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Logic problem in OSG - trivial

Ziggie
Page 79 OSG (blue edition)


Lcn is max fault current .......although the breaker may no longer be usable.

Lcs is max fault current .......can interupt safely without loss of performance.


.........


For domestic installations, the PFC is unlikely to exceed 6kA , up to which value the Lcn will equal Lcs.


usable , maybe usable, certainly usable?


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  • 0
    when you get into this territory, there will be something before the MCB.

    Indeed, perhaps an energy limiting "death or glory"  fuse, cunningly selected so the I2t (or if you prefer to think of that as joules per ohm) of the fuse means that the (however many milliohms) contacts of the breaker do not get hot enough  (joules) to weld even in the unlikely event of a silver stake zero ohms fault right next to the origin.

    In a domestic situation the company cut-out fuse will perform this damage limiting function to a degree, as well as protecting the tails and the meter.

    M.

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  • 0
    when you get into this territory, there will be something before the MCB.

    Indeed, perhaps an energy limiting "death or glory"  fuse, cunningly selected so the I2t (or if you prefer to think of that as joules per ohm) of the fuse means that the (however many milliohms) contacts of the breaker do not get hot enough  (joules) to weld even in the unlikely event of a silver stake zero ohms fault right next to the origin.

    In a domestic situation the company cut-out fuse will perform this damage limiting function to a degree, as well as protecting the tails and the meter.

    M.

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