Importance

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Abstract

A current sensor for measuring a time-varying electrical current (I.sub.m) in a portion of primary conductor (1), the sensor including a sensor conductor comprising first and second ends (3,4) for connection to a signal processing circuit, a first conductor portion extending from the first end and having a plurality of windings (5) to form a first coil portion, and a second conductor portion returning to the second end. Centres of the windings define a median coil place substantially parallel to the magnetic field (H.sub.m) generated by the time-varying current (I.sub.m) to be measured, the sensor conductor defining one or a plurality of interference field surfaces as seen projected on a plane parallel to the median plane enclosed by clockwise or anti-clockwise interference field current circulating portions (22,23) of the sensor conductor. The second conductor portion is arranged such that the surface area of the one or more projected interference field surfaces is close to zero or less than ten times the measurement surface area (A.sub.m) of a winding, and/or such that the voltage induced by a magnetic interference field component (H.sub.s) orthogonal to the median plane in the clockwise interference field circulating portions is substantially cancelled by the voltage induced in the anti-clockwise interference field circulating portions.

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First Claim