Electrical properties of field grading materials influenced by the silicon carbide grain size

Non-linear field-grading materials are used to avoid stress concentrations in many AC and DC high voltage applications. One way to obtain materials having the desired non-linear characteristics is to use compounds, such as an insulating polymer with a semiconducting filler. A possible filler is silicon carbide (SiC). In this study ethylene-propylene rubber (EPDM) mixtures containing a wide range of SiC particle sizes, from approximately 0.7 to 23 /spl mu/m, have been used to evaluate variations in resistivity, permittivity and nonlinearity. The material properties have been electrically characterized and analyzed both at low voltage in frequency domain and at high voltage in time domain.