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Active Contributor

Join Date: May 2011
Posts: 18

Electrical Grounding

10/20/2014 1:45 AM

In our gas plant, the EPC install the air terminator rod for the lightning at the top of the condensate storage tank and the metal strip from the air terminator is connected to the storage tank metal body (at the top side). Then the bottom of the metal tank is connected to the ground through the another metal strip. Suppose the lightning will take place on the air terminator, obviously the heavy lightning current will flow through the metal body of the condensate storage tank to the ground. Anybody can clarify to me that this installation whether right or wrong with specified standards.

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Pathfinder Tags: electrical grounding
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Guru

Join Date: Nov 2006
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#1

Re: electrical grounding

10/20/2014 6:15 AM

Two independent metal strip should be run down to earth electrodes at ground .These elctrodes should not be connected other equipment electrodes.Now you are using the tank body as part of the path which in my view is not correct and can be dangerous during a lightening strike.

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Associate

Join Date: Jan 2012
Location: chennai.
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#2

Re: electrical grounding

10/20/2014 6:51 AM

it has to be isolated no doubt for full safety for the storage tank.

But there are different type of isolation methods are there. Extactly in which method they designed the protection. pls Refer the IEC STandard for lightning 62305.

For ciritical storage method i pefer you that go with Rollowing sphere method of protection.

Thanks.

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Prabakar
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Join Date: May 2014
Posts: 5
#3

Re: Electrical Grounding

10/20/2014 11:55 PM

No.He is abosolutely wrong.Down conductor from Air terminator of Lightning protection system should run directly to ground with an exclusive path to an earth pit and not through any looping.The earth pits for system protection should be inter connected to achieve Equi potential Bonding.Referenc to French Standard NFC !7-102

.V.Natarajan

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Active Contributor

Join Date: Jun 2014
Posts: 19
#4

Re: Electrical Grounding

10/21/2014 2:12 AM

Hi,

Putting the metal tank in the path of lightning discharge currents is not good practice. Even if the tank is metal and would allow lightning currents to flow, do also consider that lightning currents may also discharge through the contents of the tank, thereby, breaching any waterproofing that the tank may have, or worse still causing fire if content has low flash point. I would design an air termination network, down conductors and earth termination network accordingly following the applicable codes.

Rgds.

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Guru

Join Date: Apr 2012
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#5

Re: Electrical Grounding

10/21/2014 10:13 AM

NFPA 780 should help out. Make an account at NFPA.org, then you will be able to login and access it for free at NFPA 780.

Your example is not the proper method for a Lightning Protection System. I suggest the aforementioned code, at a minimum.

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Guru

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#6

Re: Electrical Grounding

10/29/2014 12:45 AM

I agree with The.Tinkerer. See NFPA 780/2004 CH.7.4 Protection of Specific Classes of Structures.

However I'd prefer this alternate grounding method:

[NFPA-780/2004] FIGURE 7.3.3.9 Alternate Grounding Methods for Overhead Ground-Wire Protection.

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Julius
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Users who posted comments:

7anoter4 (1); ade_jkrs (1); nesubra (1); sprabakar22 (1); The.Tinkerer (1); V. Natarajan (1)

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