On the effect of anisotropy in nonlinear composite materials for stress grading applications-a numerical study

The production technology of carbon-black loaded polyolefins adopted for stress grading purposes in ac cable terminations may impart, in addition to the nonlinear electrical properties, an anisotropic behavior to the material. In this paper a numerical study is presented in order to study the influence of both anisotropy and nonlinearity on the electrical field dynamics inside cable terminations adopting stress grading carbon-black loaded composites. The nonlinear anisotropic conductivity is properly taken into account in the model, allowing a sound understanding of the influence of such property on the stress grading performances of the considered accessory. The numerical results for sinusoidal power frequency and standard impulse voltages demonstrate the role of the different conduction mechanisms on stress grading efficiency and give useful indications for an effective material characterization.