Comparison between the DC leakage currents of polymer housed metal oxide surge arresters in very humid ambient conditions and in water immersion tests

The behaviour of leakage currents of seven different types of commercially available polymer housed metal oxide surge arresters was studied in very humid ambient conditions during a 16 month test. During the test series many different combinations of mechanical, electrical and humidity stresses were applied to the test specimens in order to obtain the range of leakage current behaviour possible for the different arrester types in humid ambient conditions. The leakage current behaviours measured for the different arrester types are compared to their behaviour in the boiling water immersion test. This wide comparison gives valuable information of possible leakage current behaviours of several modern arrester types in humid ambient conditions and especially of the suitability of the boiling water immersion test for sealing testing of polymer housed arrester types. In general, both tests revealed the same kinds of DC leakage current behaviour in the different arrester types although some effects of different arrester structures and water penetration phenomena were observed.