The missing link - The role of space charge in polymeric insulation lifetime

Polymeric insulation in power equipment experiences degradation and ageing under service conditions. The determination of remaining life plays a key part in the asset management. This requires an ageing indicator which can be used to monitor the status of the insulation. In this paper a simple model based on trap creation has been proposed and a concept of critical trap density can be used to describe the lifetime of the insulation. Assuming the power law relationship between the trap creation and the electric field, the empirical inverse power law can be derived. This allows one to relate the physical mechanisms and ageing processes (trap generation). Since the number of traps and energy depth of traps have direct influence on charge dynamics, using the two energy levels of trap depth model developed previously it is possible to estimate the trap density through changes in space charge dynamics. Further work is necessary to establish the direct relationship between trap density and the remaining life of the polymeric insulation.