Mechanism And Suppression Of Temperature Effect Of Sensor Head For Fiber Optic Current Transformer

Due to the advantages of high pressure resistance,no magnetic saturation,and high safety,the Fiber Optical Current Transformer(FOCT)is an ideal alternative product to traditional electromagnetic current transformers.After years of development,FOCT have become increasingly mature,especially in the background of China's vigorous development of a strong smart grid with Urtra High Voltage(UHV)power grids as the backbone grid,high-precision FOCT will be further developed.The FOCT is very sensitive to temperature diaturbances,especially the fiber ring is the part where affected by temperature most severe.Therefore,whether the influence of temperature disturbance can be handled well determines the measurement accuracy and stability of the FOCT.In order to improve the measurement accuracy and temperature stability of the FOCT,the paper focuses on the problem of the temperature disturbance of the fiber ring,studied the temperature error mechanism and the suppression method respectively.First,based on the theoretical basis of closed-loop control,Faraday magneto-optical effect,and Shupe thermal effect,a discretization mathematical model between the temperature output error of the FOCT system and the temperature change rate of the fiber ring is established by using the Jones matrix,and the effect of temperature disturbance on the measurement accuracy of each optical fiber and system in the fiber ring is analysised accurately by the finite element method,it is concluded that the temperature output error of the system decreases with the decrease of the temperature change rate of the optical fiber ring.Secondly,in order to control the temperature change rate of fiber ring,the paper designs a new type of optical fiber sensor head,the temperature change rate of the fiber ring without heat-off spool and the fiber ring with heat-off spool was compared and analysised,the system output error caused by the heating of the two fiber ring was also compared and analysised,and the effectiveness of the novel optical fiber sensor head in supressing the temperature error also was verified.Finally,in order to further-improve the temperature performance of the new fiber-optic sensor head,improving and optimizing the new fiber-optic transducing head.The temperature performance of the heat-off spool is analyzed by changing the heat-off spool structure,the spool size and the spool wall production material.In addition,due to the heat-off spool can homogenize the temperature field of the fiber ring,a space-symmetric double-column fiber ring can be used in place of the four-pole ring as a sensitive ring,and study the effect of the fiber wrapping method on the thermal performance of the system.The research results show that the improvement and optimization of the new type of optical fiber sensor head is of great significance for the improvement of the temperature performance of the system.The output error model of the FOCT system provides a new idea for solving the temperature disturbance problem.The design of the new fiber optic sensor head provides a new solution to the problem of temperature disturbance of the fiber ring,and the improvement and optimization of the new sensor head further improve its Engineering practicality.The results of the project have the potential market economic value which could effectively solve the temperature disturbance problem which restrict the development of FOCT.