2 Low-cost robust Electrooptic hybrid current sensors capable of operation at extremely high-potential

Two very simple electro-optic hybrid schemes which convert the output from a conventional current transformer to an optical signal are presented. These systems may be used to indicate the presence of and/or measure the magnitude of large currents at very high potential. The first scheme would be very useful for indicating whether the conductor was carrying current or for making measurements within an accuracy of approximately 10% at extremely high potentials. Whilst the second scheme, with a demonstrated minimum detectable signal of 0.32 A/square-root Hz, provides a simple and low-cost way for accurate current measurement in high potential locations. The optical signals from the measurement scheme can be transferred for subsequent demodulation via multimode fibers hence greatly reducing the electrical insulation required for safe operation of the current transformer thereby offering a significant cost saving in its manufacture.