No flashovers were recorded during insulators’ tests.
Water droplets and dried zones of surfaces with declined
(degraded) hydrophobicity caused partial discharges and
dry band arching on the composite insulators but the intensity
and extent of dry band arching was low. The intensity of
partial discharges was higher on naturally contaminated
ISOELECTRIC composite insulators than on naturally
contaminated LAPP insulators. It may be related to the fact
that hydrophobicity of LAPP insulators is preserved better
and that certain degree of wetted contaminations’ diffusion
through the protective polymer layer takes longer than ca.
20 minutes that was the time period of a test.