Assessment of arc tracking hazards in high voltage aerospace systems
Electrical wiring systems on aircraft have traditionally operated at low voltages (115V AC / 28V DC). The insulation system used in the wiring systems is not subject to significant levels of electrical stress, but thermal and chemical degradation / mechanical damage can allow the insulation to be breached. If two wires / a wire and a ground plane are then breached by a conductive fluid (from a leaking pipe / condensation) or by making contact with a conductive surface (such as a bulkhead), current will then flow.
The magnitude of the current is then limited by the electric arc that forms between the wires with the arc voltage being of a similar magnitude to the system voltage. These arcing events are therefore difficult to detect given their intermittent nature and the relatively small levels of current that flow. However, they can cause significant damage. A recent example was the loss of an F35B where an electrical fault caused by an incorrectly installed bracket then caused the failure of a hydraulic line and a fire.
As we development hybrid and all electric aircraft, the voltage level of the on-board electrical systems is expected to climb to 0.75-3kV (the lower voltages being used for VTOL air taxis and the higher voltages being used in regional jet applications such as the E Fan X demonstrator). The use of higher voltages, the change in component technology (such as using screened instead of unscreened cables), system configuration (grounded / ungrounded) and use of composite structures within the aircraft will all impact on arc tracking.
This project aims to deliver a clear understanding of the arc tracking hazard in these new higher voltage systems and describe ways in which it can be quantified and mitigated.