Conference Agenda

Polyimide (PI) is extensively used in aerospace applications owing to its exceptional properties. However, exposure to harsh environmental conditions, including heat and humidity, can significantly affect its performance. Understanding the effects of aging on PI is important for ensuring its long-term reliability in aerospace systems. This research presents the impact of thermal oxidative aging and humidity on the dielectric performance of polyimide (PI). Aging was conducted at 250°C for 170 hours under controlled humidity conditions, facilitating thermal oxidative degradation and moisture absorption in polyimide. The results of Scanning Electron Microscopy (SEM) analysis revealed surface degradation in aged PI, characterized by micro-voids and cracks that facilitated moisture ingress into the bulk material. The aging process led to the formation of polar molecules, including moisture-induced hydroxyl groups, which enhanced the polarization ability and AC conductivity of PI. To analyze these conductivity changes, Jonscher's Power Law and the Almond-West formalism were employed. The fitting of AC conductivity data using these models provided insights into the frequency-dependent charge transport behavior in fresh and aged PI. The extracted parameters, including DC conductivity, crossover frequency, and relaxation time, demonstrated that aging resulted in increased charge transport and a shift in the frequency response. While the bulk resistivity decreased, the carrier density and mobility were notably enhanced, leading to an increase in leakage current density. At high electric fields (100 MV/m), the leakage charge density increased by 8.4% due to the aging process. These findings highlight the impact of both thermal oxidative and humidity-induced aging on the dielectric and microscopic properties of PI, which is essential for assessing its reliability in aerospace applications under harsh environmental conditions.

High-voltage circuit breakers (HVCBs) are critical components in power systems. They safely isolate and connect electrical networks. Their primary function is to open or close circuits, controlling electrical current flow under normal conditions and preventing damage during faults. HVCBs interrupt currents from very small values up to the maximum rated short-circuit current. The interruption process uses arc energy to generate gas pressure, which is necessary for extinguishing the arc and preventing re-ignition. The residual arc energy is dissipated through heating and ionization of the surrounding gas, vaporization of metals from arcing contacts, and ablation of nozzles.

Understanding the energy balance in an HVCB is crucial for designing efficient and reliable circuit breakers. This involves determining how the arc energy is distributed among the different dissipation mechanisms. This work investigates the energy balance of an HVCB using computational fluid dynamics (CFD) simulations. The simulations are performed for power test duty with 100% of the short-circuit current (T100a). The results show that the energy balance is complex and depends on several factors and estimating it can highlight necessary design changes to enhance the performance. By using CFD simulations and understanding the energy balance within an HVCB, engineers can develop more reliable and efficient circuit breakers that can meet the demands of modern power systems.