Abstract:
In high voltage insulation system, the insulation
will be undergoing various stresses and the life of the insulation
will be different from uniform fields when stressed by a
divergent field. In this paper, dc breakdown experiments at
different step stresses are conducted using needle-plane and
plane-plane electrode systems. Using the data from the
breakdown tests, assessment of life of the insulating material can
be done by estimating the voltage endurance coefficient (n) and
accumulated damage. Stepped-stress damage equalization
method (SSDEM) is used for estimating the life of the insulating
material used. Interesting results on the role of uniform and
non-uniform field on endurance coefficient is reported which in
turn shows the effect of divergent and uniform stress on the life
of the insulation. Furthermore, in this study, a numerical model
is developed to estimate the electric field around the tip of the
needle electrode using a semi-empirical equation of nonlinear
conduction under steady state DC. Spherical geometry system is
used for solving the differential equations numerically. The
results show the developed numerical model can predict the
Poisson’s field when conduction is field dependent.
