Abstract: The invention is based on an electrical current measuring device for measuring at least one alternating current, with at least one inductive coupling unit, which is intended to convert at least one electrical primary signal into at least one electrical secondary signal, and with a computing unit, which is intended to determine the primary signal from the secondary signal. The computing unit is intended to take into account at least one higher harmonic of the secondary signal when determining the primary signal.

Abstract: The invention is based on an electrical current measuring device for measuring at least one alternating current, with at least one inductive coupling unit, which is intended to convert at least one electrical primary signal into at least one electrical secondary signal, and with a computing unit, which is intended to determine the primary signal from the secondary signal. The computing unit is intended to take into account at least one higher harmonic of the secondary signal when determining the primary signal.

Abstract: So that internal faults (7) on high-voltage lines (4), generators (5), transformers (6) and other objects to be protected are more reliably detected even with saturated current transformers (3,8) and a tripping of protective measures such as, for example, an opening of switches (2,9) is reliably prevented in the case of external faults and short circuits (10), alternating current measurement signals (I.sub.1 ',I.sub.2 '), which are proportional to the alternating currents (I.sub.1, I.sub.2) flowing into the object to be protected, are detected by means of the current transformers (3,8). The alternating current measurement signals are then supplied via a low-pass filter (12), a transformer (13), a channel selection device (14), an analog/digital converter (15) to a microcomputer (16) for analysis. In the case of a fault, the microcomputer (16) provides a protective tripping signal (F=1) to switches (2,9) which open and thus isolate the object to be protected (4-6) from high-voltage lines (1,11).