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back on the 'surge'

psychicwarrior

 Good morning to all.  Revisiting a surge issue please.

 

Imagine a final circuit (or it could be some equipment cabling e.g to radio mast but Im not familiar so prefer to use a final circuit as the example ) that is fed from a [upfront] SPD protected board . The circuit runs back outside  (across a zone boundary? ), overhead/buried, for some distance (e.g 100m or whatever)  to equipment that is in contact with earth.

 

  • is it true that circuit could introduce a ‘surge' back into the installation just as the DNO supply may at the origin ?
  • in such a case if true, would there need to be another SPD after the final circuit's OPD to cater for this **… or if not where would the SPD(s) go and across which conductors ?
  • what ‘surge’ levels coming back in to the installation might one expect ?

 

e.g. origin----SPD---DB/CU outdoor circuit OPD--- **additional SPD ------ overhead/buried run (100m) ---- [grounded?] outdoor equip (poss with local SPD)

 

Sorry in advance if I am not understanding well enough to ask a coherant question ! :-)

 

Thank you, Habs

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  • 0

    Thanks Graham, Mike.

    I can appreciate that a comparatively short length eg 0.1km of single overhead/buried final circuit cable outside is perhaps not as much a risk, compared to the possible DNO 1km+ of ‘antenna’ delivering it's various nasties.   

    (mapj) “On its own it cannot prevent currents that flow in on one side of the building and out the other”

    That's the bit I think I'm curious about.  In the same way one is trying to arrest a current ‘coming in’ from the DNO supply side, what else is needed to do so for an induced current ’coming back in' from some outdoor lengthy installation circuit etc ?

     

    As an aside and briefly, various manufacturers seem to be suggesting that where there is an overhead DNO supply and regardless if there is an LPS or not employed, a Type 1 SPD should be installed  (poss a t1+t2 combined where appropriate). One has confirmed this to me directly.

     

    Regards

    Habs

     

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  • 0

    Thanks Graham, Mike.

    I can appreciate that a comparatively short length eg 0.1km of single overhead/buried final circuit cable outside is perhaps not as much a risk, compared to the possible DNO 1km+ of ‘antenna’ delivering it's various nasties.   

    (mapj) “On its own it cannot prevent currents that flow in on one side of the building and out the other”

    That's the bit I think I'm curious about.  In the same way one is trying to arrest a current ‘coming in’ from the DNO supply side, what else is needed to do so for an induced current ’coming back in' from some outdoor lengthy installation circuit etc ?

     

    As an aside and briefly, various manufacturers seem to be suggesting that where there is an overhead DNO supply and regardless if there is an LPS or not employed, a Type 1 SPD should be installed  (poss a t1+t2 combined where appropriate). One has confirmed this to me directly.

     

    Regards

    Habs

     

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