An innovative approach for resin infusion and impregnation processes of a commercial resin-impregnated paper bushing
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ORIGINAL ARTICLE
An innovative approach for resin infusion and impregnation processes of a commercial resin-impregnated paper bushing Zafar Namazian 1 & Mahmood Yaghoubi 1 Received: 17 December 2019 / Accepted: 13 July 2020 # Springer-Verlag London Ltd., part of Springer Nature 2020
Abstract In the present analysis, a new experimental pilot plant system for exploring resin-impregnated paper (RIP) bushing technology was conducted. Experimental and numerical studies were carried out on the resin infusion and impregnation processes in the paper condenser core of a RIP bushing. An innovative approach for the molding process (named molding method B) of a commercial RIP bushing was implemented. For this method, the homogeneity of the paper winding process was controlled precisely. The filling process was conducted by gravity due to the difference of heights between two vacuumed chambers and from bottom to top in the mold. The flow front position and infusion time were measured experimentally and used to obtain the axial permeability of the paper condenser core analytically and numerically. The results indicate that the molding methods have a significant effect on the RIP bushing quality, homogeneous filling, and impregnating process time. Also, it was found that homogeneity of the paper winding process and, consequently, uniform axial velocity of resin flow in the radial direction is the most effective factor to eject the air. Finally, it was recognized that the determination of axial permeability in the case of transient flow is novel in comparison with conventional procedures such as Darcy relation of steady flows. By decreasing the paper thickness from 0.3 to 0.2 mm, the permeability decreased from 8.84 × 10−10 to 4.52 × 10−10 m2. The microstructure of the core illustrates that the axial permeability of the crepe paper condenser core is considerably affected by the variation of the paper thickness. Keywords RIP bushing . Infusion and impregnation . Molding . Paper winding . Permeability
1 Introduction Electrical bushings are vital components, and they are widely utilized in electrical power industries and network equipment such as power transformers, distribution transformers, switchgears, circuit breakers, power capacitors, and shunt reactors to transmit the power safely through high-voltage conductors [1, 2]. Presently, electrical bushings are mostly fabricated by two well-known types: oil-impregnated paper (OIP) insulation and resin-impregnated paper (RIP) insulation. Failures of OIP bushings are more common than RIP bushings, and they can lead to explosion and fire due to the presence of oil [3–5].
* Mahmood Yaghoubi [email protected] 1
School of Mechanical Engineering, Shiraz University, Shiraz, Iran
The RIP condenser core is manufactured using layers of crepe paper and aluminum foils, which are wound continuously on a conducting tube or a rod. After the winding process, the condenser core is implemented for several heatingvacuum cycles, and the core is then impregnated with epoxy resin under vacuum an
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