Electrical characteristics of insulating materials

The aim of this article is to enable the pre-selection of a solid insulator, based on the most commonly used electrical characteristics:

• tangent of the loss angle tan δ ;

• relative permittivity ε _r ;

• dielectric strength ;

• surface resistivity ;

• transverse resistivity ;

• resistance to high-voltage (HV) spark current;

• path resistance index.

Readers should not forget to check that the material chosen is compatible with the mechanical and thermal stresses envisaged. This not inconsiderable aspect of the problem of choice, as well as questions of price and ease of installation, are not dealt with in this article.

The measurement methods, values and significance of the characteristics of solid insulating materials are given in article D 2 310 of the Electrical Engineering textbook.