High-Voltage Real Capacitance Analysis for Dry-Type Bushings Insulated by Epoxy Resin Impregnated Paper Under Different Moistures

Dry-type bushings insulated by epoxy resin impregnated paper play a critical role in power energy transmissions and conversions. Compared to traditional oilimmersed bushings, the solid polymeric insulation in dry-type bushings have not obtained enough dielectric data under varied external conditions. However, the insulation health condition diagnostics of full-size dry-type bushings become significantly important due to the degradation of insulation materials exposed to harsh operating scenarios like high fields and high humidity. Therefore, this paper performed the high-voltage frequency dielectric spectroscopy measurement and mechanism analysis for epoxy resin impregnated paper insulation systems in dry-type bushing. The evolution rules and potential physical mechanisms of real capacitance would be presented and discussed as a function of measurement voltages and moisture conditions. The relevant evaluation indicators for diagnosing the moisture conditions of insulation systems in dry-type bushings would be proposed. This paper aims to provide basic data support and reference for the qualification tests in manufacture and insulation health condition analysis of dry-type bushings in service.