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Anonymous Poster

Earthing Resistance Calculations

08/13/2009 11:52 PM
Hi All,

I have few doubts about earth tests. Our refinery has about 10 substations for each area and the earth grid is one for the whole refinery. We do Low Current Injection testing for the whole site every 5 years But what sort of Preventative maintenance strategies do we implement annualy just to make sure the bondings of the earth conductor. Every sub has 4 earth bars and 2 test wells. Should we check the continuity from these earth bars or do we check them from the test well near each sub. Can we also check the continuity between the main earth bar and random structures like tanks, pipes and motors to make sure that the resistance is less than 0.5 ohms. Replies will be appreciated. Thanks
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PWSlack
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#1

Re: Earthing Resistance Calculations

08/14/2009 3:47 AM

In some installations, earth conductors are doubled and parallelled, and a link is present in each one so that, when one of the links is removed, a simple continuity test between the open ends of the link will confirm that both earth conductors are connected at both ends via the second link. Is this the sort of thing that is suitable?

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Anonymous Poster
#2

Re: Earthing Resistance Calculations

08/15/2009 6:26 AM

hi , your test well nesr ea. sub. should be your main starting test points. and in case of uncertainties ( not normal results ) then you can go deeper / further and test / check continuity from the earthing bars.

-- also i recommend physical viewing of the connecting points to check for rust / corrosion and loose connections at random structures like tanks, pipes and motors .

let me know, rgds, marc Hadid, eng, www.mvapower.com ,tel.450 589 0445 x 224
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