Differences in phase, microstructural, and electrical characteristics of quartz-substituted alumina porcelain insulator
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RESEARCH
Differences in phase, microstructural, and electrical characteristics of quartz-substituted alumina porcelain insulator Anil Kumar Kaviraj 1 & Sudipta Saha 1 & Arindam Chakraborty 1 & Gobinda Pahari 2 & Debjyoti Ray 3 & Tapan Kumar Parya 3 & Swapan Kumar Das 3 Received: 14 March 2020 / Revised: 8 October 2020 / Accepted: 13 November 2020 # Australian Ceramic Society 2020
Abstract In the present study, total quartz content (30 wt%) of a standard porcelain body was progressively substituted with two different kinds of aluminas (active alumina and calcined alumina) keeping active alumina constant at 5 wt% and varying calcined alumina content to the extent of 5–25 wt%. The alumina incorporated compositions (AP1 to AP7), along with the standard quartz containing porcelain body (SP0), were processed following common ceramic processing techniques. Two types of forming techniques were used to make samples, namely extrusion of plastic mass to get cylinder of desired dimensions and the other one was hydraulic compaction to produce rectangular bars. The extruded and compacted samples were properly dried and then heated in an electrically operated furnace in the temperature range of 1170–1260 °C. The fully densified samples heated at 1260 °C were subjected to various tests, namely phase identification by X-ray diffraction (XRD) pattern studies; scanning electron microscopic (SEM) analysis; and measurement for electrical properties such as dielectric strength (kV/mm), dielectric loss (tanδ), electrical resistivity (ohm-cm), and dielectric constant to confirm suitability of the samples for application in high-tension power transmission system. The results revealed that the body AP6, wherein 25 wt% quartz was substituted by 5 wt% active alumina and 20 wt% calcined alumina and heated at 1260 °C, may be considered the most suitable sample for porcelain insulator. Keywords Porcelain insulator . Mullite phase . Corundum phase . Microstructure . Dielectric strength . Power transmission
Introduction Electrical insulators are the indispensable components for power distribution system. They prevent or regulate the flow of current in electrical circuits when inserted between conductors. Its internal electric charges, i.e., electrons, do not flow freely, unlike conductors or semi-conductors. It allows flow of current only when it is exposed to a sufficiently high-voltage electric field to tear off electrons from its atom [1]. At present, the popular highest rating of high-voltage AC transmission line is 760 kV as against growing global trend of 1200 kV. So the demand of much improved quality and reliably high-
* Anil Kumar Kaviraj [email protected] 1
Prism Johnson Ltd., Pen Plant, District Raigad, Maharashtra, India
2
Aditya Birla Insulator Ltd, Rishra, West Bengal, India
3
Department of Chemical Technology, Ceramic Engg., University of Calcutta, Calcutta, India
tension electrical insulator with high mechanical strength, high dielectric strength, better resistance towards puncture under polluted and ad
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