4 - Development of the laser current transformer for the extra-high-voltage power transmission lines

Further developments and experiments of the laser current transformer for extra-high-voltage power transmission lines are described. A developmental model for reproduction of a large current waveform of extra-high-voltage is constructed by using a 6328-Å gas laser beam and a flint glass rod fixed on the top of 30-cm-diameter supporting insulators. It was tested at the Shiobara Laboratory of the Central Research Institute of the Electric Power Industry. Experiments under large current and/or high-voltage conditions of a 50-Hz continuous and impulse current basis reveal that the transformer will perform its functions satisfactorily in an extra-high-voltage line. A microwave current transformer (under development in Japan), which uses a Faraday rotation of a microwave instead of a laser beam for measuring a current of an extra-high-voltage wire, is compared with the laser current transformer.