Performance Evaluation of 20 Years Old ZnO Surge Arresters Based on Laboratory Tests

Station ZnO surge arresters have been in service in 800 kV Brazilian substations for more than 20 years. There are also cases of some spare units of such arresters that have been stored for long time without being electrically stressed. As part of investigations about possible causes of a failure occurred in an important Brazilian 800 kV substation, old 800 kV ZnO arresters removed from service, as well as an unused spare, were tested in laboratory. Partial discharge, leakage current and residual voltage tests were carried out on each arrester section at CEPEL´s high voltage laboratory. Just one from a group of three 20 years old arresters removed from service presented acceptable performance. The unused spare arrester presented test results compatible with new ones.