Grounding of distributed low-voltage loads: The street lighting systems

Abstract

Street lighting installations are publicly accessible electrical pieces of equipment out of the physical control of who operates/owns them. Street lighting systems are a typical case of low-voltage loads, distributed in a large area and collectively protected by the same protective device. In fault conditions, hazardous potentials may appear on the metal parts of such equipment, and expose persons to shock hazards. To reduce such risk, different solutions for the grounding are available. The Standard IEC 60364, and a current worldwide tendency, seem to encourage the use of Class II components, that is, equipment with double or reinforced insulation, for all the elements of the street light system (i.e. wiring systems, light fixtures, etc.). These authors examine possible technical alternatives in light of IEC standards, and propose to increase the safety of Class II metal poles by adopting a circuitry within lighting systems panelboards to monitor their double insulation-to-ground.