Chemical defects and electron trapping relevant to cable dielectrics

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 industrial electrical cables is computed. The trap depth is obtained using quantum mechanical 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.