Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 32 replies
  • Subscribers 32 subscribers
  • Views 2628 views
  • Users 0 members are here
Options
You may also be interested in
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

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


Parents
  • 0

    psychicwarrior:




    gkenyon:




    psychicwarrior:

    Forgive me to come back to this again, but...


    Take a *row* of small shops in a town centre all joined together, just for instance.  e.g. Urban, commercial and no LPS on the row.


    Reading the Regs, it is mentioned that SPDs are for transients from atmospheric and from switching - but it details that concern is for switching from *within* the installation only, as I read it.


    Therefore if the example shop is not concerned with internal switching i.e. it only has a till and some lights, then the concern is only with atmospheric.


    Given a shop is a commercial activity, a risk assessment approach cannot be taken and Regs state fit a SPD; as an aside, this applies it seems, even if it is a shop selling junk and a shop floor the size of a six-pence and a domestic probably has more 'value' in it. Given there is no LPS on the shop (or the row of), then its a TYPE 2 SPD near the origin (well, in the shop DB).   Correct please ?

    oh and  only when an LPS is fitted is a TYPE 1  required too (or a 1+2).  ?


    Regards

    Habs




    All of these questions are answered in sections 3.7.2 and 3.7.3 of the OSG (pp39-41 of the current edition).


     




    My good man, with respect I say, as are a lot of questions raised on here covered/answered in the usual and other publications !


    I am sorry my question caused that big sigh from you :-)    I do read before I ask anything...perhaps that just makes it worse  haha


    A simple brief yes, no discussion perhaps just to see if I understood what I read.


     




    Apologies if you took that the wrong way.


    The answer then is not fully.



    Take a *row* of small shops in a town centre all joined together, just for instance.  e.g. Urban, commercial and no LPS on the row.


    Reading the Regs, it is mentioned that SPDs are for transients from atmospheric and from switching - but it details that concern is for switching from *within* the installation only, as I read it.


    Therefore if the example shop is not concerned with internal switching i.e. it only has a till and some lights, then the concern is only with atmospheric.





    Yes, I'm with that.



    Given a shop is a commercial activity, a risk assessment approach cannot be taken and Regs state fit a SPD; as an aside, this applies it seems, even if it is a shop selling junk and a shop floor the size of a six-pence and a domestic probably has more 'value' in it.



    No. This depends on what's going on in the shop.


    So, the commercial activity of the junk shop you describe is unlikely to be affected by a surge event, and the business can probably continue using cash and hand-written receipts. However, the following kinds of shop are a different situation:


    • Supermarkets, butchers and similar with high value of products in refrigerators and freezers

    • Jeweller or antique shop with expensive security systems

    • Businesses that rely heavily on electronic transactions


    Given there is no LPS on the shop (or the row of), then its a TYPE 2 SPD near the origin (well, in the shop DB).   Correct please ?

    oh and  only when an LPS is fitted is a TYPE 1  required too (or a 1+2).  ?



    I think the simplest approaches to consider are:

    Small installation (only DBOs at the origin)


    • Overhead supply or LPS fitted: Combined Type 1 & Type 2 at the origin. Type 3 only necessary at very sensitive equipment where manufacturer recommends it.

    • Otherwise, Type 2 at the origin. Type 3 only necessary at very sensitive equipment where manufacturer recommends it.

    Installation with main board and sub-boards


    • Overhead supply or LPS fitted: Type 1 at the origin and Type 2's at sub-boards. Type 3 only necessary at very sensitive equipment where manufacturer recommends it.

    • Type 2 at the origin. Type 3 only necessary at final boards and/or very sensitive equipment where manufacturer recommends it.


    For all installations, if SPDs are required for the mains, they should also be considered for external metallic telecomms services (not fibre), and vice-versa. Regulation 443.1.1 points you to the relevant standards for this.

    If you send cables outside the building ("Zone") then they may also require surge protection.
Reply
  • 0

    psychicwarrior:




    gkenyon:




    psychicwarrior:

    Forgive me to come back to this again, but...


    Take a *row* of small shops in a town centre all joined together, just for instance.  e.g. Urban, commercial and no LPS on the row.


    Reading the Regs, it is mentioned that SPDs are for transients from atmospheric and from switching - but it details that concern is for switching from *within* the installation only, as I read it.


    Therefore if the example shop is not concerned with internal switching i.e. it only has a till and some lights, then the concern is only with atmospheric.


    Given a shop is a commercial activity, a risk assessment approach cannot be taken and Regs state fit a SPD; as an aside, this applies it seems, even if it is a shop selling junk and a shop floor the size of a six-pence and a domestic probably has more 'value' in it. Given there is no LPS on the shop (or the row of), then its a TYPE 2 SPD near the origin (well, in the shop DB).   Correct please ?

    oh and  only when an LPS is fitted is a TYPE 1  required too (or a 1+2).  ?


    Regards

    Habs




    All of these questions are answered in sections 3.7.2 and 3.7.3 of the OSG (pp39-41 of the current edition).


     




    My good man, with respect I say, as are a lot of questions raised on here covered/answered in the usual and other publications !


    I am sorry my question caused that big sigh from you :-)    I do read before I ask anything...perhaps that just makes it worse  haha


    A simple brief yes, no discussion perhaps just to see if I understood what I read.


     




    Apologies if you took that the wrong way.


    The answer then is not fully.



    Take a *row* of small shops in a town centre all joined together, just for instance.  e.g. Urban, commercial and no LPS on the row.


    Reading the Regs, it is mentioned that SPDs are for transients from atmospheric and from switching - but it details that concern is for switching from *within* the installation only, as I read it.


    Therefore if the example shop is not concerned with internal switching i.e. it only has a till and some lights, then the concern is only with atmospheric.





    Yes, I'm with that.



    Given a shop is a commercial activity, a risk assessment approach cannot be taken and Regs state fit a SPD; as an aside, this applies it seems, even if it is a shop selling junk and a shop floor the size of a six-pence and a domestic probably has more 'value' in it.



    No. This depends on what's going on in the shop.


    So, the commercial activity of the junk shop you describe is unlikely to be affected by a surge event, and the business can probably continue using cash and hand-written receipts. However, the following kinds of shop are a different situation:


    • Supermarkets, butchers and similar with high value of products in refrigerators and freezers

    • Jeweller or antique shop with expensive security systems

    • Businesses that rely heavily on electronic transactions


    Given there is no LPS on the shop (or the row of), then its a TYPE 2 SPD near the origin (well, in the shop DB).   Correct please ?

    oh and  only when an LPS is fitted is a TYPE 1  required too (or a 1+2).  ?



    I think the simplest approaches to consider are:

    Small installation (only DBOs at the origin)


    • Overhead supply or LPS fitted: Combined Type 1 & Type 2 at the origin. Type 3 only necessary at very sensitive equipment where manufacturer recommends it.

    • Otherwise, Type 2 at the origin. Type 3 only necessary at very sensitive equipment where manufacturer recommends it.

    Installation with main board and sub-boards


    • Overhead supply or LPS fitted: Type 1 at the origin and Type 2's at sub-boards. Type 3 only necessary at very sensitive equipment where manufacturer recommends it.

    • Type 2 at the origin. Type 3 only necessary at final boards and/or very sensitive equipment where manufacturer recommends it.


    For all installations, if SPDs are required for the mains, they should also be considered for external metallic telecomms services (not fibre), and vice-versa. Regulation 443.1.1 points you to the relevant standards for this.

    If you send cables outside the building ("Zone") then they may also require surge protection.
Children
No Data

Community Rules & Guidelines