270 Vdc Arcing at Flight Altitude Pressures: Comparison with Ground Level

Unwanted electric arcing creates numerous undesirable effects including the possibility of severe thermal damage in its vicinity. Eliminating-or at least minimizing-energetic arcing events is an important endeavor of electric-systems designers. Historically, design guidelines have been based on characteristics of, and experience with, arcing under conditions existing in terrestrial environments. Aerospace vehicles create some unique situations including the fact that air pressure can be sufficiently low at flight altitudes to alter arc initiation, propagation, and damage. Because of the reduced gas density at typical flight altitudes of 20,000 – 50,000 ft (6.1 – 15.2 km), electron mean-free-paths are significantly increased leading to a change in the dominant mechanisms of energy transfer into an arc. This difference can significantly alter the electron energy distribution such that arc effects may be altered. Focused experiments were utilized to demonstrate arcing under various scenarios with 270- Vdc aircraft power. Waveforms of relevant electrical parameters and high-speed videos were recorded to show similarities and differences in arcing characteristics at ground-level and at 50,000-ft equivalent air pressure.