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my surge protection 'cpd', such as it is...

psychicwarrior
Good morning all


I have obtained the following [I feel as the] 'best we can do for now' information from the DNO. They were helpful in my test case request for info.


"...address 1:

LV underground - 362m

HV underground to primary-  2000m

No Surge protection devices


address 2:

LV underground to substation - 110 m

HV UG from substation to HV pole is 823m then 301m 11kV overhead then 190m HV UG to the primary substation.

Distance to cable termination with surge protection device from secondary substation is 1124m (823m 11kV UG + 301m 11kV Overhead).  The nearest cable

termination does not have surge protection installed. ..."


In relation to the risk assessment equation variables dealing with distribution cable lengths  ie. the Lpal Lpcl Lpah Lpch, how would one fit the given values into the variables ?


For addr1, ignore the HV (e.g. use zero for Lpah Lpch),  then take Lpcl as 362 and Lpal as 638 ?


For addr2, i'm not sure on this one ?


Thanks for your input.

Habs


  • 0

    AJJewsbury:




    Overhead supply or LPS fitted



    I can see the sense of that, but I can only see the LPS bit mentioned in BS 7671 (534.4.1.3) - is the overhead line bit mentioned somewhere else in BS 7671 or is that just accepted good practice that has escaped our regs?

      - Andy.

     




    534.4.1.3 (cryptically).


    Only general good-practice guidance to be honest ... overhead lines (including LV) are not unknown to suffer direct strike, and therefore "or protection against the effects of direct lightning" may well apply.

    I guess it depends on the length of overhead supply, and what other higher structures are around, in reality.

  • 0

    534.4.1.3 (cryptically).


    ... overhead lines (including LV) are not unknown to suffer direct strike, and therefore "or protection against the effects of direct lightning" may well apply.



    I did wonder about that, but I ended up reading it as:


    "and the structure is equipped with ... protection against the effect of direct lightning..."


    i.e. the structure has some kind of system to protect it against lightning that isn't strictly an 'external lightning protection system' (not sure what that might be - maybe a steel structure that acts as its own lighting rod?).

    So I read it as when the structure has protection, rather than when it's in need of protection.


    Cryptic indeed! It does seems sensible though.


       - Andy.

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