663 / 2022-03-31 11:11:19

Simulation study on abnormal discharge in insulator of optical fiber current transformer

optical CT,,internal discharge,UHVDC,fault analysis,Finite element simulation

Purpose/Aim

Pure optical current transformer is widely used in current monitoring of valve hall and DC field in UHV DC converter station. With the progress of technology and rapid development of materials, new pure optical fiber transformers filled with light weight gels are applied in UHV multi terminal flexible DC projects. Its insulation reliability significantly affects the safe and stable operation of the system. However, during the application, it was found that abnormal discharge occurred in the shielding area of hardware, as shown in figure 1. Therefore, it is necessary to explore the causes of abnormal discharge and put forward requirements for the improvement of the insulator used for optical current transformer.

Experimental/Modeling methods

In order to analyze the cause of insulation discharge in the shielding area of fittings, the finite element simulation calculation model of photocurrent transformer is established The material parameters inside the photocurrent transformer are obtained through the test. The electric field distribution characteristics in the optical fiber transformer are obtained by calculation, and the variation law of the maximum electric field intensity in the insulator with the material characteristics is studied. According to the analysis results, suggestions on the matching and optimization of optical fiber sheath materials are put forward

Results/Conclusions

The simulation results show that due to the low resistivity of the protective layer material of optical fiber insulator, the potential is introduced into the shielding area inside the fitting, resulting in the concentration of local electric field. Adjusting the matching of insulating materials for optical fiber sheath to the insulation system can improve the distortion of local electric field and avoid abnormal discharge The research results of this paper can provide reference for the design of similar insulation systems.