Lightning Protection

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Anonymous Poster	Lightning Protection 09/18/2009 6:14 AM
	We are doing Lightning Protection of a petrochemical complex which includes towers,process vessels,pumps and other equipment by rolling sphere method.We have a query : The NFPA 780 states that "A zone of protection shall be formed where sphere is resting on two or more srike termination devices and shall include the space in the vertical plane under the sphere and between those devices".What does this term resting signify?Does this mean that the sphere should just touch the air terminals (there are several such cases)or it means that it just rests on the air terminals along its(sphere) centerline(Only one possibility)?
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myn1996 Commentator Join Date: Jan 2009 Posts: 62 Good Answers: 4	#1 Re: Lightning Protection 09/18/2009 6:39 AM
	Try to picture a big sphere place on top and supported by the lightning rods. This means that the tip of the rods are touching the surface of the sphere. Note that this is a sphere so picture this 3-dimensionally with at least 3 lightning rods to support the sphere. This is explained more fully with the IEEE standard. Try to get one if you can. __________________ Patriotism is the last refuge of scoundrels
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Anonymous Poster	#3 In reply to #1 Re: Lightning Protection 09/20/2009 11:33 PM
	Can you please elaborate some more on the term "resting".
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jack of all trades Guru Join Date: Sep 2006 Location: Auckland, New Zealand Posts: 8777 Good Answers: 376	#4 In reply to #3 Re: Lightning Protection 09/21/2009 3:46 PM
	Simply put "resting" is just "touching" two or more points. For example if you built a scale model and placed the rolling sphere (represented by say a ball) on the model then it would "rest" on certain points. The curved surface of the ball represents the likely points where the lightning will strike the plant. __________________ jack of all trades
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wareagle Guru Join Date: Jun 2008 Location: Alabama Posts: 1604 Good Answers: 63	#2 Re: Lightning Protection 09/18/2009 5:45 PM
	Google rolling sphere method http://hibp.ecse.rpi.edu/~connor/education/Surge/Presentations/Joe%20Crispino%20-%20Surge%20Presentation.pdf http://www.ptsa.co.kr/image/ifimmg4.jpg Short and sweet.
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Anonymous Poster (1); jack of all trades (1); myn1996 (1); wareagle (1)

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