Modeling of Lightning Exposure of Sharp and Blunt Rods

Abstract

Corona characteristics of lightning rods exposed to ambient fields due to cloud charges prior to negative leader descent are analyzed, taking into account rod slenderness and relative air density. A new formula is introduced to account for the effect such corona on upward connecting leader initiation. This quantifies the tendency of a sharp lightning rod towards self-shielding, which can be detrimental to the protection of a nearby object, particularly if this object is less susceptible to corona formation. The effect of corona due to cloud charge fields on the attractive radius of a solitary rod is also investigated. Based on discharge physics, the characteristics of a non-self shielding air terminal are then defined. Since large electrodes are susceptible to deteriorating corona performance due to protrusions and water drops, preference is given to a corona-free rod with the smallest diameter, under cloud charge fields. For tall rods or rods exposed to high ambient fields, however, the required diameter of a hemispherically capped rod may be impractical. The physical approach described in this paper satisfactorily accounts for the lightning performance of competing sharp and blunt rods in a previous field investigation.

Study on Protection Effectiveness of Early Streamer Emission Lightning Protection Systems

“…2. The tip shape of the pointed aluminum rod is kept conformity with [4]. The spark length made by TC is no more than 40 cm.…”

Evaluating the impact of air terminal geometry on lightning intercept efficacy under a strong background electric field

“…More recent theories suggest that the electric field generated by this corona space charge can "choke" the applied electric field hindering further discharges and ultimately preventing or significantly delaying the air terminal from launching an upward leader. 4 This has led to the development of several non-conventional lightning protection systems, such as designs that attempt to shield a structure from a strike by intentionally creating a glow corona (e.g., a dissipation array system). Other systems now feature air terminals that aim to mitigate the formation of this pre-discharge with claims of better perfor-ARTICLE pubs.aip.org/aip/adv mance over their traditional counterparts.…”

The Physical Experimental Modelling of the Formation Processes of Upward Discharges from Grounded Objects in the Artificial Thunderstorm Cell’s Electric Field

“…The exact formation processes of the upward (counterpart) leader in the thundercloud's electric field and of the downward stepped leader from lightning rod/conductor and/or protected object are not yet fully known [2,6,7,10,12,13,[16][17][18][19][20][21][22][23]. The stage preceding leader formation-the stage of creation and development of the impulse corona stem, its transition into the first leader stage, and the subsequent development located between the two main stages of discharge formation in the air (streamer and leader stages) is presently the least studied one.…”