A probabilistic design method for polymeric structures to operate at high electrical stress

Fluid filled cables continue to display reliable operation at high design stresses: conductor screen stresses for paper and PPL designs are 15 kV/mm and 18 kV/mm respectively. Polymeric cables, and accessories, have not been in service long enough to establish, empirically, a limiting value for the design stress as used for fluid filled designs. Consequently mathematical models are necessary to calculate the relationship between design stress and service life. The development and the use of these mathematical models for service applications are described in this paper.