Abstract: The present invention provides a method of determining a current in a conductor. The method comprises the steps of determining the nth spatial derivative of at least one vector component of the magnetic field associated with the current at at least one position and calculating the current from the nth spatial derivative. The present invention also provides an apparatus for determining a current in a conductor. The apparatus comprises a means for determining at least one vector component of the magnetic field associated with the current at at least two different positions and a means for determining the nth spatial derivative of at least one vector component of the magnetic field from the or each vector component of the magnetic field measured at the at least two positions. The apparatus also comprises a means for calculating the current from the nth spatial derivative.

Abstract: A method for measuring at least one characteristic parameter of an alternating current in a conductor, the method including the steps of measuring the magnetic field around the conductor at a point along the conductor; deriving an analogue voltage signal representative of the measured magnetic field; amplifying the analogue voltage signal; converting the amplified voltage signal into a digital voltage signal; measuring the digital voltage signal and, when the amplitude of digital voltage signal reaches a predetermined value, adjusting a gain setting of the amplification; and generating an output signal representative of the parameter of the alternating current based on the amplified voltage signal and the gain setting.

Abstract: A method of detecting for a fault on one of a plurality of adjacent, alternating current carrying conductors; the method comprising the steps of detecting the waveform of a first component of a magnetic field vector representative of the magnetic field around the plurality of conductors at a location along the conductors; detecting the waveform of a second component of the magnetic field vector; monitoring, at the location, the two waveforms for any change in the waveforms; and detecting for a fault on one of the plurality of the conductors as indicated by a change in either one or both of the waveforms.