Abstract:
The surface voltage of an insulator assumes
importance for understanding tracking and flashover
characteristics. Until now, determination of surface voltage of
insulating surfaces is left to simulation software and such
simulations are left unverified experimentally, leading to
uncertainty of the results, which may sometimes be erratic
with improper choice of boundary or initial conditions or
inaccurate material properties, nonlinearities etc. The paper
presents a novel method, using which the surface voltage of
any insulating surface such as insulator strings or transformer
bushings can be measured. Unlike a conducting surface, the
measurement of insulating surface voltage using voltage
dividers would be erratic as the measuring arrangement itself
will vary the voltage division due to the local unknown
impedance between the insulated surface and hv conductor.
Recently a method for measurement of surface voltage of an
insulated conductor using cylindrical strips was reported. In
this paper, based on analytical derivations, a more generalized
method of measurement, applicable to any point on an
insulating surface of arbitrary geometry is proposed using
circular-disc strips. The proposed experimental method is
applied to insulator strings and transformer bushings and
validated by simulation of the entire systems. The simulation
and experimental results are in excellent agreement.
