Electrical properties of different composite materials for stress relief in HV cable accessories

In order to ensure optimal electrical performances of high voltage cable accessories an important aspect which determine both the steady-state long-term and impulse performances of the components, resides on the appropriate selection of the grading material. The use of a simple circuital approach, and significant control parameters, allow the evaluation of suitable limits for the values of the resistivity and permittivity of the adopted composite material which should guarantee a reliable operation of the components. In order to supply this significant information and compare the performances of thermosets and rubber based composites, typically adopted in these applications, the electrical properties of carbon black-loaded polyolefins and EPDM materials are analysed for a broad range of applied field and temperature.