Longitudinal Breakdown Strength of Wet-mate Solid-Solid Interfaces at VLF and 50 Hz AC voltages
DOI:
https://doi.org/10.5324/nordis.v27i1.4897Abstract
The 50 Hz AC breakdown strength of dry interfaces is known to strongly depend upon the mechanical properties, contact pressure, roughness of the surfaces, and the type of lubricant used at the interface. This paper aims to experimentally examine how these factors affect the longitudinal AC breakdown strength of interfaces assembled in water, so-called wet interfaces. The main aim is to obtain data relevant to the design of power equipment operating at very low frequency (VLF) or DC voltages.
Experiments were conducted using identical specimens made from 4mm thick plaques of PMMA and plane sections cut from XLPE cable insulation. The findings were discussed with respect to expected dimensions of interface voids and contact regions, considering tribology-based contact theory, including the impact of surface roughness, modulus of elasticity, and applied mechanical interface pressure.
The longitudinal 50 Hz AC breakdown strength values of wet samples were typically as low as 80 % of samples assembled in the air under dry conditions. In addition, the results verified previous findings that the AC breakdown strength strongly increases with reduced surface roughness, stiffness, and increased interface pressure. The breakdown values obtained during VLF breakdown testing were found to be 2 – 3 times higher than in the case of testing at 50 Hz AC voltages.
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Copyright (c) 2022 Erling Ildstad, Roger Dale, Emre Kantar
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