Evaluation of the hydrophobic property of composite insulators using Dynamic Drop Test

Long term reliability is one of the most important performance measures for high voltage insulators in the power transmission and distribution networks. To evaluate the longterm performance of insulators, properties such as hydrophobicity, surface roughness, and chemical composition are often studied. In this paper, evaluation of hydrophobicity based on the Dynamic Dropping Test (DDT) method is proposed. Using a high-speed camera (Vision Research Phantom v1610) with 65mm f/4.5 Macro-Nikkor lens and Nikon PB-6 bellows unit, which is fixed in a level 45° to the specimen surface, the full sequence of the water droplet making contact with the composite surface was recorded and analyzed. The DDT was performed on specimens of different ageing levels. Further investigation on hydrophobicity using the optical contact angle device (OCAH200) is performed to study the relationship between DDT over the surface and the contact angle. Our results show that more time is needed for the water droplet to settle over the surface when the hydrophobicity is decreased due to aging. Scanning Electron Microscopy (SEM) images showing the level of degradation on the surface of the specimens are included. The results obtained in this work indicate that the DDT method is sensitive to the hydrophobic properties, which can be applied as a new method for hydrophobicity evaluation of polymeric insulators.