Electrical safety of aeronautical ground lighting systems

Aeronautical ground lighting (AGL) systems have been developed to deliver warnings and status indications to pilots and maneuvering area vehicle drivers on runways. Their role in preventing the hazard of runway incursions, present in the aviation industry, is therefore crucial. AGL systems basically consist of: a primary series lighting circuit, which is supplied at constant current and high-voltage (e.g. 5 kV); AGL transformers supplying ground lights at their secondary sides. Protection of persons against electric shock in AGL systems cannot be conveyed by disconnection of supply, as ground-faults would cause the out-of-service of the lighting system, thereby compromising the safety of aerodromes; alternative protective measures are therefore employed. In this paper, the authors examine the electrical safety issues present during maintenance of AGL systems, often performed live in order to guarantee the continuity of the service. Experimental measurements on AGL isolating transformers have also been reported in the paper and possible solutions to improve the electrical safety of operators are proposed.