GB629829A - Improvements in or relating to saturable reactor stabilising arrangements for a.c. systems - Google Patents

Abstract

629,829. Protective arrangements ; transmission line arrangements. GENERAL ELECTRIC CO., Ltd., and FRIEDLANDER, E. S. Oct. 27. 1947, No. 28629. [Class 38 (iv)] To minimize or suppress harmonics, particularly the fifth and seventh, in a stabilizing arrangement of of the A.C. or D.C. saturable reactor type for a three-phase electric supply system, a second harmonic accepter filter is associated with the reactors, which are arranged in two groups, each comprising three star- or interstarconnected reactors provided with a magnetic leakage path, the two groups being so connected to the A.C. system that there is a relative phase displacement of 30 degrees in their magnetic fluxes. The two groups may be connected together in parallel, series or cascade. In the arrangement shown in Fig. 1, groups 2, 3 of reactors 1 are connected across a three-phase line 4 which is also shunted by three starconnected second harmonic filters 9, 10. The reactors of each group are interstar-connected and their line connections are such that the fluxes in the two groups lead and lag, respectively, by 15 degrees the flux which would obtain with a simple star connection. The windings 10 of the second harmonic filters may be wound one on each limb of a three-limbed core having air-gaps distributed over each limb. The filters may be connected to interstar-connected secondary windings on one of the reactor groups instead of directly shunting the line 4 ; or a single filter connected across two phases may replace the star-connected arrangement shown. The windings of each reactor group may be accommodated on a three-limbed core 6, Fig. 2, having magnetic shunts 7 which may be provided with air-gaps so dimensioned as to suppress the eleventh harmonic or to reduce both the eleventh and thirteenth harmonic. This reduction may also be effected, instead of by air-gaps, by providing on the individual cores of the reactors secondary windings which are connected in open mesh to reactors of appropriate magnitude. The arrangement may be used to protect a meshconnected transformer against possible harmonic instability, by connecting the arrangement in parallel with the transformer and operating the reactors at a higher flux density than the transformer. Specification 610,061 is referred to.