OF THE VENEZUELAN KERAUNIC ACTIVITY

SUMMARY The results of the initial four (4) years of the implementation of the computerized monitoring system for the detection, location and characterization of the Venezuelan atmospheric lightning discharge activity are presented. These results correspond to years 2000-2003 and are used to construct the first chart of the Venezuelan keraunic activity obtained by means of this data, showing the resultant traditional curves of isodensities of number of discharges to ground per square kilometer per year. The lightning detection system consists of twelve (12) geographically distributed sensors that use the azimuth and the arrival time as well as the intensity to detect and locate the cloud to ground lightning discharges. On the other hand, as it is well known, the lightning discharges affect the behavior of the aerial electrical lines, and the design of electrical transmission lines to assure an adequate number of outages per year, requires not only the information related to the number of discharges per km 2 per year in the zone affected by the line project, but also needs probabilistic information related to the electric current of the lightning discharges that take place, which is usually not provided by the charts. The information about the lightning currents available from the computerized data can be used to perform specific, tailor made, calculations to determine the probabilistic behavior of the lightning currents for the geographic zone affected by the transmission line. A complementary graph is proposed in this work to present this statistical information in a usable fashion. In particular, a family of curves is created using the registered data, each of these curves showing the cumulative probability of the peak or maximum of the lightning currents for each of the density levels defined in the map of ground flash density. The resultant curves are compared with the traditional Anderson-Eriksson lightning discharge current probability curve. It is observed that these curves shift down towards smaller accumulated probability values for the same discharge currents as the density of lightning discharges per year increases. With the proposed complementary graph the standard calculation method for the determination of the expected number of outages per year of the transmission line project is directly applicable using the information provided by the two charts. Finally, sensitivities of the outage rate of a 400kV transmission line were calculated with respect to different parameters and some conclusions are derived. This article has been derived from of the information presented in [1].