Time-domain temperature variations of a composite insulator surface exposed to arc discharges

In this paper, a system of equations is presented, which describes time-dependant temperature variations for a dielectric surface exposed to an arc discharge. The formulas are derived for a circular (as well as any-shape) region interacting with the arc discharge. The final set of equations makes it possible to convert temperature values, measured at some depth beneath the sample surface which is exposed to the arc heating, to the corresponding surface temperature values. The theoretical results are verified by measurements according to the IEC 61621 test method, and numerical calculations are done for an epoxy composition that is used in composite insulator manufacturing.