Electrical Response of Inclined Composite Insulator Surfaces to Discrete Water Droplets

Droplets on composite insulator surfaces can change surface conductivity and affect leakage current. In this study, an Adjustable Inclined Plane Test system (AIPT) was developed to examine the effect of inclination on the electrical behaviour of a composite insulator with a controlled discrete water droplet. Tests were performed at inclination angles from 0° to 90°, 15-step increment, for 3 h. Leakage current was recorded continuously, while contact angle and hydrophobicity were measured before and after the test. Scanning Electron Microscopy (SEM) analysis was used to examine the surface after testing. Higher mean leakage current was observed at 0°, 15°, and 30° than at 45°, 60°, and 75°. At the lower inclination angles, droplets remained on the surface before evaporating, whereas at the higher angles, droplets tended to elongate and move downward under gravity. The contact angle and hydrophobicity results also indicated greater surface changes at the lower inclination angles. SEM images showed higher levels of surface change at lower angles and less change at higher angles. At 90°, the droplet did not remain on the insulator surface, so the sample stayed dry and showed a relatively smooth surface. These results show that inclination affects water retention, leakage current, and surface condition. The AIPT can be used for controlled evaluation of composite insulator performance under different water and inclination conditions.