High-voltage atmospheric breakdown across intervening rutile dielectrics

The electrical power grid, aircraft, and defense systems are potentially subject to damage from lightning strikes. Surge arresters are high-voltage safety components used to mitigate damage to many critical systems by diverting transient currents to ground via breakdown. Some arresters utilize high-permittivity dielectric materials, such as rutile (TiO₂), to ensure breakdown occurs at a prescribed voltage and prevent a transient voltage pulse from affecting downstream components. Though widely used, the physical mechanisms for surface breakdown in surge arresters are not well understood. Electrical discharge experiments are being conducted to help develop predictive computational models of the fundamental processes of surface breakdown in the vicinity of high-permittivity material interfaces. Discharge path imaging and electrical data are presented. Results are compared to electrostatic calculations using an ionization coefficient-based approach and Townsend-breakdown criteria for non-uniform fields and the observed breakdown path. It is shown that rutile reduced the breakdown voltage of an electrode gap by ~50% even when the visible discharge path did not interact directly with the sample.