Lightning Protection - IS 2309

Using Onderdonk's formula and plugging in your wire material and circular mils you can find out how fast this wire will melt with the current going through it. 16 gauge copper wire: Tmelt = 1083, Area = 2581 circ mil, Time = 5 sec,diam = .0524 inches, Tamb = 25 E= Area in CM, B = Tmelt - Tamb in deg. C, D = 234-Tambient in deg. C, T= time in seconds., So, E = 2581, B= 1058, D=209, T=5, Then, Ifuse = E* SQRT {<LOG[(B/D)+1]>/(T*33)}, Ifuse = 2581* SQRT {<LOG[(1058/210)+1]>/165}, Ifuse = 2581* SQRT {<LOG(6.04)>/165}, Ifuse = 2581* SQRT {0.781/165}, Ifuse = 2581* SQRT {.00473}, Ifuse = 2581* 0.0688, Ifuse = 178A

Hi,

The USA standard NFPA-780-2008 states that the minimum size for Class 2 (industrial) wiring for Copper is 59 mmsq (8.6mm diameter) and 97 mmsq (11.1mm diameter) for Aluminum. Therefore,conductor material is important in your choice as well as size.

There is a European Norm standard that could help in you determining the conductor size.

EN 50164-2: 2002 - Lightning protection components (LPC)

Part 2: Requirements for conductors and earth
electrodes. This standard describes, for example, dimensions and tolerances for metal conductors and earth electrodes as well as the test requirements to the electrical and mechanical values the materials.

You also may want to reference the IEC 62305 series of standards for Lightning Protection. This standard series is an excellent set of documents pertaining to lightning protection.

For further information, you can go to the following web site:

Dehn Lightning Protection Guide

This site is the chapters to a book that gives detailed information about designing lightning protection systems and even application notes for specific installations such as wind power, photovoltaics, bio-gas, cell towers, farms, etc...

I hope all of this helps.

keep well.

Hello, my question is on reference the lightning conductors (down conductor), I'm working in a project where exist a 100 ft telecom tower, the specificaction client require a 600 V, thw-ls insulation, but checking the NFPA 780-2008, the conductor is class II, 115 kcm Cross section area and obviusly uninsulated, I had spoke with the design engineer (telecom specialist) and he saw that is frecuently used on telecom towers install this type of conductor, but I understand that is wrong, and I want avoid install wrong materials.

Can you tell me if exist some normative reference for down conductors on telecom towers that indicate the need of install insulated conductor?

Thanks

8.6 mm = 0.34" dia.

Using the Preece equation for fusing current, with 10244 for copper = 10244(0.34"^1.5) = ~2000 Amps