Electrooptic methods for measurement of small DC currents at high voltage level

Two electrooptic methods for measurement of DC currents at high voltage levels, extending from the nanoampere range and up to the milliampere range have been developed. By switching the polarity of a measured DC voltage across a Pockels cell, DC currents can be measured and transmitted along an optical fiber to an electrooptic converter. Using an electronic circuit, the measured signal can be converted into a modulated-frequency form for transmission along an optical fiber. These systems are described, measurement results are presented and improvements to be made in the future are outlined. The measurement methods can be used for both development and supervision of electrical insulating systems