Patent GB-299813-A (GB)
Title: Improvements in and relating to electrical apparatus for power distribution systems
IPC: H02H7/04
Filed: 1928-11-01
Abstract: 299,813. British Thomson-Houston Co-, Ltd., (Assignees of Gay, F. W.). Nov. 1, 1927, [Convention date]. Systems depending on static transformers; transmission and network conductor arrangements.-To restrict the effects of faults in alternating current systems transformer windings comprise a number of separately insulated coils each connected to a separate load circuit and arranged to provide a low impedance to normal current flow but a high impedance to abnormal currents. In the arrangement shown in Fig. 1 the primary winding has two coils 14, 15 in series, the secondary comprises four coils 6 - - 9, each connected to a separate load, and the core has a member 4 providing a leakage path which becomes saturated at a given load current determined by perforations 5. A short circuit on one secondary winding results in a small decrease in the voltage of the contiguous winding and a small increase in the voltage on the other windings. Alternative arrangements of windings and core are shown in Figs. 2 and 3, the latter comprising a magnetic path in the form of a split ring 32. A transformer similar to Fig. 3 is described with twelve secondaries. Some windings may be parallelled on a single load circuit. Tertiary windings may be added. A distribution network is described in which each secondary is connected through a service conductor to a secondary of another transformer, the primary windings of alternate transformers being connected to one or other of a pair of supply mains. In a switching station interconnecting a number of circuits with three-phase supply mains banks of single phase transformers one bank to each supply main have their independent secondary windings connected through circuit breakers to switching bus bars one for each set of like secondary coils the load circuits being connected to the bus bars through circuit breakers. A synchronizing station is shown in Fig. 7 in which the primary windings of each transformer of a bank are connected in series in one of the phases of a generator 240 and two secondary windings one on each leg of a transformer coil are connected in series in each of the phases of a feeder 255 through a circuit breaker. Each of two tertiary windings is connected through a circuit breaker to one of two synchronizing bus-bars 273, 281, which are provided with circuit breakers for earthing when necessary and from which other feeders as 296 may be supplied through transformers (not shown). A short circuit on either synchronizing bus will double the volts on the other bus but will not greatly affect the voltage on the feeder 255. Fig. 8 shows an alternator 350 with four windings two of which are somewhat displaced in phase with respect to the others. Each transformer comprises four primary windings two on each leg of the core and connected in series with the generator windings as indicated in the Figure. Two secondary and four tertiary windings are provided. The secondary windings are connected both in series with a phase of a feeder 380 and the tertiary windings one to each of four switching bus bars. In all the arrangements described the transformers have a central limb for promoting magnetic leakage under given current conditions in any secondary coil, but these are not necessary in all cases though they serve to maintain equal voltage in all bus bars. Shell type transformers may be used. Reference has been directed by the Comptroller to Specification 16179/04.