Patent ID: 6828770
Filing Date: 2004-12-07
Classification: G01R

Abstract:
A method for measuring at least one characteristic parameter of an alternating current in a conductor, the parameter of the alternating current comprising at least one of a group of waveform characteristics of the alternating current; phase of the alternating current; harmonic content of the alternating current; and a derivative of the alternating current, the method comprising the steps of:measuring a magnetic field around the conductor at a point along the conductor to obtain a measured magnetic field value; integrating the measured magnetic field value to thereby derive an analogue voltage signal representative of the magnetic field; adding a direct current (DC) offset signal to an alternating current (AC) component of the magnetic field; amplifying the analogue voltage signal; converting the amplified voltage signal into a digital voltage signal, the digital voltage signal being within a dynamic range of signal values; measuring the digital voltage signal including a DC component in the digital voltage signal, and when the amplitude of digital voltage signal reaches a predetermined value, adjusting a gain setting of the amplification to vary the dynamic range of signal values, and varying the DC offset signal in response to the measured DC component in the digital voltage signal; generating an output signal representative of the parameter of the alternating current based on the amplified voltage signal and the gain setting; and deriving a second analogue voltage signal representative of the measured electric field in the vicinity of the conductor; whereby in measuring the variance in the magnitude of the electric field generated by the conductor in conjunction with variance in the conductor, faults in the conductor may be detected.