Research On Partial Discharge Of Air Gap Defect In 110kV Basin Insulator

Gas Insulated Switchgears(GIS),as the important equipment of power system,has been widely used in urban power supply,high-voltage power transmission and transformation system.The basin insulator works as the core of GIS components.The GIS reliability of equipment operation are directly affected by the insulation performance.Some significant problems exposed in the process of operation and the actual production of the basin insulator were summarized in this thesis.In this paper,the air gap defect in 110 kV basin insulator were studied.Basing on the three dimensional finite element simulation analysis,the effect of different air-gap defects on the electric field distribution of basic insulators was studied.With the assistance of discharge test results,the effeciency of pulsed current method to the air-gap defects was verified,and the discharge development law was summarized.According to the actual product structure of 110 kV basin type insulator,the 3D structure model of basin-type insulator was established in this paper.In order to study the influence of air gap defect on the electric field strength of the basin insulator,the air gap model was established by simulating the air gap of the epoxy resin in the pouring process.The electric field distribution of basin insulator existing the air gap defects of different size and position was analyzed by using power frequency voltage.Due to the difference between expansion coefficient and contraction coefficient,there was a certain gap between the metal flange and the epoxy casting material after the basin type insulator was solidified and formed.Simulating of the actual product external air gap,the electric field distribution of basin insulator is analyzed respectively with different widths of air gap and different dielectric constants under power frequency voltage.In order to study the partial discharge characteristics of the air gap defects ofthe basin type insulator,the basin insulator partial discharge experiment platform was built in the study.Considering the basin insulator actual operation situation,the simulation of the high pressure basin insulator voltage grade and SF6 gas pressure environment.By designing the experiment scheme,the current pulse method was used to test the phenomena of partial discharge,before and after contrast.The reliability of the simulation results was verified,and the discharge rules of cracks in the insulator was summarized with the results of the experiments.In the processes of electrical performance test for a large number of basin insulators,we found that the phenomenon of instability under normal test conditions existed in the partial discharge tests of the basic insulator with metal flange.This study combined the three dimensional finite element simulation analysis with the verification test at the same time,which confirmed the main cause of the phenomenon due to the lower air gap width,which lead to partial discharge.By altering the proportion of filler parts to adjust the dielectric constant and the air gap width of the epoxy resin casting material,the electric field of air gap had been optimized,and the qualified rate of the product had been improved.