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The results of the physical modelling of the formation processes of upward discharges from grounded objects in the artificial thunderstorm cell's electric field are presented. We established the considerable influence of the electrode tip's radius on the pulse streamer corona stem's parameters and, subsequently, on the probability of the transformation of the impulse streamer corona first flash's stem into a first stage of upward leader. We determined the diapason of the optimal tip radii for a lightning rod or lightning conductor, which allows for the most probable formation of the first impulse streamer corona, with the parameters providing the best conditions for the upward leader's start, the purpose of which is the lowering of the probability of lightning striking the object under protection. A considerable difference between the electrical characteristics of the first impulse corona flash with and without the streamer–leader transition was established. It was shown that the amplitude of the streamer corona flash current impulse is considerable, but not the main defining factor of the streamer–leader transition. It is established that the charge value of the streamer corona first flash is not a threshold requirement for the formation of the upward leader from a ground object, but only defines the probability of the successful upward leader formation. Based on the analysis of the experimental data received, we suggest that there is a dependency between the probability of upward positive leader formation from the grounded objects and the charge value of the first pulse streamer corona flash for the rod (centered) and rope (elongated) lightning conductors and objects in the electric field of the thundercloud and downward lightning leader. The obtained results can be used for mathematical modelling of the formation processes of upward discharges from grounded objects in the artificial thunderstorm's electric field, as in a natural thunderstorm situation. [ABSTRACT FROM AUTHOR]

The results of the physical modelling of the formation processes of upward discharges from grounded objects in the artificial thunderstorm cell’s electric field are presented. We established the considerable influence of the electrode tip’s radius on the pulse streamer corona stem’s parameters and, subsequently, on the probability of the transformation of the impulse streamer corona first flash’s stem into a first stage of upward leader. We determined the diapason of the optimal tip radii for a lightning rod or lightning conductor, which allows for the most probable formation of the first impulse streamer corona, with the parameters providing the best conditions for the upward leader’s start, the purpose of which is the lowering of the probability of lightning striking the object under protection. A considerable difference between the electrical characteristics of the first impulse corona flash with and without the streamer–leader transition was established. It was shown that the amplitude of the streamer corona flash current impulse is considerable, but not the main defining factor of the streamer–leader transition. It is established that the charge value of the streamer corona first flash is not a threshold requirement for the formation of the upward leader from a ground object, but only defines the probability of the successful upward leader formation. Based on the analysis of the experimental data received, we suggest that there is a dependency between the probability of upward positive leader formation from the grounded objects and the charge value of the first pulse streamer corona flash for the rod (centered) and rope (elongated) lightning conductors and objects in the electric field of the thundercloud and downward lightning leader. The obtained results can be used for mathematical modelling of the formation processes of upward discharges from grounded objects in the artificial thunderstorm’s electric field, as in a natural thunderstorm situation.

There are existing techniques for building; lightning protection for tall buildings, however, the design of an effective system requires a different approach from the typical one developed for houses or normal size buildings. This category includes skyscrapers and wind turbines, whose number is rapidly increasing. The number of upward, positive strikes and ones that strike into the side of the tower are not negligible. In the latter case, the increasing nominal power increases the dimensions of the turbine, and the risk of a strike, too. Therefore, their expected lifetime may be shortened, and the classical space calculation models have to be rethought and refined. In this work, the probability modulated attractive volume method is applied to examine wind turbines with one and two receptors. Besides that, some investigations of high buildings for negative and positive lightning were evaluated to determine the change of the attractive space. For the risk calculation, the knowledge of the ratio of the striking distances is necessary, which can be determined based on laboratory measurements. The deficiency of each arrangement is demonstrated through simulations and laboratory measurements. [ABSTRACT FROM AUTHOR]

The increased use of electronic equipments in day-to-day life as well as the steady increase in the height of the structures have considerably increased the lightning threat. As a result, a suitable lightning protection system has become very essential. For a reliable evaluation of the protection efficacy the process involved with the final bridging needs to be accurately ascertained. This requires tracing of the inception as well as the propagation of the upward connecting leaders from both the protection system as well as the structure being protected. Owing to the complexity of the problem, only the macroscopic models seem to be practical. As a first step in this direction, the present work has developed a model capable of ascertaining the inception of the upward leaders from both the air termination network as well as the structure itself. In this, the discharge activities around the prospective inception regions are represented by a corona envelope, which is followed by a streamer. Using the works based on the long air-gap switching surge breakdown experiments it is shown that the streamer in the model must attain a critical length for the inception of a leader. This critical length is shown to be sensibly independent of gap-geometry and the electrode radii when varied below the critical radii. The applicability and the stability of the model is demonstrated with a few salient examples. [ABSTRACT FROM PUBLISHER]