Dielectric behaviours of cross-linked polyethylene (XLPE) impregnation with compressed SF6

Through comparative tests, the problem of vacuum-impregnation for a length of cable could be overcome by initial granular polyethylene being vacuum-impregnated and cable conductor being filled by compressed SF₆ after manufacture. For this purpose, the affects of pressure, temperature, voltage wave form and simulation of production process on the breakdown strength and electrical treeing characteristics of XLPE or PE samples impregnated with SF have studied intensively. The influence of thermal ageing on mechanical strength of the above samples are also investigated in this paper. Finally, on the basis of measured data, the distribution of SF₆ concentration, temperature and dielectric strength along the radius in insulation of XLPE cables are calculated