This paper covers investigation results on electrical and mechanical properties of crosslinked polyethylene (XLPE), used as electrical insulation of medium voltage power cables, under thermal ageing stress. The authors have carried out continuous accelerated thermal ageing of cables at four levels of temperatures ranging from 80/spl deg/C to 140/spl deg/C on 18/30 kV cable samples. The measurements include threshold voltage of partial discharges, dielectric loss factor and relative permittivity as a function of ageing time. The mechanical properties are measured before and after the ageing tests. The obtained results show that thermal ageing significantly affects the properties of XLPE.
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