Techniques for the estimation of ac space charge accumulation threshold for insulating materials

A new method for the detection of the ac electrical threshold for space charge injection in polymeric materials is presented in this paper. The ac charge injection-extraction dynamic in discussed, and experimental procedures are proposed to establish the electrical field for charge injection. These procedures are based on the observation of the space charge profiles obtained by the Pulsed Electroacoustic technique. The ac threshold data provided by the two tested materials i.e. LDPE and XLPE, are compared with dc threshold results, showing that the r.m.s. ac injection threshold values are very close to, but slightly smaller than, the dc ones.