8C1 - The laser current transformer for EHV power transmission lines

A current measuring device applicable to an extra-high voltage power transmission line higher than 500 kV is proposed with preliminary experimental results. It obtains the instantaneous magnetic field ajacent to a transmission wire by measuring the angle of Faraday rotation of a laser beam in a flint glass rod. The laser beam is transmitted and analyzed at a ground potential site, and in the energized part this device has neither insulated conductors nor active elements. An experimental laser current transformer yielded a sensitivity of 66 mV per 100 A and good linearity. Various sources of error and modifications are discussed.