On the monitoring of the degradation of outdoor organic insulation

Degradation phenomena which occur in correspondence with some interfaces which are present in organic composite insulation for outdoor high voltage applications are discussed. In particular, on the basis of the data obtained from either accelerated or environmental aging tests carried out on cycloaliphatic epoxies, results are presented regarding the effect of the applied electric field on the surface degradation of samples and the differences in the dielectric behavior due to sorbed water in filled vs. pure epoxies. The results obtained demonstrate that the presence of the inorganic phase in filled epoxies modifies the dielectric response of water-conditioned materials compared to that of the pure resin. Moreover, higher values of the electric field on the surface produce increased localized material alterations, which in turn cause the lowering of relevant electrical parameters such as the surface resistivity