Fault location for aircraft distribution systems using harmonic impedance estimation

The demands for `more electric aircraft` will increase the power distribution requirements of future aircraft electrical distribution systems. To increase safety and reduce aircraft maintenance times on the ground, there is also a need for system condition monitoring to quickly identify and locate any electrical faults which may develop. The work presented in this study forms an initial study into the use of power system harmonic impedance measurement for identifying and locating faults within power cables. The method is passive - that is, it does not require the injection of any test signals - and can be embedded into a centralised equipment controller to provide intelligent, real-time diagnostics. The method estimates the harmonic line`line self-impedance at strategic points in the distribution system by measuring load voltage and current at different load distribution points within the network. By combining the harmonic line`line self-impedance estimates the faults can be identified and located within a few cycles. This can, therefore, provide a `backup protection` system, which does not require bus current measurement. It can also provide a measure of the fault location and could therefore be a significant aid to aircraft maintenance. The study derives the theoretical basis of the scheme and provides experimental results from a laboratory prototype to demonstrate the validity of this approach to detect and locate faults within the system.