Fault detection for the aircraft distribution systems using impedance estimation

With the move towards "more electric aircraft" there is a greater need to quickly identify and locate electrical faults within the distribution system. The work presented in this paper forms an initial study into the use of power system impedance measurement for identifying faults types within the power cables. The method is passive - i.e. does not require the injection of any test signals - and can potentially be embedded into a centralised equipment controller to provide intelligent diagnostics. A simplified aircraft distribution system has been simulated. It includes four lumped loads which represent distribution panels ('nodes') connecting the distribution bus to groups of loads. The principle to fault identification employed here is that at each of the four nodes, a high sample frequency data acquisition system (DAS) can be used to measure the voltage at the point of connection and the node current. This DAS can continually perform frequency domain analysis of these measurements and calculate equivalent system impedance. If a fault occurs, at harmonic frequencies the identified impedance changes and this can provide information about fault type and fault location. Simulation results demonstrate the validity of this approach.