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Assessment of arc tracking hazards in high voltage aerospace systems

Periodic Reporting for period 1 - ARCTRACK (Assessment of arc tracking hazards in high voltage aerospace systems)

Reporting period: 2019-10-01 to 2021-03-31

As we develop hybrid and all electric aircraft, the voltage level of the onboard electrical systems is expected to climb to 0.75-3 kV (the lower voltages being used for Vertical Take-Off & Landing (VTOL) air taxis and the higher voltages being used in regional jet applications such as the E Fan X demonstrator). Increase in operating voltages, will bring new challenges, such as Arcing. This phenomenon is common in conventional electrical power systems, however its relevance, behaviour and implication in aerospace power systems, is relatively unknown. ARCTRACK project will work towards understanding the arcing phenomenon in aerospace electrical architecture, with findings of the project aiding in improved standards, testing and materials.

The high-level objectives of the entire project are as follows:

Objective 1 – To develop arc models that can be integrated in system level models through experimental test:
Objective 2 – To develop a system level model that allows exploration of arc tracking behaviour in future high voltage aircraft systems:
Objective 3 – To identify changes in the design and protection of aerospace wiring systems that will reduce the risk of arc tracking in future high voltage systems:
Objective 4 – To define experimental methods to verify the arc performance of future high voltage aerospace wiring systems:
in continuation to the objectives and work packages that have been set out in the initial agreement of the project, the progress made so far is highlighted below,

Work Package 1: Phase one has focused on the development of arc models that are suitable for use in the system level modelling package being carried out in WP2. The arc models being used in WP2 must represent the behaviour of the arc over a range of currents and within the environmental conditions expected within future high voltage aerospace systems. A wide range of arc modelling literature has been reviewed and specific arc models down-selected for use in validation experiments. Phase two of the WP is focused on the development of test circuits suitable for the assessment of the level of damage expected to components as a result of arcing events within future high voltage aerospace systems and the ability to ensure damage is localised. So far, testing has been carried out at high current and high frequency at standard and low pressures. The experimental data that has been generated has been to validate the arc models and in turn this has been passed to WP2 for use in the system modelling.
Work Package 2: This WP is led by USTRATH and is focused on the development of reusable accredited models of an aerospace electrical power system, configured to capture the interactions between arc track events and power system technologies. This model will inform the dedicated arc models being developed in WP1 by providing anticipated fault durations and power system fault levels, before becoming the platform for these arc models to be integrated into. It will also be to assess the system level impact of cable technology recommendations made in WP3. Till date, a review of the state of the art in detection and protection techniques for arc track fault events, including dedicated phase-phase and phase-ground detection, has been completed. In terms of the system modelling, reusable, accredited models of E-Fan X and wider hybrid electrical power systems, have been developed specifically for arc tracking fault characterisation in different regions of future electric aircraft.
Work Package 3: This WP is led by TE and is focused on the test of cable materials and cables to evaluate the level of damage that fault currents in the next generation of high voltage aerospace systems could cause. The work is therefore seeking to characterise the cable samples that will be used for experimental test. Data about the cable construction is provided to WP2 and small-scale tests of the materials being used in the next generation of cables will provide information on parameters such as CTI, permittivity, breakdown voltage. Full scale tests using the test rig developed in WP1 are allowing the assessment of a range of cable designs and will demonstrate whether arcs can track in the same way as possible on low voltage systems.
ARCTRACK intends to widen its impact in the areas below,
The development of a clear understanding of arc tracking hazards and mitigation / test measures will give the Topic Manager and the beneficiaries an ability to manage that hazard in an optimal manner (whether this be via cabling design / system level protection measures). The development and test of prototype cable systems will also assist the Topic Manager, Siemens and Airbus to understand the key risks, constraints and opportunities that exist in the flight tests that E Fan X expect to carry out and future commercial products. The simulation toolbox developed during the project will allow the Topic Manager to understand the impact of system level architecture changes on the probability of arc tracking damage.
For the exploration of future electrical architectures: The availability of simulation and experimental techniques regarding arc tracking will be a key enabler for other projects that are exploring new and alternative high voltage architectures for future commercial aircraft. The initiation of changes to existing standards or creation of new standards will assist and federate the development of new hybrid electrical architectures for the wider industry sector.
The aeronautical industry at large including the supply chain will benefit from the clear understanding of arc tracking hazards that will result from this project and the modelling / testing techniques that will be produced by the project. TE will develop a high voltage arc resistant product that will be used in the next generation of high voltage aerospace systems. Recommendations will be made for changes to existing arc tracking standards / opportunities for the development of new standards where appropriate (particularly in relation to system level modelling that is not present at all in the current standard set). The availability of these new / updated standards will be a key enabler as it will provide the certification bodies access to technically sound work that can be used to underpin requirements. The project will also deliver a significant amount of expertise into the aerospace supply chain (engine manufacturer, cable manufacturer, R&D institute and academic partners) on the techniques that are needed for the management of arc tracking. This will therefore result in the ability to reuse ARCTRACK results for other aero applications (current and future).
The recent pandemic has accelerated the aeronautical industry efforts to consider the environmental benefits of electric power over even the most optimised gas engines for commercial sized aircraft, will provide important environmental benefits in terms of noise and pollution reduction especially in certain non-optimised phases of flight (take-off and landing). The Clean Sky 2 Development plan clearly states programme key environmental objectives. ARCTRACK through its contribution to providing enablers for optimised arc track resistance cables which will be used in future electric aircraft programmes will contribute to reducing environmental emissions pollution including CO2 and noise. The value of this contribution is however currently very difficult to quantify.
Aim of ARCTRACK and consortium members