Hydrophobicity characteristics of algae-fouled HVDC insulators in subtropical climates

Algae contamination was observed on the surface of composite insulators in a subtropical environment especially China; this contamination affects the external insulation performance of high voltage direct current transmission and distribution equipment. This paper explores the effects of algae on the hydrophobicity of silicone rubber under various circumstances and its mechanism, through hydrophobicity experiments and the measurements of surface conductivity and flashover voltage. Particularly, as a biological contaminate, algae population was changing during the test period, so the results were corrected to illuminate the effect of algae growth. Among the climate parameters, humidity was noted as the major environmental factor affecting the extent of the decrease of hydrophobicity rather than temperature and illumination. Other factors, such as algae density and surface roughness, played a minor role in the influence of hydrophobicity of algae-fouled insulators. The surface conductivity increased with algae cells density in different humidity exponentially. The algae contamination decreased the flashover voltage significantly with the change of algae density. Besides, extracellular polymeric substances, including polysaccharides and proteins, were deduced to be primarily responsible for the change of hydrophobicity because of their strong viscosity and water adhesion effect. The results about hydrophobicity of algae-fouled silicone rubber could provide useful information for the maintenance of algae-fouled insulators.