Anode Hotspot Temperature Estimation in Vacuum Gaps under 50 Hz Alternating Excitations

Balachandra, TC and Nagabhushana, GR (1993) Anode Hotspot Temperature Estimation in Vacuum Gaps under 50 Hz Alternating Excitations. In: IEEE Transactions on Electrical Insulation, 28 (3). 392 -401.

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Abstract

This paper presents the computed results of anode hotspot temperature calculations for vacuum gaps subjected to 50 HZ ac excitations. The transient heat diffusion equation governing the heat conduction is solved by a finite difference method. The effects of nonlinear variation of thermal properties with temperature and phase change are also studied by using ANSYS 4.4, a powerful finite element package. The peak temperatures are estimated by a seminumerical method. The methods presented provide a convenient means of anode hotspot temperature estimation and the determination of cool-off time for different electrode materials. The results of a parametric study to examine the effects of electrode material, field intensification factor, and radius of the spot are presented along with a comparative analysis of different available methods. The results obtained for stainless steel, copper and aluminum anodes indicate that the temperature of hot spots can reach the melting point for reasonable values of the field intensification factor.They are therefore the main sources of microparticles. The asymmetry of the experimentally observed prebreakdown current waveform about its own peak, which is caused by thermal instability at the anode, can be attributed to the nonlinear variation of thermal properties with temperature. The methods discussed can be used to estimate the size of microparticles originating from thermally unstable regions at the anode.

Item Type:	Journal Article
Publication:	IEEE Transactions on Electrical Insulation
Publisher:	IEEE
Additional Information:	Copyright 1990 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.
Department/Centre:	Division of Electrical Sciences > High Voltage Engineering (merged with EE)
Date Deposited:	22 Aug 2008
Last Modified:	19 Sep 2010 04:26
URI:	http://eprints.iisc.ac.in/id/eprint/6777

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