| 摘要 |
Apparatus for generating a signal indicative of a fault occurring in an AC electric circuit connected to an AC network (UW). The AC circuit (1) comprises a series connection of at least one inductance winding (L) and a two-way static switch having thyristors (5, 6) controlled by firing pulses theta , and the capacitive impedance and the resistive impedance of said AC circuit are negligible relative to its inductive impedance L. The apparatus comprises a differential relay (15) receiving first and second input signals and providing an output signal (Id) when said input signals are unequal. The first input signal is a real image of the current flowing through said AC circuit as provided by the secondary winding of a current transformer (30) inserted in said AC circuit. The second input signal is a theoretical image of the current flowing through said AC circuit as provided by a theoretical image signal generator (16) which generates the theoretical image signal as a function of the said inductive impedance L, the firing pulses theta , and the driving voltage across said AC circuit as indicated by the secondary winding of a voltage transformer (18), the voltage and current transformers being designed so that said two signals represent images to the same scale of the current of said circuit.
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