Functional behaviors of electric field grading composite materials

Non-linear resistive field grading materials (FGM) are used in different high voltage applications e.g. cable terminations, joints and rotating machines, where the electric stress is critical. It is already established that the use of FGM is an improved stress grading technique compared to conventional geometric methods. There is a constant endeavor within the electric power industries to extend these concepts to other power equipment. In order to achieve a wide spread use of FGM, they need to satisfy several functional requirements e.g. fire safety, tracking resistance, hydrophobicity, high thermal conductivity, besides certain dielectric properties e.g. field dependent conductivity, permittivity and low dielectric losses. In the present study ZnO filled silicon rubber (SiR) composite with different functional fillers, in total six different material compositions, are evaluated with respect to several important functional behaviors. Further, stress grading behavior of these six materials are demonstrated by finite element simulations on a generic electrode geometry and by performing inclined plane tracking test. Suitability of these material compositions to industrial applications are discussed.