Bbc Brown, Boveri & Company, Limited

Gerhard Linhofer

Kadry Sadek

Georg Koppl

Leopold Blahous

Niyazi Ari

Gerhard Guth

Josip Dobsa

Walter Kuhn

Absorption circuits (C.sub.f,L.sub.F) are used for filtering out unwanted harmonic currents in electric lines (R, S, T), particularly for rated power within the range of 1 MVar-1 GVar, for example in the case of high-voltage direct-current transmission systems. So that the absorption circuit holds the virtual capacitance of the filter capacitor circuit (C.sub.f) at its rated value at a tuned frequency even when one or more capacitors (C11, C21, C12, C22) fail, a compensating choke (L) is provided in the cross branch of an 'H' circuit of the capacitors. The capacitance of each capacitor (C11 . . . C22) is equal to the total capacitance C of the filter capacitor circuit (C.sub.f). The inductance L of the compensating choke (L) is equal to 1/.omega..sup.2 C, where .omega.=angular frequency of the harmonic. The compensating choke (L) can be designed for 5%-10% of the power of the filter choke (L.sub.F). Instead of in the cross branch, the compensating choke can also be connected between two series-connected capacitors (C12, C 22) in series with these capacitors.

Absorption circuit

Where different 3-phase systems are connected to each other via two static converters having an intermediate direct-current circuit, the exchange of power via the intermediate direct-current circuit can be interrupted by a severe disturbance, for example by failure of a static-converter or by line or busbar faults causing a short-circuiting of one of the static converters. This interruption means a change in the balance of effective power and, associated with this, a shedding of reactive load for the other undisturbed 3-phase system. To reduce high dynamic overvoltages which can lead to plant components being endangered or to operational disturbances, the firing angle of the static converter remaining in operation is regulated with dependence on the alternating voltage of the alternating-current system connected to this static converter, in such a manner that the overvoltage is reduced. This is carried out by regulating the current. The firing angle can be adjusted simultaneously with the short circuiting of the intermediate direct-current circuit by means of a short circuit device.

Method for reducing dynamic overvoltages in an alternating-current

Phase shifters are used in meshed, multi-phase power supply systems for improving their transmission stability and for load-flow regulating purposes. In order to be able to use a less costly exciter transformer of lower rating or the tertiary or compensation winding of a system coupling transformer for generating intermediate-circuit voltages as a function of system input voltages, a resonant circuit is provided between the exciter transformer and an auxiliary transformer. In this resonant circuit consisting of series-connected capacitors and inductive resistances which are connected to taps between these capacitors and can be switched in and out by means of alternating-current switches, tap voltages are generated which are supplied to the primary windings of the auxiliary transformer. At the secondary windings, connected in series with phase conductors of the auxiliary transformer, auxiliary voltages occur which are superimposed on the system input voltages and effect the desired phase shifts. Instead of air chokes which can be switched off, chokes with a ferromagnetic core or the impedance of a transformer, the secondary winding of which can be short-circuited by means of an alternating-current switch, can also be used as variable inductive resistances in the resonant circuit. The inductive resistances can also be star-connected instead of delta-connected.

Phase shifter

A better filtering effect for disturbing harmonic currents in a high-tension direct current transmission installation is described. A balancing winding is provided between a primary winding as an outer winding and a secondary winding in a 3-winding transformer with a transformer core. The distances between the balancing winding and the primary winding and the secondary winding, respectively, are selected such that the equivalent reactance of this balancing winding is equal to or less than zero. A second balancing winding can be provided as the inner winding in a series with the first balancing winding. In the case of a 4-winding transformer, two winding arrangements are provided with two parallel-connected primary windings as the outer windings, with a separate secondary winding for each and a balancing winding for each between the primary and secondary windings, the two balancing windings being connected in series.

Static converter transformer with harmonic filter

A coolable electrical component having a housing (1) filled with insulating gas, and a conductor (2) of hollow cylindrical construction causing a high voltage, arranged in this housing (1). Through the interior space (7) of the conductor a coolant is circulated. The electrical component occupies a smaller space and yet allows increased current load capacity. This is achieved by providing a high-pressure tank (19) extending in the longitudinal direction of the conductor (2) in the interior space (7) thereof. The tank is connected to a gas liquefaction installation by means of outlet orifices (18) perforated in its wall at regular intervals thereof. Such a componet may preferably be a tubular gas cable or a component of a gas-insulated, metal-encapsulated switchgear.

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Baden, Switzerland

Gerhard Linhofer