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BS7671 history and the future?...
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<blockquote data-quote="Rob_the_rich" data-source="post: 451303" data-attributes="member: 8419"><p>here is the proposed reg again</p><p></p><p></p><p>in TT systems this may mean putting in an additional rod, since even though the distributor does not provide an earth, the requirement is to prevent the dangerous touch voltage, and the main connection to earth is to the original rod.</p><p></p><p>Also, without doing the calcs, the limiting factor is not the disconnection time (as in ADS), but limiting the voltage appearing on earthing conductors under fault conditions to under 50V, during loss of main earthing. A 2 fault scenario. The resistance of the additional rod would need to be extremely low, perhaps impossibly so.</p><p></p><p>Have I got this right?</p></blockquote><p></p>
[QUOTE="Rob_the_rich, post: 451303, member: 8419"] here is the proposed reg again in TT systems this may mean putting in an additional rod, since even though the distributor does not provide an earth, the requirement is to prevent the dangerous touch voltage, and the main connection to earth is to the original rod. Also, without doing the calcs, the limiting factor is not the disconnection time (as in ADS), but limiting the voltage appearing on earthing conductors under fault conditions to under 50V, during loss of main earthing. A 2 fault scenario. The resistance of the additional rod would need to be extremely low, perhaps impossibly so. Have I got this right? [/QUOTE]
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