Determination of the probability of a lightning strike in the elements of the object taking into account the statistical distribution of the current value

Abstract

Problem. Modern international standards in the field of lightning protection, when assessing the probability of a lightning strike into an object, do not take into account the statistical distribution of the lightning current. Goal. Justification of the expediency of taking into account the statistical distribution of the lightning current with a determined probability of lightning striking the elements of the object, and the effectiveness of the application of the improved «rolling sphere» method. Methodology. Method of mathematical modeling, based on RSM with additional consideration of the probability distribution of lightning current. Results. The expediency of taking into account the statistical distribution of lightning current at the determined probability of lightning striking the elements of the object has been proven. The effectiveness of the improved «rolling sphere» method, implemented in the form of a computer program, which takes into account the given probability distribution of lightning current in the range from 2 kA to 200 kA, has been proved. The expediency of introducing the concept of «average value of the area of the collection area» is substantiated, taking into account the probability of lightning with a current in a given range. It has been established that the application of the standardized formula leads to a significant (many times) overestimation of the predicted number of lightning strikes to the object, if the height of the object exceeds 20 m. The reasons for the difference, according to the author, are due to the following properties of the standardized methodology: usually, the real shape of the object is not taken into account; statistical distribution of lightning current is not taken into account; it is based on the results of experimental studies obtained mainly for mast or rod-type objects in laboratory conditions with a limited discharge interval. Practical value. This approach will provide an opportunity to optimize the layout of lightning arresters during the restoration of objects, taking into account green reconstruction. The obtained results are proposed for consideration by the Technical Committee TC 81 IEC for inclusion in the next editions of the standards.

Statistical approach for insulation coordination of high voltage substation exposed to lightning strikes

“…Lightning stroke parameters (current magnitude, rise time and tail time) follow a statistical variation assumed to conform to a log-normal distribution, as described in [27][28][29]. The probability density function then takes the following form:…”