Measurement and analysis of partial lightning currents in a head phantom

Abstract

Direct lightning strikes to the human head can lead to various effects, ranging from burnings to death. The biological and physical mechanisms of a direct lightning strike in the human head are not well understood. The aim of this paper is to design an experimental setup to measure the spatial and temporal current distribution during a direct lightning strike to physical head phantoms to establish normative values for personal lightning protection equipment design and testing. We created head phantoms made of agarose, replicating the geometric and dielectric properties of scalp, skull, and intracranial volume. The bases of the three compartments were galvanically contacted via copper electrodes to measure the current per compartment. We used pulse generators to apply aperiodic voltage and current signals that modelled lightning components. Our experiments indicated that the scalp compartment was exposed to the current with a fraction of 80–90%. The brain and skull compartments were exposed between 6–13% and 3–6% of the total measured current respectively. In case of a flashover, most of the current (98–99%) flowed through the discharge channel. Unlike previous theoretical estimates and measurements in technical setups, we observed considerably longer times for the flashover to build up. In our experiments, the time to build up a fully formed flashover varied from approximately 30–700 μs. The observed current patterns in cases without and with flashover provided information on regions of possible damage in the human head. Consequently, we identified the phenomenon of a flashover as a potential mechanism for humans to survive a lightning strike. Our measured current distributions and amplitudes formed the base for normative values, which can be used in later experimental investigations regarding the possibilities of individual lightning protection equipment for humans.

Strom- und Blitzunfälle im Rettungsdienst

“…Ein Blitz hat eine Spannung von bis zu 1 Megavolt (MV) [15] bei einer Stromstärke von bis zu 200 Kiloampere (kA) [15,16] was je nach durchflossenem Medium zu einer Temperatur von bis zu 50 000 °C führen kann [8]. Die Dauer des Stromflusses ist mit wenigen Millisekunden allerdings sehr kurz [17,18].…”

“…der Kopf im offenen Gelände besonders exponiert. Direkte Blitzschläge können Schädelhaut und Schädelknochen durchdringen und unmittelbaren Schaden am Hirnparenchym verursachen [15].…”

Weltweite Unfälle mit Blitzschlägen: regionale Analyse und medizinische Therapie

“…1). Ein Blitz hat eine Span nung von bis zu 1 MV [10,11] bei einer Stromstärke von bis zu 200 kA [11]. Trotz der kurzen Dauer des Stromflus ses von wenigen Millisekunden kann ein Blitz das Medi um, in das er einschlägt, auf mehrere Tausend Grad Cel sius erhitzen [12,13].…”

“…Der Blitzstrom wird oberflächlich abgeführt [17]. Dieses "flash-over phenomenon" wirkt am Kopf besonders pro tektiv, da der Schädelknochen neben der oberflächlichen Haut eine weitere, wenig elektrisch leitende Schicht mit hohem Widerstand bildet [11].…”