Live working diagnosis of joints of overhead lines

An assessment of all the surveys of joints for fifteen years indicates that they constitute a weak point in overhead lines. Internal corrosion or a defective realisation is the original cause, which leads, later on, to the increase of the contact resistance and therefore of the temperature of the joint. The authors examine how the joints are made and what phenomena occur in their ageing. This analysis leads to retention of the most influential factors and a proposal for modelling of the joint and of the evolution of its degradation in the past. The authors then describe the ageing prediction capacities made by a model in several selected situations, because they appear in operation. These simulations make it possible to extract the strong tendencies and from them conclusions about the service life of joints. They have repercussions on initial quality and in situ controls of the joints and maintenance of overhead lines. Finally, the authors examine a method of live working measurement of the electric resistance of joints