Dielectric strength of crosslinked polyethylene: the effects of the volatile products of the crosslinking reaction

The breakdown field strength of recessed samples of XLPE (cross-linked polyethylene) containing varying amounts of acetophenone and cumene is shown to decrease with increasing sample thickness. This thickness dependence is more complicated than previously observed. The addition of small amounts of acetophenone to XLPE produces a small increase in the dielectric strength. Small concentrations of cumene have no effect. Results from both AC ramp to failure and impulse breakdown can be fit to Weibull distributions. The characteristic values obtained from ramp to failure measurements depend on the ramp rate as suggested by theory