Diagnostics of non-ceramic insulators with inhomogeneous field arrangement and wetting with different liquids

Non-ceramic insulators have been operated successfully during the past decades; however, the field experience with operating them beyond the originally planned lifetime is limited. To overcome the uncertainty of operation, it is necessary to implement a range of diagnostic methods covering the most critical degradation processes. There are several methods that have been used with success; still, there are degradation processes that may stay hidden in the case of on-site diagnostics. In this article, two experimental methods are presented. The first is the application of external electrodes around the insulator and measuring the inception voltage of discharges. The second process is similar to the standard hydrophobicity test and wet insulator test, but the wetting of the surface is performed with saltwater.