Experience from exploitation of surge arrester counters

The paper presents experience from exploitation of surge arrester counters. There was documented destructive influence of humidity inside the untight surge arrester counter on its operation and ZnO varistors within. There were presented examinations of microstructure of varistors of damaged surge arrester counters. A point of reference was similar ZnO varistor, not subjected to operation before. Investigations revealed that material of varistors had an untypical phase composition and was characterized by unsatisfying homogeneity and cohesion. There were recognized and described the subsequent stages of the degradation processes of varistors material. Conclusions resulting from the operation checking of surge arrester counters were also presented.