Dielectric testing of solid insulation with respect to insulation coordination of low-voltage equipment

In real insulation systems with solid insulation, partial discharges usually occur far below the breakdown voltage. In the long run, these lead to the destruction of nearly all solid insulating materials. The question, How much time has passed until the partial discharges have destroyed the solid insulation?, is of little relevance in low-voltage equipment since the occurrence of partial discharge during normal use will, in general not allow a sufficient lifetime. Moreover, the results of such lifetime investigations are influenced by many parameters; therefore, statements with general validity cannot be made.