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AssigneeSiemens Aktiengesellschaft
InventorsKlaus Bollmann, Hans-Joachim Freygang, Jurgen Moeller, Manfred Weniger
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Disclosed are an inductive voltage transformer having a primary winding connected to a network line and a protective circuit therefor. In order to prevent a large thermal and mechanical stress in such a transformer, the protective circuit comprises a control unit which controls a switching device for connecting a circuit arrangement to a secondary winding of the voltage transformer. The circuit arrangement includes a current generating circuit with a charging capacitor. The protective circuit operates to generate a current causing a counter excitation in the transformer to that caused when the capacitance of the network line is discharged via the primary winding of the transformer. The voltage transformer and the protective circuit are suited particularly for connection to network lines having a large internal capacitance.
Apparatus for connection to an inductive voltage transformer having a primary winding connected directly to a network line and at least one secondary winding connected a load, the apparatus comprising control means connected to the transformer primary, switching means connected to the control means, and means for generating current, the control means controlling switching of the switching means, the switching means coupling the current generating means to a secondary winding of the voltage transformer, the switching means providing a low impedance between the transformer secondary and the current generating means responsive to the control means, whereby current fed to the transformer secondary from the current generating means causes an excitation opposed to the excitation caused by the discharge of a capacitance associated with the network line through the transformer primary winding.
In a voltage transformer having a primary winding connected to a network line, the improvement comprising apparatus connected to the transformer for causing an excitation in the transformer opposed to the excitation caused by a discharge of the capacitance of the line through the primary winding of the transformer, the apparatus comprising control means connected to the transformer primary, switching means connected to the control means, and means for generating current, the control means controlling switching of the switching means, the switching means coupling current generating means to a secondary winding of the voltage transformer, the switching means providing a low impedance between the transformer secondary and the current generating means responsive to the control means whereby current fed to the transformer secondary from the current generating means causes an excitation opposed to the excitation caused by the discharge of a capacitance associated with the network line through the transformer primary winding.
Dependencies are inferred from the claim text.