Characteristics of Electric Currents in Upward Lightning Flashes From a Windmill and its Lightning Protection Tower in Japan, 2005–2016

Abstract

Upward lightning (UL) from tall man-built structures have received increasing attention during recent years (e.g., reports of Shindo et al. [2012] and IEC TR61400-24 [2019]). It is widely known that an UL is featured with an initial upward leader that originates from a tall grounded structure and propagates toward overhead thunderclouds. UL can be further classified into either positive, or negative or bipolar UL according to the polarity of the charge transferred to the ground (Rakov & Uman, 2003). The UL initial leader, either polarity, is usually followed by the initial continuous current (ICC) with a duration of several hundreds of milliseconds and a peak value over several kilo amperes (Miki et al., 2005). In most cases, more intensive current pulses with a rise time of a few microseconds are found to be overlaid on the slow-varying ICC and referred to as ICC pulses. After the cessation of ICC, dart-stepped leaders and return strokes may occur. So far, either some components or the general features of the current records of UL under different climate conditions have been studied and reported by many researchers from all over the world (e.g.

Observation and Simulation of Lightning Strikes in an Offshore Wind Turbine Cluster

“…Besides, there are some upward lightning discharges in WTCs (Becerra et al., 2018; G. Diendorfer et al., 2011). The shielding effect may be weak on upward lightning (X. Wang et al., 2021), and because the stroke peak currents of upward lightning are usually weak, these may result in a smaller change in the average density of weak strokes than that of strong strokes in the IA.…”