Computation of thermo-chemical phenomena related to high temperature HPFF cable operation

We report transient nonlinear finite element computations of the coupled electric and thermal fields undertaken to explain defect-induced thermal runaway of an HPFF cable under highly accelerated test conditions. These computations include the effects of temperature and moisture dependent tan(δ), temperature dependent evolution of moisture, temperature dependent evolution of CO, and temperature dependent saturation concentration of CO. Computations were also undertaken for a range of boundary conditions. Comparison between the computed results and measured data suggest the appropriate boundary conditions for such computations. We conclude that thermal runaway probably occurred locally, so that axial heat flow down the conductor results in substantially constant conductor temperature during thermal runaway