Advanced protection techniques against electrical arc for aeronautic applications based on parameter identification and data analysis
The aviation industry is developing the next generation of more electric aircrafts (MEA) pointing towards the concept of All Electric Aircraft (AEA), which are lighter, more efficient and environmentally friendlier. Architecture advances, including a suitable selection of the power offtake location, minimization of engine bleed requirements, elimination of gearboxes when possible, or transition towards electrical powered solutions, can significantly optimize the power requirements of the engines, thus improving fuel efficiency.
The MEA concept involves a gradual introduction of electrical systems to substitute on-board pneumatic and hydraulic systems used for powering landing gear systems, flight controls, anti-ice systems, brakes or thrust reversers, as well as to pressurize the cabin or for starting the engines.
Next aircraft generations will make a more intensive and efficient use of electrical power. They will apply much higher voltage levels, so the bus voltage will reach 3kV-DC to minimize current requirements and weight. These voltage levels, can be unsafe due to the severe environmental conditions. The dielectric strength of air is greatly reduced at low pressure, generating ionization phenomena, partial discharges (PDs), and ageing of electrical insulation, tending to produce arc tracking, type of PD leading to carbonization paths along the insulation surface of wiring systems, generating leakage currents and producing irreversible insulation damage, thus ultimately leading to arcing phenomena.
There is an imperious need to evaluate the severity of insulation faults in existing installations, since it is vital for ensuring a safe, reliable and stable operation of aircraft power systems.
Electronic arc fault circuit breakers (AFCBs) are being used by existing commercial aircrafts to protect cabling systems against arcing effects generated due to wire insulation faults. Several factors, including inverter noise and switching harmonics, antenna effect, crosstalk or system topology among others, impact the arc signal, thus producing false trips. AFCBs use is problematic, thus requiring new developments to ensure an early detection of very incipient faults.
Due to the increased proportion of electrical power in next generation MEAs, insulation materials must withstand increased electrical stress levels, thus being more prone to discharge activity. The project will develop knowledge of the mechanisms leading to arc tracking, as well as the effects and possible remedial actions to neutralize or minimize arc tracking occurrence. Existing AFCBs are unable to locate the discharge sources and they react after arcing occurrence, when insulation has suffered some level of damage, but do not anticipate the fault condition. There is a need to develop specific electrical protections to detect PD and/or corona activity well before arc tracking occurrence, thus safeguarding electrical wiring systems and aircraft integrity. For this purpose, it is necessary to develop fast response, small-size and cost-effective sensors, as well as specific signal processing techniques specially conceived to operate under aeronautic environmental conditions and to locate the discharge sources before arc tracking is produced. The ArcMaster project will fill these gaps.