Evaluation and diagnosis technique for surge arresters

This paper presents the development of a diagnosis technique, used on-site, applied in the evaluation of station type surge arresters, of SiC and ZnO installed in FURNAS' electrical system. Thermovision, leakage current and radio interference techniques were used in on-site measurements. From the field results, a statistical study was made and the surge arresters were classified in four categories: suspect, defective, normal and better conditions. After the classification, to evaluate the minimum characteristics of protection, some surge arresters were selected for laboratory tests (flashover voltage, leakage current and residual voltage). After the evaluation of the results, the equipment were opened. The surge arresters' field diagnosis and their abnormalities were confirmed by the results of laboratory tests and internal visual inspections. It was noticed that for every surge arresters there were abnormalities.