Analysis of the Influence of Ambient Temperature on the Optical Fiber characteristics of Fiber Optic Current Transformer Sensor

Fiber optic current transformer (FOCT) has become an important measuring equipment in Ultra-high voltage(UHV) converter station, because it has the advantages of large dynamic range, nonmagnetic saturation, digital and analog interface output. Previous studies mainly focused on the uniform temperature change of sensing optical fiber and optical fiber 1/4 wave plate, but under complex working conditions, the fiber optic current transformer is disturbed by the nonuniform temperature of the surrounding environment for a long time, and the characteristic analysis of sensing optical fiber at uniform temperature can not fully reflect the change of FOCT ratio error. Therefore, this paper uses the COMSOL finite element simulation software to model the part of the optical fiber leading from the lower side of the sensing fiber ring, and analyzes that the sensing optical fiber will produce nonuniform stress under the influence of nonuniform temperature, which will affect the FOCT measurement ratio error. When the current of the current-carrying conductor is 3000A, FOCT meets the error requirement of 0.2% in the environment temperature range of -80.0~7.9 °C, and the FOCT ratio error is not zero when the initial temperature is 25°C. That is to say, with the increase of wire current, the low temperature characteristic of FOCT ratio error will increase, while the high temperature characteristic will decrease.