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db/cu and 521.5.1 Ferromagnetic enclosures: electromagnetic effects

psychicwarrior

a good day wishes to all

 

‘they’ do not write these things for no reason; there is science present, so …

using this example: what's the non-compliance issue, if any in reality, with meter tails entering a db/cu through the same opening (fair enough), but a main earthing conductor being glanded/bolted to the housing inside (via a different aperture to the tails, to the earthbar attached to the case, along with bonding etc),  or even on the outside  ?   

 

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    I wonder if the intention behind 521.5.1 is only about thermal heating under normal conditions? The inclusion of the protective conductor in the requirement (which normally would only carry thermally insignificant currents)  might suggest they might have had something else in mind too.

    I've been wondering if separating the line conductor and c.p.c. with ferrous material might increase the reactance of the circuit when large currents are involved? (Those here with a better knowledge of the underlying theory might be able to enlighten us). If so that might have the potential to reduce fault currents/increase disconnection times beyond what would be estimated from R1+R2 tests or low current Zs tests.

        - Andy.

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  • 0

    I wonder if the intention behind 521.5.1 is only about thermal heating under normal conditions? The inclusion of the protective conductor in the requirement (which normally would only carry thermally insignificant currents)  might suggest they might have had something else in mind too.

    I've been wondering if separating the line conductor and c.p.c. with ferrous material might increase the reactance of the circuit when large currents are involved? (Those here with a better knowledge of the underlying theory might be able to enlighten us). If so that might have the potential to reduce fault currents/increase disconnection times beyond what would be estimated from R1+R2 tests or low current Zs tests.

        - Andy.

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