A contribution to unravel the mysteries of electrical aging under DC electrical stress: where we are and where we would need to go

Discussions and proposals about the way damage grows in insulating polymers under DC electrical stress are the core of this paper. It is shown that there are reasonable indications that DC electrical aging has features in common with mechanical aging under static stress, being local, rather than global, plastic deformation the major phenomenon associated with electrical aging. Formation of cavities, or crazes, of size large enough to trigger highly energetic phenomena bringing insulation to failure completes the picture. Regarding the growth of damage from cavities, modeling of partial discharge, PD, is presented, based on the physics of discharge in condensed matter, thus in a fashion that Eric Forster would have liked. While PD inception is satisfactorily described and life estimations seem to provide reasonable results, a lot more work has to be carried out to take into account the modification with time of defect property chracteristics, which can even cause periodic stop of PD in low-density region of an insulating material. On the whole, this paper provides indications of feasible footpaths towards understanding why insulating polymers fail under DC stress, in which way their endurance could be improved and the design stress could be raised, but there is not any final and steady answer yet to the complex problem of insulation electrical aging.