Insight into the new role of titanium isopropoxide catalyst on rejuvenation for water tree aged cables

In this paper, a new role of titanium isopropoxide (TIPT) catalyst is revealed on rejuvenation of water tree aged cables, and TiO2 inorganic particles are found in the water tree voids after injecting a rejuvenation fluid. Through analyzing the products of TIPT hydrolysis, the nano-scale TiO2 particles are observed. This proves that the hydrolysis reaction of TIPT can generate the TiO2 particles. Furthermore, a water tree accelerated aging system with a needle electrode is used to obtain water tree in cross-linked polyethylene (XLPE) cable samples. The water tree aged samples are injected with a fluid including a siloxane and TIPT for rejuvenation, and the breakdown voltage of the injected samples is significantly higher than that of the water tree aged samples. By use of a scanning electron microscope (SEM) and energy disperse spectroscopy (EDS), some agglomerated TiO2 particles are found in the water tree areas of the injected samples. Also, the TiO2 particles are observed inside the breakdown channels of the injected samples. This indicates the TIPT can react with water in water tree and form the TiO2 gel to fill water tree voids. Because of the filling effect of inorganic TiO2 particles, the breakdown strength of the rejuvenated cables can be improved, which possibly suppresses the damage generated by the partial discharge inside the water tree.