Abstract
This study investigates and compares two different silicone anti-failure rejuvenation fluids based on alumina nanofiller in terms of their capability in rehabilitation and restoration of water tree aged medium voltage cross-linked polyethylene (XLPE) distribution power cable insulations. These two rejuvenation fluids include two types of silane coupling agents used for forming chemical bonds between nanoparticles and cable polymer matrix, filling water tree micro voids and drying the humidity of cable insulation. These two compositions contain γ-alumina nanoparticles which have applications in improving dielectric properties, treating and modifying the surface of the aged insulation and filling water tree micro voids. After injecting the two rejuvenation fluids in two groups of aged cables, dielectric loss factor (tanδ) of the injected samples was measured every week from day 1 to 30 and their results were compared with the new unused and aged samples. Microstructure analysis of the aged and rejuvenated insulations was carried out by scanning electron microscope (SEM) and the chemical bonds of the aged and rejuvenated samples were detected and monitored by Fourier transform infrared (FTIR) spectroscopy. The type of elements and the weight percent of the absorbed elements on the surface of rejuvenated insulations were studied by energy disperse X-ray spectroscopy (EDX). After one month from the injection, it was revealed that tanδ of the injected samples (both rejuvenation fluids) decreased in a way that their tanδ values were even less than the new unused samples. Results of SEM analysis illustrated that rejuvenation fluids filled the water tree micro voids and modified the insulation surfaces. FTIR analysis also indicated that both silicone fluids penetrated in cable insulations and the peaks related to silicone and alumina bonds could be clearly observed. EDX test demonstrated and compared the amount and weight percentage of the rejuvenated elements such as silicone, aluminum and iron. Finally, through the results of these 4 tests, the best rejuvenation composition was selected among these two compositions