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Title: Internal voltage in a conducting closed hollow cylinder with an attached end plate subjected to a direct lightning strike

Abstract

The interior voltage of a large metal can with thick walls struck directly by lightning was estimated using diffusion theory, aperture slot voltage theory, and experimental data. The hollow cylinder is closed at both ends. One end has a cap that is welded to the cylinder wall making a continuous electrical interface. The other end consists of a circular plate that is pressed into the cylinder wall and held under pressure with a threaded ring. From our experience with coupling measurements, this joint will be a weak link. It will allow more current to leak into the interior than from diffusion through the walls. Because the joint was designed for mechanical purposes, the electrical properties, such as continuity around the circumference, are not well controlled. Therefore, it is difficult to determine a single voltage attributed to this joint design with varying electrical characteristics. Instead, we will make a best effort of bounding the problem using both analytical calculations and data from tests of similar structures. The calculated internal cylinder voltage subjected to an extreme lightning strike from current diffusing through the wall is 19 volts. We estimate that the press-fit end plate will increase this voltage by a factor ofmore » about two to ten. The internal voltage is expected to be between 40 and 200 volts. This uncertainty can be reduced by making coupling and high-current measurements on a number of cans or by redesigning the cap to include electrical contacts. However, given that the critical components inside the cylinder are insulated to at least 3.5 kV, improving the joint design is unnecessary. The safety factor using the worst-case maximum interior voltage is 18 and is sufficient. A higher safety margin can be achieved by keeping the joint clean and under pressure.« less

Authors:
;
Publication Date:
Research Org.:
Lawrence Livermore National Lab., CA (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
15005728
Report Number(s):
UCRL-ID-139665
TRN: US200324%%96
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 1 Jun 2000
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING; APERTURES; DESIGN; DIFFUSION; ELECTRICAL PROPERTIES; LIGHTNING; PLATES; SAFETY

Citation Formats

Ong, M M, and Anderson, R A. Internal voltage in a conducting closed hollow cylinder with an attached end plate subjected to a direct lightning strike. United States: N. p., 2000. Web. doi:10.2172/15005728.
Ong, M M, & Anderson, R A. Internal voltage in a conducting closed hollow cylinder with an attached end plate subjected to a direct lightning strike. United States. doi:10.2172/15005728.
Ong, M M, and Anderson, R A. Thu . "Internal voltage in a conducting closed hollow cylinder with an attached end plate subjected to a direct lightning strike". United States. doi:10.2172/15005728. https://www.osti.gov/servlets/purl/15005728.
@article{osti_15005728,
title = {Internal voltage in a conducting closed hollow cylinder with an attached end plate subjected to a direct lightning strike},
author = {Ong, M M and Anderson, R A},
abstractNote = {The interior voltage of a large metal can with thick walls struck directly by lightning was estimated using diffusion theory, aperture slot voltage theory, and experimental data. The hollow cylinder is closed at both ends. One end has a cap that is welded to the cylinder wall making a continuous electrical interface. The other end consists of a circular plate that is pressed into the cylinder wall and held under pressure with a threaded ring. From our experience with coupling measurements, this joint will be a weak link. It will allow more current to leak into the interior than from diffusion through the walls. Because the joint was designed for mechanical purposes, the electrical properties, such as continuity around the circumference, are not well controlled. Therefore, it is difficult to determine a single voltage attributed to this joint design with varying electrical characteristics. Instead, we will make a best effort of bounding the problem using both analytical calculations and data from tests of similar structures. The calculated internal cylinder voltage subjected to an extreme lightning strike from current diffusing through the wall is 19 volts. We estimate that the press-fit end plate will increase this voltage by a factor of about two to ten. The internal voltage is expected to be between 40 and 200 volts. This uncertainty can be reduced by making coupling and high-current measurements on a number of cans or by redesigning the cap to include electrical contacts. However, given that the critical components inside the cylinder are insulated to at least 3.5 kV, improving the joint design is unnecessary. The safety factor using the worst-case maximum interior voltage is 18 and is sufficient. A higher safety margin can be achieved by keeping the joint clean and under pressure.},
doi = {10.2172/15005728},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2000},
month = {6}
}

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