Enhancement of Water Tree initiation due to residual and applied Mechanical Strain on XLPE Cables
DOI:
https://doi.org/10.5324/nordis.v0i23.2453Keywords:
XLPE Cable, mechanical tension, water treeingAbstract
This paper present results from laboratory water tree experiments performed on samples of commercial available 6/10 kV XLPE insulated cables. The main purpose of the investigation was to examine possible water tree enhancement, due to mechanical tension of the insulation
During water tree ageing at 50 Hz AC voltage of 14 kV (E_max = 5.2 kV/mm) the cable samples were mechanically stretched at 1%, using both static and dynamic mechanical load varying at 0.1 Hz. In addition, thermal treatment indicated a total residual longitudinal mechanical strains of 6%, frozen in during th emanufacturing process.
Both the density and growth rate of vented and bow-tie water trees was found to increase with increasing applied mechanical tension. During non-strained thermal treatment the axial length of cables was reduced by about 6%. The low density of vented trees originating from te outer insulation screen supports the assumption that frozen in compressive stresses at the outer insulation surface may balance the effect of applied strain.
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