Lifetime dependence on relative humidity of polymers subjected to PD aging

The work presented in this paper consists of a systematic study on the influence of moisture on the behaviour of polymers submitted to Partial Discharges. Three chemically different polymers have been submitted to PD until breakdown, varying the relative humidity from 17% to 83%. Qualitatively the same evolution of the samples' lifetime with moisture is found for the three of them. Lifetime increases with increasing humidity up to a critical value; further increase in moisture involves quick diminishing of lifetime. This value seems to depend on the ability to absorb water of each of the polymers.