Chemical defects and electron trapping relevant to cable dielectrics

Abstract

chemical defects and impurities are thought to be responsible for the deep trapping of charge carriers in polymeric insulating materials such as peroxide crosslinked polyethylene (XLPE). Such excess charges, referred to as space charges, might cause localised high electric stress, possibly leading to dielectric breakdown under DC voltage application. Chemical defects and impurities found in electrical cables are inherent to the different compounds designed for the crosslinking process technology. In this study, the trap energy of a range of chemical species relevant to indwial electrical cables is computed. The trap depth is obtained using quantum mecbanical tools, namely the Density Functional Theory (DFT). The DFT is employed to compute the electron affinity of the compounds. Then, a relation between electron affinity and trap depth is employed. Calculations have been performed for isolated molecules as well as including the effect of a polymeric environment.

Study and analysis of conduction mechanisms and space charge accumulation phenomena under high applied DC electric field in XLPE for HVDC cable application

“…Space charges can be trapped in the polymer. From a chemical point of view, the peroxide decomposition products facilitate the trap presence [14], [15] and heterocharges [16]. In our study, this assumption cannot be verified through space charge measurements because the samples have been degassed before measurement and the high poling temperatures used (above 70°C) could favor the degassing of the possible remaining species.…”