Metal oxide arresters on distribution systems: fundamental considerations

The authors compare the reliability of metal oxide and silicon carbide distribution arresters by examining the likelihood of failure as a result of moisture leakage and contamination, overvoltages, and lightning surges of high magnitude and long duration. It is found that metal oxide distribution arresters should be highly reliable in most applications because the arresters are far less likely than silicon carbide arresters to fail as a result of moisture ingress and contamination. Metal oxide arresters are more likely to fail as a result of system overvoltages because they conduct current in response to the overvoltages, and for this reason somewhat more care must be exercised in application to match the magnitude and time duration of system overvoltages to the temporary overvoltage capability of the arresters. Comparison of published metal oxide arrester energy absorbing capability against the energy absorbed in lightning surges that have been shown to exist indicates that the probability of failure may be high in areas of high lightning intensity. The authors suggest changes in the ANSI/IEEE C62.11 standard for metal oxide arresters to improve arrester reliability on lightning surges