Abstract
After a century of practice, cellulose insulating polymer (insulating paper/pressboard) has been shown to be one of the best and most widely used insulating materials in power transformers. However, with the increased voltage level of the transformer, research has focused on improving the insulation performance of the transformer’s cellulose insulation polymer. Considering the complex environment of the transformer, it is not enough to improve the single performance of the insulating polymer. In this study, a nano-structured ZnO-Al2O3-PTFE (polytetrafluoroethylene) multifunctional film was deposited on the surface of insulating pressboard by radio frequency (RF) magnetron sputtering. The effect of the multilayered ZnO-Al2O3-PTFE functional film on the dielectric and water contact angle of the cellulose insulating polymer was investigated. The scanning electron microscopy/energy dispersive spectrometry (SEM/EDS) showed that the nano-structured ZnO-Al2O3-PTFE functional film was successfully deposited on the cellulose insulation pressboard surface. The functional film presented an obvious stratification phenomenon. By analyzing the result of the contact angle, it was found that the functional film shields the hydroxyl group of the inner cellulose and improves hydrophobicity. The AC breakdown field strength of the treated samples was obviously increased (by 12 to ~17%), which means that the modified samples had a better dielectric insulation performance. This study provides a surface modification method to comprehensively improve electrical properties and the ability to inhibit the moisture of the cellulose insulating polymer, used in a power transformer.
Highlights
After a century of practice, cellulose insulating polymer has been shown to be one of the best and most widely used insulating materials in transformers [1,2,3].For cellulose insulation polymer-based transformers, the cellulose insulation polymer itself has poor heat dissipation and the air gap in the fiber reduces its dielectric strength, so the cellulose insulating polymer needs to be immersed in the insulating oil
This study provides a surface modification method to comprehensively improve electrical properties and the ability to inhibit the moisture of the cellulose insulating polymer, used in a power transformer
The Scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) show that the nano-sized particles were attached on the pressboard surface, and The the three-layer, nano-structured functional film was successfully fabricated
Summary
After a century of practice, cellulose insulating polymer (insulating paper/pressboard) has been shown to be one of the best and most widely used insulating materials in transformers [1,2,3]. The cellulose chain between the hydrogen bond, is destroyed because of the reduction of the hydroxyl group, leading to a decrease in the overall mechanical strength of the insulation paper. Polytetrafluoroethylene (PTFE) has good insulation properties, corrosion resistance, and hydrophobic properties It prevents moisture in oil from entering the insulating pressboard [32,33,34,35] and, on the other hand, it can protect the functional layer of the inner layer from being damaged [33]. The functional, thin film successfully improved the electrical properties of the cellulose insulating polymer and its ability to inhibit moisture
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