Interrogation of a conventional current transformer by a fiber-optic interferometer

A new approach to the measurement of large currents at high potential is presented in which the output signal from a conventional current transformer is measured by transducing the voltage developed across the transformer secondary into phase modulation in a fiber-optic interferometer through a piezoelectric element. The demonstrated current range was 140 A, although the system is capable of measuring current as great as 3000 A. The current resolution is >10−1A/Hz over a frequency range of 30–104 Hz.