Edge effect and its influence on the adjacent cavities in a composite insulator

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Salakjit Nilboworn
Kuntapon Mahamad
Weerachai Sangchay
Paisan Kongrueang


In high voltage measurement systems, fringing field effect is related to the degradation mechanism in insulators. The densely field stress can lead to insulator failure faster and cause further deterioration. Another reason for the localized degradation is the existence of a defect in the insulator. Therefore, the fringing field at edge electrodes and the field stress around the cavities, which are adjacent near the electrode, are important factors when investigating the degradation. This work showed the effect of the fringing field on a composite insulator specimen. Moreover, the 2D model was built in the COMSOL multiphysics program based on the experimental insulation test. The effect of cavity shapes were also conditions in the modeling. The experiment was performed using operation voltage 20 kV according to ASTM D149. The test structure consisted of two brass electrodes with a radius of 37.5 mm as a parallel plate with the composite insulator in between. Then, the failure possibility at the edge electrode from two methods were compared. The results revealed that the edge electric field was higher than in other areas. This field stress accelerated the pre-discharge within the cavities, significantly increasing the electric field intensity.

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