GB587881A - Improvements in line drop compensation of voltage regulators for alternating currentpower circuits - Google Patents

Abstract

587,881. Automatic control systems for electric supply. BRITISH THOMSON HOUSTON CO., Ltd. May 31, 1943, No. 8692. Convention date, May 29, 1942. [Class 38 (iv)] Voltage.-Regulators in separate circuits jointly supplying a load through a common line are compensated in respect of line drop and circulating current by means responsive to these values independently. Fig. 1 shows regulators 4 ... 7 for coils of three delta-connected tapchanging transformers supplying a load circuit 3 wherein current transformers 12 supplying the compensating circuits of the regulators are associated with a zig-zag transformer 13 and polyphase reactor 14 which, as regards any circulating current, have respectively low and high reactance. In consequence, all zero sequence, or circulating current, components flow through the compensating transformers 10 and all positive sequence currents flow through the line drop compensators 11. Relays 9 disable the regulators with conditions of excessive circulating current. Fig. 3 shows three parallel connected circuits 21 ... 21<11> which supply a common load by connections not shown. Auxiliary close-coupled current transformers 22 have their secondaries connected in series in a closed circuit so that the whole of the circulating current components are forced to flow through the compensating transformers 10 and effects of circulating current are neutralized. In a modified arrangement (Fig. 4, not shown), the transformers 22 used are no less than the number of paralleled circuits 21.