For this test, clean water was vaporized on internal columns of arresters to simulate the presence of humidity in the interior of the equipment. Analyzing the thermal images and the temperature patterns it is possible to notice that different effects were obtained for each tested arrester. Anyway, in both cases, a large increase of temperature was visible in distinct regions of the arrester. These regions had suffered this increase from temperature probably due to circulation of vapor and to the occurrence of internal discharges, as explained previously.