Behaviour of zinc oxide surge arresters under pollution

This paper presents results of pollution tests with AC voltages which were carried out with a multi-unit zinc oxide arrester. Zinc oxide surge arresters are exposed to heavy thermal and electrical stresses if the porcelain housings of the arrester units are polluted. Together with other environmental stresses such as temporary over-voltages or high temperatures this can lead to thermal runaway of the metal oxide arrester. In the past in pollution research of MOAs a lot of attention was paid to the coupling in of currents at the flanges of a multi unit arrester with the porcelain housings non-uniformly polluted. This has also been taken into account in the ANSI testing standard for pollution tests of MOAs. Although there is no generally agreed standard for pollution testing of MOAs most pollution tests are carried out according to the test procedures given in IEC 507 which only have been proved to be suitable to test the pollution performance of standard insulators