Experimental assessment of PTFE post-arc ablation

The study addresses the post arc ablation (PAA) of PTFE material used for High Voltage circuit breaker applications. The PAA phenomenon has to be understood in a reliable manner for the development and the optimization of the self-blast circuit breaker, especially for the accurate prediction of the dielectric recovery phase. The experimental activity consisted in generating a high current arc in a PTFE tube and in characterizing the post-arc ablation process. Arcs were generated in ambient air applying AC and DC current to reach current densities in the range 10 7 -10 8 A/m 2 . The characterization has been performed essentially based on standard optical measurement techniques. The shadowgraph technique enabled to show that the post-arc ablation flow is composed by a significant amount of soots, produced within the PTFE tube for several dozens of milliseconds after current interruption. The pyrometry technique enabled to estimate the soot temperatures which was found to be in the range 1400-2200 K. From the empirical data analysis, the post-arc ablation rates were inferred based on rough approximations.