New zinc-oxide elements with a varistor voltage about twice that of conventional ones of the same thickness have been developed by reducing the ZnO grain size with a new additive, which enable a halving of the series number of elements in metal oxide surge arresters. The advanced arresters with these elements for GIS are compact by 40 to 60% in volume compared with conventional ones. The electrical and mechanical performance of the advanced arresters was found to be satisfactory through various evaluation tests such as thermal stability tests, residual voltage tests, seismic tests and long-term stability tests.
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