BREAKDOWN OF SOLID INSULATING MATERIALS

In solid dielectrics, highly purified and free of imperfections, the breakdown strength is high, of the order of 10 MV/cm.

The highest breakdown strength obtained under carefully controlled conditions is known as the "intrinsic strength" of the dielectric. Dielectrics usually fail at stresses well below the intrinsic strength due usually to one of the following causes.

(a) Electro-mechanical breakdown.
(b) Breakdown due to internal discharges.
(c) Surface breakdown (tracking and erosion).
(d) Thermal breakdown.
(e) Electro chemical breakdown.
(f) Chemical deterioration.