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A Micro-Computed Tomography Investigation of the Breakdown Paths in Mica/Epoxy Machine Insulation
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
ABB Corp Res, SE-72178 Vasteras, Sweden.
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2018 (English)In: IEEE transactions on dielectrics and electrical insulation, ISSN 1070-9878, E-ISSN 1558-4135, Vol. 25, no 4, p. 1553-1559Article in journal (Refereed) Published
Abstract [en]

X-ray computed tomography is a technology capable of visualizing a wide variety of materials in 3D. In this investigation, insulation samples were electrically aged and computed tomography imaging was used for analysis of the microstructure and breakdown paths. Samples consisting of mica tape wrapped around aluminum tubes and impregnated with epoxy resin were produced. Two samples were electrically aged at 40 kV(rms) AC and another two at 30 kV(rms) AC until electrical breakdown. The samples were then scanned and reconstructed using x-ray micro computed tomography. The reconstructed images were analyzed and used for rendering volumetric 3D-models of the breakdown channels in the insulation. The results of mu-CT investigation show the location of vaporized insulation as well as the directions of the breakdown paths. When inspecting the 3D models, it is possible to follow the breakdown from electrode to electrode. The results also show that the mica tape layers will act as barriers forcing the breakdown path to follow the epoxy resin layers. It is noted how the breakdown path takes a tortuous course around the mica tape layers and how resin pockets inside the insulation weaken the insulation. Conversely, an improved continuous coverage of the mica tape without wrinkles would improve the insulation properties.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2018. Vol. 25, no 4, p. 1553-1559
Keywords [en]
breakdown, composite, micro computed tomography, epoxy, mica, machine insulation, winding, x-ray
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:uu:diva-364005DOI: 10.1109/TDEI.2018.007083ISI: 000441931200049OAI: oai:DiVA.org:uu-364005DiVA, id: diva2:1260789
Available from: 2018-11-05 Created: 2018-11-05 Last updated: 2018-11-05Bibliographically approved

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Gamstedt, E. KristoferAfshar, Reza

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