Understanding the Influence of Aerospace Operating Environments on Electrical Treeing Phenomenon

It is vitally important to understand the aging and breakdown mechanism of insulation materials prior to any new electrical system introduction. As the world shifts towards more-electric systems in the times of climate change, it is crucial to understand how materials will behave in these new applications. A critical example of this will be electric propulsion in transportation systems, specifically electric or hybrid-electric aircraft. While the power industry understands well the electrical treeing breakdown phenomena in materials like silicone, polyethylene, and other power grid insulators at ambient conditions, there is an apparent lack of literature study regarding the electrical treeing degradation and breakdown under harsh conditions of low pressure and high temperature. However, such studies of the aging of insulation materials under aerospace operating conditions are urgently needed for the safe design and development of more-electric aircraft. In this paper, electrical treeing experiments were performed using Ogura high-precision needles. Cross-linked polyethylene (XLPE) was investigated at ambient conditions as well as at high temperature, with the consideration of the effect of (low) pressure. AC voltage was applied until tree initiation occurred, usually ranging from 10-30kV, and kept constant throughout the growth of the electrical tree. Time until breakdown, tree morphology, and inception voltage were the three main results recorded to probe the treeing behavior trends at different conditions. It was found that at lower pressures and higher temperatures, the tree inception voltage was decreased. The study reveals that harsh conditions, as would be expected during aircraft operation, plays a crucial role on the electrical treeing in insulation systems.