Influences of aggregative state on electrical trees growth characteristics under cryogenic condition
The electrical trees aging processes in different kinds of polymer directly determine the insulation property; therefore the aggregative state in polymer insulation under cryogenic condition is specially focused in this paper. The results indicate that polymer brittleness plays an important role for electrical ageing under cryogenic condition as well as the mechanical destruction which is induced by PD. Thus the influence of aggregative state on aging processes is less obvious under cryogenic than that at room temperature. The crystallinity and average size of crystallite can both be decreased with the increase of cooling-down speed. The trees morphological properties imply that trees grow directly to the crystal regions under cryogenic condition and large branch with big space intervals can be formed with small size of crystals, which are also proofed in the samples after many times hot and cold circles treating.