Constellation, le dépôt institutionnel de l'Université du Québec à Chicoutimi

Résumé

The evaluation of the risk of over voltages of atmospheric origin occurring on overhead power supply lines is useful for improving the co-ordination of insulation and electromagnetic compatibility. This paper discusses modelling of positive lightning downward leader and calculation of induced voltages on overhead lines produced by the later in a lightning discharge to ground. The procedure makes use of: (1) a lightning downward leader model based on an equivalent electrical network (a short presentation of the approach is given with a particular attention to the refinements); and (2) a coupling model based on the transmission line theory for field-to-overhead line coupling calculations. Taking into account some atmospheric conditions, the leader model enables to determine its electrical and physical parameters such as current, charge, velocity,… This model allows us to obtain at each step time, the leader distribution of charge along its channel and instantaneous velocity, contrary of the studies performed on lightning leader induced overvoltages, which used a constant value through the propagation. We calculate over voltages induced by very close lightning on a line assuming different strike points in the vicinity of the line. The obtained results are quite satisfactory.