Behaviour of the DC leakage currents of polymeric metal oxide surge arresters in water penetration tests

The behaviour of seven commercially available polymer-housed metal oxide surge arrester types was studied in +70/spl deg/C and boiling water immersion tests. The DC leakage current of the arresters was used to diagnose the humidity penetration inside an arrester. The recovery features after an immersion test for different arrester types were measured and discussed. Together with the immersion and recovery tests, a humidity penetration test in very humid air was performed. For the first time, the behaviour of different arrester types in immersion tests was compared to their behaviour in a humidity penetration test with realistic ambient conditions. The resistance to moisture penetration varied greatly in the arrester types tested. Also, recovery of the DC leakage current varied between the arrester types depending on their structure. The results from the tests in very humid air indicate similar arrester behaviour than the results from other tests and suggest ideas for diagnosing arrester behaviour.