Abstract
Authors are developing a system that measures the differential optical intensity from two flint glass fiber type current transducers (OCT) directly connected in a series by an optical fiber and performs differential current measurement. In this paper, we propose adding a summed current information to the subtracted current information as input information of a relay unit. We designed an experimental model including the relay unit applicable to the under ground power line of 20km, 66kV. Evaluation by numerical analysis and examination was performed. In the large current test this model did not misjudge. The total error of OCT is about ±3%, because its own error ratio is ±1.5% combined with its temperature dependence of ±1.5%. However we confirmed that the error is not a problem in operation of this system. We found that the influence of vibration, shock and bending of the optical fiber for transmission can be reduced by using a depolarizer. It has been checked that the proposed system can satisfactorily operate under the conditions we assumed on practical use.
