A Review of Statistics on Lightning Currents in Relation to the Lightning Incidence of New-Generation Wind Turbines
Abstract
This paper provides a review of current issues, pertaining to the statistical depiction of lightning currents and in relation to the lightning incidence of modern, new-generation wind turbines. Lightning is a stochastic natural occurrence, described by the log-normal distribution. It can be divided into upward- and downward-initiated lightning, which could be further subdivided into the positive and negative polarity : the polarity being that of the charge transferred from the cloud to the ground. Significant differences exist between positive and negative lightning currents, as well as between upward- and downward-initiated lightning strikes. Additionally, some parameters of the lightning currents are statistically correlated, e.g. amplitude and front duration. All these features are addressed in this paper. Furthermore, it has been established that wind turbines as tall and exposed structures are rather prone to lightning strikes. With heights exceeding 100 meters they initiate their own upward lightning to some extent, as will be hereafter illustrated. This bears consequences on the wind turbine lightning incidence and will subsequently have influence on the selection of lightning currents pertaining to their overvoltage protection analysis.
