The interrogation of a conventional current transformer using an in-fibre Bragg grating

An alternative approach for measuring large currents at high potentials is presented. The output signal from a conventional current transformer is measured by transducing the voltage developed across the transformer secondary into a shift in the reflected wavelength from an in-fibre Bragg grating using a piezoelectric element. A pseudo-heterodyne detection scheme was used to determine this shift. We demonstrate the scheme's performance over a current range of 700 A. The current resolution was about 1.5 A HZ(-1/2) over a frequency range of about 50 to 5 x 10(3) Hz.