Contribution on the Specification of an Aging Test for the Insulation of Enclosed, Air-Insulated Switchgear

Because of high humidity and condensation, layers of moisture are formed on the surface of insulating materials in indoor switchgear installations which, as a result of contamination, are conductive electrolytic boundary layers. When this happens, electrochemical interactions can produce aging of the insulating material surfaces that may even lead to failure of the insulation. Basic investigations were carried out on a rod-shaped model insulator with simul taneous subjection to an electric field, moisture, and polution. Electrical, chemical, and optical diagnostic methods make it possible to determine aging related surface changes. Based on these results and taking into account the results of work done by the International Working Group IEC-SC17/WGIO "Aging Tests", proposals are discussed for an aging test for enclosed indoor switchgear. In particular, procedures are discussed for simulating the aging phenomena with time compression. The suitability or nonsuitability of individual parameters are discussed.