Although metal-oxide arresters (MOA) were introduced on
the market several years ago, their modeling is still a problem
[l, 2, 31. Several accurate models have been proposed to
describe the arrester behavior for different kinds of stress.
The hard point is the identification of the model parameters,
and the need of field tests or of trial-and error procedures to
determine acceptable values. As a matter of fact, due to these
difficulties only arrester manufacturers or specialized
laboratories have today the real possibility of performing
overvoltage ceordination studies.