Investigation of the effect of roughness value on the wettability behavior under electric field in XLPE materials used in medium and high voltage applications

Abstract

XLPE material, which is widely used as a polymeric insulator in medium and high voltage applications, plays an active and important role in electricity transmission and distribution. The aging of XLPE materials due to various factors is inevitable. It is observed that fault and troubleshooting increase with the aging of materials. Wettability behavior is one of the fundamental surface properties of materials. Surface properties also play an important role in the determination and estimation of the service life of the materials. By performing contact angle measurements for XLPE material surfaces, determinations and evaluations about the wettability behavior (hydrophobicity and hydrophilicity) of the materials can be made. In this study, contact angle measurements of XLPE materials with different roughness values were carried out under the electric field. With the help of the experimental setup designed and implemented, XLPE samples were placed between the aluminum plane electrodes and exposed to the electric field. 10 kV HVDC high-voltage generator was used when performing the measurements. 1.8 M (molarity) saltwater in the volume of 20 µl was dropped on the XLPE sample surface with a syringe and the droplet snapshots were taken with a digital microscope for contact angle measurement under the electric field. The acquired images were processed using basic image processing techniques with the help of a GUI developed on the MATLAB software platform. Contact angle values were obtained for 50 XLPE-A (Ra = 0.469 µm) and 50 XLPE-B (Ra = 5.456 µm) sample surfaces. Contact angles obtained from rough XLPE surfaces under the electric field allow for evaluation of the service life of XLPE materials. While determining and evaluating the wettability behavior of XLPE materials, an approach based on the contact angle is presented. As a result, the correlation between the electric field, surface roughness, wettability, and contact angle was observed. When the results were evaluated, it was observed that the contact angle values close to the hydrophobic surface value approached the hydrophilic values as a result of the increase in surface roughness and/or exposure to the electric field. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.