Neutral Currents in Large Public Lighting Networks

The modern large public lighting networks are characterized by two major aspects that rise problems from both power quality and neutral current point of view in low voltage wye-connected three-phase electrical systems: (i) the supply system is unbalanced loaded; (ii) the presence of discharge sources. It is important to underline that nowadays, these aspects are not taken into account in the proper sizing of neutral conductors. The paper presents a simplified but enough accurate methodology to estimate the RMS value of neutral currents in lighting networks. The theoretical relationships are illustrated for a three-phase public lighting network that contains high pressure sodium lamps.