The flashovers that occur in electrical insulators are .problems that can shut down the transmission and distribution electrical energy line. Insulators placed in regions with high salinity or atmospheric pollution are more susceptible to failure by occurrences of fiashover. In the present work the effect of the application of a semiconductor coating containing 95 wt% SnO_2 and 5 wt% Sb_2O_3 to high-voltage electrical insulators was studied. The coating was applied by dip coating. The effects of semiconductor coating are ohmic heating and homogeneous electrical current distribution on the surface of the insulator. The properties of developed glazes were analyzed by SEM, XRD, surface resistivity and salt spray chamber tests. The thermal expansion coefficient of the coating was evaluated and matches the bulk one. The flexural strength of the insulator was increased by approximately 13% due to the lower thermal expansion coefficient of the semiconductor glaze which creates surface compressive stresses. Tests in salt-spray chamber showed that semiconductor glazes can develop surface heating of about 55°C and endure large quantities of deposited salt under high-voltage, without the development of flashovers, thus increasing the performance of the insulators.
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