1 INTRODUCTION
CONVENTIONAL Debye model [1-2] is perhaps the most
widely used circuit for dielectric response modeling of oil-paper
insulation. However, the value of branch parameters obtained for
one transformer cannot be used for monitoring the condition of
another transformer, even if their loading history is similar. This
is because every branch of the Debye model represents the
relaxation process of a specific dipole group distributed
throughout the insulation. This makes the branch parameters
dependent on geometry and size of insulation. Unlike branch
parameters of an insulation model, system poles do not depend on
insulation geometry. Fofana et al [3] reported that poles
calculated using insulation resistance and geometric capacitance
can be regarded as an aging sensitive parameter. In the paper it is
shown that poles calculated using insulation model can also be
used for condition monitoring of transformer insulation, provided
that the dielectric response is accurately modeled by the
insulation model.