Locating Faults on Energized Airfield Lighting Power Cables

Sammanfattning: The purpose of this study is to investigate the feasibility of both online and offline fault location and state of health technologies for airport series circuits used to provide power to light fixtures on the runway. In current series circuits, only some ground faults can be detected and no automated fault location or state of health features are available. Fault location is currently performed with an isolation tester and a ”divide and conquer”-methodology which is very time consuming and personnel intensive. The foundation of this work is based on an extensive literature study, where fault location and state of health methods used in the power distribution were identified. The method evaluation of the thesis is based on a concept generation methodology by Karl T. Ulrich and Steven D. Eppinger. Technical evaluations were performed with primarily LTspice as a simulation tool, time domain re- flectometry was also tested in the lab and on real series circuits at Arlanda airport. The results reveal that adopting fault location technologies used in the power distribution industry for series circuit fault location is very difficult, mainly due to the current transformers placed on the series circuit and the high-resistance nature of the majority of ground faults. The transformers pose as impedance discontinuities which contribute with significant high frequency attenuation and dispersion, which obstructs the utilization of any high frequency transients for fault location purposes. Ground faults with high resistances in the kΩ-range does not produce any high frequency transients and does not cause significant steady state-deviations which is problematic for impedance based fault location methods. Current state of health methods proved to be time consuming and personnel intensive, but could potentially be beneficial for Safegate engineers who could benchmark existing cable systems when commissioning new series circuits. Although, large scale tests are recommended in order to validate these results. Further research into utilizing Airfield Smart power and each individual fixture for fault location and state of health is also of interest for future work.