Selection of Optimal Outdoor Insulation for Refurbishment of 400 kV Substation Under Coastal Pollution by Milan Radosavljevic

Substations and overhead lines located near coastal areas can be affected by high levels of maritime pollution. For example, two particularly exposed Swedish substations, constructed in 1970s, are equipped with relatively short porcelain insulators – the only option available at time of construction. As such, there soon evolved the need to provide better pollution performance such that installation of live line washing equipment became mandatory. When it was recently decided to refurbish these substations, engineers wanted to forego this type of expensive washing system that was not operating fail-free – sometimes activating washing more often than needed while other times activating it too late. Also, there were cases where the washing system actually initiated flashovers instead of preventing them. This presentation describes the historical background and why the decision was made to select RTV-coatings for such applications in spite of the fact that the technical policy in Sweden is now to use superior pollution performing composite insulated apparatus at all new substations and also for refurbishment of existing substations. Moreover, a non-standard matrix of tests intended to help identify the optimal RTV-coating material is presented together with test results.