DC resistivity and AC breakdown strength of flexible polypropylene (trade marked name Hifax) cable insulation materials have been measured at selected temperatures. The AC breakdown data has been analysed in terms of Weibull distribution. The results show that Hifax cable insulation has a higher AC breakdown strength than EPR (ethylene propylene rubber) and XLPE (crosslinked polyethylene), both of which are widely used for DC cable insulation. It is concluded that blending Hifax with ordinary polypropylene decreases the breakdown strength. The DC resistivity of Hifax is larger than that of XLPE and oil-impregnated paper insulations. It has been found that the electrical stress coefficient of resistivity of Hifax cable insulation increases with temperature, which may have important engineering implications. An anomalous drop in resistivity has been observed for Hifax at high electrical fields, suggesting charge trapping and detrapping processes are present in these cable insulations. (c) 2006 Springer Science + Business Media, Inc.