Abstract:
Paper insulated cables were the first commercially
used cables and they continue to be in service even today owing
to their long history of reliability. Under repeated load cycling
and varying electric stress and temperature, however, the
dielectric properties of the cable undergo changes. In this
work, the relative permittivity of paper insulation from a used
and aged oil impregnated paper cable has been measured at
different electric fields and temperatures using dielectric
spectroscopy. Electric field along the radius of the cable has
been obtained using a software based on finite element method.
The results obtained through dielectric spectroscopy have been
used to input the properties of the cable paper insulation in the
software. A comparison of the radial electric field distribution
inside the paper cable has been made for two cases; one where
the relative permittivity of insulation is dependent on
temperature and electric field and the other where it is
independent. The results of this work may prove to be useful
for monitoring of ageing cables and for cable joints involving
paper cables.
