Optical sensors for electric substations: a voltage presence detector using a liquid crystal cell

A new fiber optic voltage presence detector is presented, based on the detection of the excitation state of a liquid crystal cell by means of an optical technique. The sensor was designed to work in electric metal-clad medium-voltage (MV) switchboards with SF/sub 6/ insulation where EM immunity and insulation requirements make fiber optic sensing the most suitable choice. The small size of the probe, its high reliability, and its low cost make it especially suited for these compact structures. Working principle and design details are reported.<
>