Insulation coordination for a 23 kV medium voltage distribution

The insulation coordination performance of distribution lines may be associated to two events: the direct lightning strokes and the lightning induced overvoltages both of them are attached to the local flash density to ground. Of course there are particular aspects that must be considered, as for instance, the line route, the shielding degree offered by tall structures, trees and many other ones. This paper deals with the possibility of considering flat and perfect conductively soil, associated to the use of the Monte Carlo technique. However, some simplifications were considered. The first simplification is to consider one-conductor line. The insulation withstanding was obtained from the original field three-phase system. The insulating system CFO voltage and its attached standard deviation were obtained from a complete up and down testing procedure, which must take into account the impulse voltage rate of rise. The statistical insulation withstanding of the system considered a symmetric Weibull distribution.