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SDP for a DB feeding external loads

Apostolos

Good morning

I think this question, or similar ones, may come back again and again.

We have a building with Faraday cage lightning protection

So in the Main Distribution Panel we have included a T1+2 surge protection

Couple of floors up, we have a mechanical DB feeding condenser units that are exposed in the roof.

We also have an external services DB that is feeding external lighting (columns, bollards etc)

Now, I know that usually the sub DBs are being protected by T2 only SPD.

However I am reading that T1 is about direct lightning strike and I am wondering wether for these 2 DBs only I should use a T1+2 assuming that both the condensers on the roof or the lighting columns may be subject to a direct strike

I really would like your opinion on this.

Should I stick to a T2 or go to a T1+2 based on my train of thought above?

Thanks!

Parents

  • Not my area of expertise at all, but a few questions come to mind (might help get the discussion going too)

    Does the outside lighting involve overhead lines - or more like buried SWA cables feeding steel columns/bollards? If the latter I wonder if they form a kind of sausage shaped earthed shield/cage extension that surrounds the live conductors externally?

    Would the units on the roof be expected to receive direct lightning strikes - or would they be protected by the LPS? I gather that air rods provide protection to some distance horizontally/vertically below (either a cone of protection or such that a theoretical rolling sphere of a certain size couldn't touch the units without encountering an air rod).

       - Andy.

Reply

  • Not my area of expertise at all, but a few questions come to mind (might help get the discussion going too)

    Does the outside lighting involve overhead lines - or more like buried SWA cables feeding steel columns/bollards? If the latter I wonder if they form a kind of sausage shaped earthed shield/cage extension that surrounds the live conductors externally?

    Would the units on the roof be expected to receive direct lightning strikes - or would they be protected by the LPS? I gather that air rods provide protection to some distance horizontally/vertically below (either a cone of protection or such that a theoretical rolling sphere of a certain size couldn't touch the units without encountering an air rod).

       - Andy.

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