Lightning Connection

i can't give you any specs, but common sense should tell you that lightening will travel the path of least resistance.there's no need to run it through conduit. ithink you should run it to a pair of ground rods.

Whether lightning conductor or service connection to a building, if passed through a metal pipe some energy will be dissipated by eddy current heating,before reaching the connected equipment

Is the lightning rod conductor turning 90 degrees as it appears in the photo?

If so I would see that as a higher impedance(inductance) to a lightning discharge than it running through a conduit.

My understanding is that a lightning arrestor conductor should follow the shortest. most direct path to earth with the minimum number of gentle bends possible.

I expect there to be standards to this effect but I do not have our local ones to hand and there will be subtle differences from region to region, therefore check your local regulations.

Yes it turns 90° but with more than 8" radius. The standard I mentioned says that you should not run the down conductor through a pipe like this, acording to what an expert told me, bue I don´t have this spec to show it to my client.

Thanks WAWAUS!

If a service conductor(phase and neutral) runs through a metal pipe and if a surge travels along that cable towards the premises,some destructive energy in the surge could be dissipated as heat in the pipe before it reaches the terminal equipment/load centre..

You might consider this a guard of sorts for the down conductor. As lightning is very unpredictable and of greatly varying energy levels, it is hard to say precisely what it will do. In any case, if you electrically make an NFPA 780-compliant bond from conductor to the top and bottom of the conduit, it will basically become a minor part of the conductor. Review the text from 780 that may allow this-it is articles 4.9.11 and 4.9.11.1.

You would not catch me anywhere near that downpipe, anymore than I would have a hand on the conductor......

In high voltage situation, assuming the concrete tube is not a perfect conductor(?!?), then you have just built a big capacitor.......that tube might even start to melt when lightning strikes.....

To sum up my thoughts, the tube is just a waste of time and money..... I see no plus points.

Right...not normally used. We just run a bare wire separated from the structure with insulators.

Same here.....

http://www.lightningsafety.com/nlsi_lhm/lpts.html

From many years as a power protection / lightning protection contractor I can tell you the conduit is the least of your problems & forget the engineering soloutions / standards but consider these points.

1/ The energy dissipated in the average direct hit lightning strike ??

2/ The current carrying capacity of the conductor used ??

3/ The insulation value of your average block of steel reinforced concrete ??

4/ The reaction of concrete to extream heat ??

5/ Minimum bending radius of HV cables, and its effect on the insulation resistance.

The result of a hit on that system would be a vapourised conductor, a large hole in the concrete where the energy broke the concrete insulation barrier on its way to the closest grounded point IE the reo bar in the structure and a shower of concrete shrapnell from the explosion resulting from the heating effect on the concrete.

I cant see the conduit being a problem....

Thanks

Please see post #14 which is the standard reference in question.

IEEE 124 1991 2.2.6

I believe you mean IEEE Std 142-1991 2.2.6, which states:

"2.2.6 Bonding of Metal Sleeves Enclosing a Grounding Conductor. The behavior pattern of an independent grounding conductor (such as the run to the grounding electrode at the service or the grounding conductor connecting a surge arrestor to an earthing terminal) is very different from that of a power circuit grounding conductor.

"...There will be an inductive voltage drop along the conductor length due to a changing current...The larger the conductor diameter, the lower will be the conductor inductance (or reactance). If the member enclosing the conductor is magnetic, the magnetic field encircling the conductor is increased, which correspondingly increases the inductive voltage drop. If the enclosure is plastic conduit, there will not be a magnetic effect...although even aluminum has an effect from eddy current generated in the conduit. It has been found that enclosing a single grounding conductor in steel conduit increases its impedance by a factor of up to 40.

"In some cases, installation conditions are such as to warrant the application of a metal enclosure over a section of this type of grounding conductor. In all cases where this is done, the conductor and the enclosing protective metal shell should be bonded together at both ends of the every integral section of enclosure for the following reasons:

(1) To avoid increased voltage drop if the enclosure is made of magnetic material.

(2) To take advantage of the lower voltage drop associated with larger conductor diameter

(3) To permit the steel conduit to carry the major portion of the ground seeking current."

(emphasis added)

Therefore, in my opinion as per the intention of the IEEE, the aluminum conduit should be bonded as a steel "magnetic" conduit should be even though the reactance will be at a lower level (it still exists) to improve the health of the lightning protection system and avoid heating and arcing events from lightning strokes.

Rigth, this is what I was looking, thanks Cuba_pete, I already got the 2001 version and. Thnak you very much