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The surge degradation of zinc oxide elements under a constant ac stress is investigated experimentally. The results are summed up in a set of formulae and figures from which the degradation of any given condition can be evaluated. The increase ratio of leakage current from the initial value is successfully sed as the indicator of degradation of elements.(More)
SF6 gas has outstanding dielectric strength and heat transfer property. This suggests that zinc oxide (ZnO) elements whose value of E in E-J characteristic is higher than the value of the elements used in a porcelain type arrester is suitable to metal enclosed metal oxide surge arresters (MOA) for gas insulated switchgears (GIS). Several kinds of newly(More)
Metal oxide surge arrester (MOA) is constructed by a series connection of zinc oxide elements having a highly nonlinear resistance. A simple equivalent circuit is proposed to express the dynamic characteristics of zinc oxide element. Using this dynamic model, the effect of lightning strokes to gas insulated substations (GIS) is analized by a computer(More)
The thermal runaway process and the long term degradation of metal oxide blocks for a surge arrester are investigated both experimentally and analytically. The critical condition of a thermal runaway of the blocks is formulated. The dynamic stability after surge absorptions is also studied. The stability limit is given as a function of the temperature rise(More)
Metal Oxide Arresters (MOA), constituted by zinc oxide sintered elements, are the revolutionary advanced surge protective devices for power systems. The newly developed heavy duty elements ensure the high reliability of MOA. Especially, the entirely simplified construction of SF6 gas filled metal enclosed MOA enables the effective insulation coordination(More)
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