systems through a balancing transformer of the type described above. In Fig. 6 (not shown) double - winding generators feed a ring - type busbar system like that 'in Fig. 1, and full three-phase connections are given. There are two sectionalizing reactors between the separate windings of a given generator and at least one between windings of different generators. Three single-phase balancing transformers are employed but in Figs. 7 and 8 (not shown) winding diagrams for three-phase transformers are shown. Specifications 311,344, [Class 38 (iv)], and 366,184 are referred to.