Impact of Thermal Aging on the Dielectric Properties and Breakdown Strength of Perfluoroalkoxy (PFA) Insulated High-Voltage Cables for Hybrid/Electric Aircraft

Abstract

The increasing adoption of hybrid and electric aircraft calls for the development of high-voltage cabling systems with superior thermal endurance and dielectric reliability. Understanding their aging behavior is essential for long-term performance in extreme environments. This study investigates the impact of thermal aging on the dielectric properties and breakdown strength of perfluoroalkoxy (PFA) insulated aircraft cables. Thermal aging tests were conducted which include exposing aircraft cables to a thermal aging profile for up to 500 h at 280° C. The dielectric properties, including relative permittivity, dielectric loss tangent $(\boldsymbol{{tan}} \boldsymbol{\delta})$, and volume resistivity, were measured at room temperature using the Novocontrol Concept 80 broadband dielectric analyzer over a frequency range of $\mathbf{1 0}^{\mathbf{- 1}} \mathbf{1 \mathbf { 0 } ^ { \mathbf { 6 } }}$ Hz. For AC breakdown strength evaluation, PFA insulation samples were tested under three electrode configurations: sphere-plane, sphere-sphere, and plane-plane. The results indicate that exposure to the thermal profile up to 500 h leads to a gradual decrease in relative permittivity and dielectric loss, accompanied by a noticeable increase in volume resistivity and a slight improvement in dielectric breakdown strength for all electrode configurations. This trend shall be attributed to the structural relaxation and annealing-like stabilization within the semicrystalline PFA matrix which may occur during the initial stages of thermal aging and leads to improved dielectric performance. Further investigations of long-term aging behavior and degradation mechanisms will be conducted in future work to better understand insulation lifetime under prolonged thermal stress.