Patent GB-416562-A (GB)
Title: Improvements in and relating to systems of electric distribution
IPC: H02J3/38
Filed: 1932-12-16
Abstract: 416,562. Automatic regulation; phase changing. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London.- (Assignees of Alexanderson, E. F. W. ; 8, Adams Road, Alger, P. L. ; 1758, Wendell Avenue, and Nixdoref, S. P. ; 18, Hampton Avenue, all in Schenectady, New York, U.S.A.) Dec. 16, 1932, No. 35752. Void [Abridged as open to inspection under Sect. 91 of the Acts, June 17, 1933]. [Classes 38 (ii) and 38 (iv).] Equalizing load on generator.-In a transmission system interconnecting synchronous machines, instability resulting from transient disturbances is prevented by periodically connecting a power absorbing circuit to a generator in dependence on the phase relation between the voltage vector of the generator and a selected time-phase voltage vector of reference, such as that of the transmission system. The average load current in the power absorbing circuit is dependent upon the phase displacement and the system operates to maintain a fixed angular relation or to effect readjustment to steady state conditions during transient departures from synchronism. Preferably a resistance load is connected to the generator by vapour electric valves operating at a point lying at the boundary between a fully conductive and a non-conductive condition, and a regenerative connection between the resistance load and the grid circuit of control valves produces a periodic oscillation between these conditions. A single phase arrangement is shown in Fig. 1 in which a synchronous generator 1 is connected through a long transmission line 2 to synchronous machines 3 and a transformer 8 is connected through a full wave rectifying connection of grid controlled vapour discharge devices 6, 7 to an auxiliary load circuit 5. The grids are supplied with control potential from an impedance phase shifting circuit comprising a saturable inductance 13 and a resistance 14 which is energized from the transmission line through a transformer supplied from a phase retarding circuit 11, 11<a>. The saturating winding of the inductance 13 is connected across an adjustable portion of the load circuit 5. In normal conditions the vector OD representing the potential applied to the transformer 9 is opposed to the vector OA representing the potential of the generator and transmission system and the valves 6, 7 are nonconducting. When the phase of the generator potential advances to a position such as OA<1> due to a transient or to the opening of the circuit breaker 4 the valves immediately become fully conducting. The vector OD results from the maximum reactance of the reactor 13 which is reduced as soon as current is established in the resistance 5 and in the saturating winding 15. The vector thus swings to a position OD<1> in which the valves are nonconducting and an oscillation is set up which produces an average loading of the generator by the resistance 5 tending to maintain the generator potential in phase with that of the transmission system or of that portion of it to which the pilot wires are connected. In a modification for a polyphase system resistances are connected in star across the generator bus through reversely connected grid controlled power valves the grid circuits of which are energized from the generator bus through control valves. The grids of the latter are supplied with potential automatically varied in phase to cause the valves to oscillate between full conductivity and nonconductivity. This grid potential is derived through single-phase pilot wires from the distant end of the transmission line through an impedance phase shifting circuit comprising the elements 13, 14 of Fig. 1, a single to polyphase conversion and an adjustable polyphase phase changing transformer. The saturating winding on the reactor of the impedance circuit is connected across an auxiliary resistance the current in which is caused to vary in accordance with the current in the load resistances, being fed from the generator bus through rectifier valves, grid controlled from a series transformer in circuit with one of the load resistances.