Abstract
Epoxy resin-impregnated insulation paper (RIP) composites are used as the inner insulation of dry condenser bushing in the ultra-high voltage direct current (UHVDC) power transmission system. To improve the dielectric properties of RIP, nano-SiO2 is added to the insulation paper at concentrations of 0–4wt % before impregnation with pure epoxy resin. X-ray diffraction (XRD), scanning electron microscopy observations as well as the typical dielectric properties of relative permittivity, DC volume conductivity, DC breakdown strength, and thermally stimulated depolarization current (TSDC), were obtained. The effects of trap parameters on the breakdown field strength and volume conductivity were investigated. The DC breakdown electric field strength of the sample increased as the trap level increased. The maximum DC breakdown strength of nano-SiO2-modified RIP was increased by 10.6% the nano-SiO2 content of 2 wt %. The relative permittivity and DC volume conductivity were first decreased and then increased with increasing nano-SiO2 content. These changes occurred near the interfaces between nano-SiO2 and RIP. The increased DC breakdown strength was mainly attributed to the increased trap level.
Highlights
Direct-current (DC) transmission systems have smaller line losses and can be more economical in long-distance transmission than alternating-current (AC) transmission systems; the demand for long-distance transmission such as new energy grid-connected, offshore wind power and trans-sea transmission
The capacitor core of a high-voltage dry DC bushing is made by alternately rolling a multilayered crepe paper and aluminum foil around the center conductor, vacuum-impregnating the paper with epoxy resin and applying a staged curing process
The main insulation is provided by epoxy resin-impregnated paper (RIP)
Summary
Direct-current (DC) transmission systems have smaller line losses and can be more economical in long-distance transmission than alternating-current (AC) transmission systems; the demand for long-distance transmission such as new energy grid-connected, offshore wind power and trans-sea transmission. High voltage is required as transmission power increases. High-voltage DC bushings are key components for DC transmission systems. Dry DC bushings provide excellent mechanical and thermal resistance and avoid flammability problems of oil-impregnated paper bushings. The installation angle is more flexible than that of oil-immersed paper insulating bushings. The capacitor core of a high-voltage dry DC bushing is made by alternately rolling a multilayered crepe paper and aluminum foil around the center conductor, vacuum-impregnating the paper with epoxy resin and applying a staged curing process. The main insulation is provided by epoxy resin-impregnated paper (RIP)
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