Elemental strain and trapped space charge in thermoelectrical aging of insulating materials. Life modeling

On the basis of the new concept of elemental strain, used to describe a possible aging process occurring in polymeric materials, the expression for the life model, already proposed in previous paper, must be modified, taking into account the possibility that the local strain is an elemental property of the polymer morphology, as suggested by molecular quantum calculations. By doing so, a connection can be established between the life model and space charge densities as revealed by experiments. The derivation of this new model and the correlation with analytical measurements is the subject of this paper. Applying this connection to electrical aging and space charge data for the same crosslinked polyethylene (XLPE) material has resulted in a set of material factors that we have demonstrated are both consistent with experiments and also produce physically feasible space charge fields that are capable of driving the proposed aging mechanism to the extent required.