Study On The Relationship Between Surface Discharge And Decomposition Gas Of Bonded Insulator With SF₆ Current Transformer

Partial discharge of the basin insulator in SF6 gas current transformer will degrade the insulation performance of SF6 gas,resulting in breakdown of the basin insulator and equipment failure.In this paper,the relationship between the surface partial discharge of basin insulators and decomposition product of SF6 gas were studied to evaluate the operation condition of basin insulators through the change of decomposition gas content.The main contents include the following aspects:（1）The four types of metal defects existing on the surface of the basin insulator are simulated and compared,and the longitudinal concave metal defects are selected to fit the defects on the surface of the insulator.Through the simulation results and the actual fault analysis,the SF6 breakdown field strength can be reached when the applied voltage reaches 40 kV.（2）The insulator surface discharge and decomposition gas test platform are designed and manufactured,including the design and debugging process of the test chamber,the selection process of the basin insulator,pure SF6,standard gas and measuring equipments.The test platform can meet the experiment under different gas environments such as vacuum and SF6,and at the same time,it can extract air for component analysis.（3）The variation and correlation of partial discharge capacity,dielectric loss factor,SF6 decomposition gas under the condition of surface partial discharge are studied.The results show that the partial discharge parameters（Qiec and Qsum）,dielectric loss factor and the contents of SOF2,SO2F2 and CF4 of three SF6 decomposition gases increase with the increase of discharge voltage and time.The CF4 gas content increases steadily before breakdown,and its content increases significantly after each breakdown.The content of SO2F2 and SOF2 increases greatly in the initial stage of discharge,and then the increase rate of the two gases gradually decreases.（4）The correlation analysis of QIEC,Qsum and gas content shows that there is a significant positive correlation between them.Through the correlation index R2 analysis of the fitting curve,it is found that the fitting curve of Qsum infrared absorption peak height has the highest fitting degree with the test results,which can reflect the relationship between the discharge of pot insulator and gas content.This conclusion proves that the content of CF4 gas can be used to evaluate the partial discharge,aging degree and operation condition of the basin insulator of SF6 current transformer.