The purpose of this study is an investigation upstream of polymer insulator ageing and rupture. We studied the electrical and physicochemical properties of a low-density polyethylene (LDPE) used in high-power insulated cables. Space charge measurements using pulsed electroacoustic method and thermally stimulated depolarization current (TSDC) were carried out on LDPE samples, with and without antioxidant, at different temperatures. TSDC peaks were observed only in the presence of an antioxidant. Furthermore, a TSDC anomalous peak was revealed for the sample containing an antioxidant and polarized at 50 degrees C. All the TSDC peaks are interpreted as trapped charges and can be explained by measuring the space charge distribution within the sample bulk. (C) 2008 Wiley Periodicals, Inc.