Influence of the surrounding medium and service behaviour of metal oxide resistors for high voltage arresters

The direct use of metal oxide (MO) resistors as surge arresters without spark gaps is examined. Their behavior in various gas atmospheres, such as can occur due to partial discharges inside the arrester, is discussed. Attention is also given to their behavior in air with decomposition products and SF₆ with decomposition products. Investigations of complete MO surge arresters in a 110 kV system after several years in service are reported, with emphasis on gas composition and leakage current. It is concluded that, by a suitable choice of the material composition, an adaptive control of the production process, and a selected coating, MO resistors which exhibit stable service behavior in reducing gas atmospheres can be produced