1. General

1.1 Common features of material breakdown

Several features of breakdown are common to all dielectric materials:

• the breakdown is localized: it affects only a tiny area of the medium, with the healthy part often retaining its original properties (even after a long period under tension);

• electronic processes are always involved in the initial phase; breakdown can result from the cooperative effect of a very wide variety of phenomena (thermal, mechanical, electrohydrodynamic, chemical, etc.) that are more or less inter-correlated, giving rise to a streamer , a more or less luminous, branched and conductive tree that precedes the arc ;

• the effects of scale are considerable:...