The impacts of direct lightning bolt on the Ngo-Brazzaville line in Congo

Rodolphe GOMBA, Alphonse OMBOUA

The importance of line Ngo-Brazzaville (220 kV, 207 km) requires operators to avoid cuts that can increase the risk of instability. We see it is quite rare that a storm that occurs in areas crossed by this line will not cause triggering. We note that lightning discharges constitute the main causes of unscheduled power cuts on the electricity lines of Congo; however, we ignore the peak values of voltage waves that result. In regions with high level keraunic like Congo, reducing insulation failures due to lightning is a concern in the management of overhead lines. This article clarifies the peak values of surges that can be reached on the electricity network, in order to enlighten the operators as for precautions to observe about the insulation coordination of protective equipment related to lightning. For these surge’s calculations of atmospheric origin (case of lightning), we considered the Heidler function for modeling the wave of the lightning current. This methodology led us to specially treat the effects of direct   lightning bolt that constitute the worst case because they generate most destructive shock wave that indirect thunderbolt.