Electrical Characterization and Modeling of High Frequency Arcs for Higher Voltage Aerospace Systems

Arcing in future high-voltage aerospace systems could occur more frequently and cause irreversible damage to electrical components and system structure, and increase the risk of fire. While arcs seen in low-voltage aerospace systems tend to be long-duration and low-energy events, higher-power but short-duration arcs may occur in high-voltage aerospace systems if they are readily detectable by system protection. This article investigates the characteristics of high current arc faults generated at the ac frequencies expected in future rotating machines used for higher voltage aerospace systems. As such, arcs with a peak current up to 4.6 kA are generated at frequencies in the range of 0.5–2 kHz using an underdamped RLC circuit, under pressures of 0.2–1 bar absolute. High-frequency arcs exhibit a similar characteristic to lower-frequency arcs. A reduction in pressure results in lower arc voltage and arc power. Arcing tests at atmospheric pressure may therefore represent a worst-case scenario and the development of a low-pressure test environment may not be necessary. A black box model is developed to provide good agreement with experimental arc voltage waveforms for different parameters investigated in this study. This is a generalized modeling approach to estimate high-frequency high-voltage arcing characteristics without recourse to experiment.

I. Introduction

Decarbonization is considered an essential pillar in creating a more sustainable environment as part of the European Green Deal [1]. Direct emissions from the aviation sector are responsible for approximately 2% of global greenhouse gas emissions [2]. There is an urgent need to develop aircraft with electrical systems operating at higher voltages to enable the power levels required in all-electric or hybrid electric propulsion systems [3]. With the need for future aerospace electrical systems to be power-dense, there is a continued effort to increase the operating voltage of these systems. According to [4], future hybrid aircraft are expected to see an increase in the power demand up to 5 MW, which raises the operating system voltage to 1–3 kV. Self-contained networks, where generation, distribution, and transmission are achieved on-board give ac power generation an advantage with variable frequency systems going up to 2 kHz to reduce the weight/size of electrical machines [5]. Previous work has shown that while the introduction of higher voltage power systems in aircraft enhances their efficiency, this has also introduced an increased probability of high-voltage faults that could lead to arcs and major failures in aircraft electrical systems [3]. As with any electrical system, there is an expectation that faults will occasionally take place in insulation systems and arcs will develop as a result. Managing arcs that arise from electrical faults in aerospace electrical systems has previously been challenging given the lower operating voltage of the electrical system and low levels of fault current [5]. This has resulted in aerospace cabling systems being designed to withstand the effects of sustained arcing due to wiring faults.