Lightning Protection

[Ally Kanyondo]

Dear All,

 

I need briefly explanation about the lightning protection in high rise building and in churches with reference to the following.

 

1.What are the good position to install lightning arrestors in tall buildings

2. There is the maximum radius in which the lightning arrestor can protect, i need the formula on how to calculate that radius or area

 

I m expecting to get a good explanations from my fellow engineers.

 

Kind regards

[admin]

[admin]

Hello,

 

You should look for you answers in IEC 62305 2nd edition, parts 1 (for an introduction) & 3 (for detailed explanation).

Another source of info is the DEHN lightning protection guide which can be freely downloaded from their website.

[admin]

NFPA 780 would be another good start for informaton.

[admin]

I think you need to be a little clearer in what you are asking and trying to achieve.

Are you trying to place lightning dods on the highest points of the building to attract lightning to set locations from which you then provide heavy conductor connections directly to earth so that you control the path of lightning currents rather than allowing them to pass anywhere they like through the building structure. This is lightning protection and is protection for the structure. It is suaually accomplished using air terminals on the highest part of the building with one or more down conductor connections into a buried earth grid. You can get some guidance on the coverage of air terminals from standards such as AS1768 or equivalent other British, intenational or American standards. It may also be worth talking to lightning protection experts such as Erico as there are many types of lightning conductors, other than simple rods, which provide improved areas of coverage.

or

Are you trying to connect lightning devices to electrical systems which may have components outdorrs and subject to lightning strike in order to conduct the high impulse voltage to ground to pretect internal electrical equipment from the excessive voltage spike. This is lightning arresting.

[Ally Kanyondo]

Smithy said:

I think you need to be a little clearer in what you are asking and trying to achieve.

Are you trying to place lightning dods on the highest points of the building to attract lightning to set locations from which you then provide heavy conductor connections directly to earth so that you control the path of lightning currents rather than allowing them to pass anywhere they like through the building structure. This is lightning protection and is protection for the structure. It is suaually accomplished using air terminals on the highest part of the building with one or more down conductor connections into a buried earth grid. You can get some guidance on the coverage of air terminals from standards such as AS1768 or equivalent other British, intenational or American standards. It may also be worth talking to lightning protection experts such as Erico as there are many types of lightning conductors, other than simple rods, which provide improved areas of coverage.

or

Are you trying to connect lightning devices to electrical systems which may have components outdorrs and subject to lightning strike in order to conduct the high impulse voltage to ground to pretect internal electrical equipment from the excessive voltage spike. This is lightning arresting.

---

Dear Smithy

Thanx for the clarification, my problem is about lightning protection as the heading states. I know it is accomplished by using air terminals.

My problem is to know if there is a formula to calculate the maximum area one air teminal should cover, Assume the building has four point of the same level of which i can put air terminal, should i put air terminal in all points i must make some calculations to know how many i should connect.

Also give me the way i should contact this expert ERICO.

Regards

[admin]

Hi,

The formula for the lightning protection, Franklim pole type:

Rp=h*tan A

Where Rp is the radius of protection of a cone defined by the formula, with the height h in meters (h is the top point of the pole) and A is the angle in degrees at the top, that usually is 55º for a class IV degree of protection.

For an electronic protection pole, the formula is rader complicated, and for that you should contact the manufacters because they have tables for each equipment.

 

Best Regards,

Adriano

[IHOORA MICHAEL]

My regards;

   The number of down
conductors can be determined as follows:

1-One conductor for a structure whose base area does not
exceed100 sq m

 

2-Determine the whole numbers N1 and N2, and select the
smaller of the two

       
N1=1+(A-100)/300

 

        N2=P/30

 

  Where N=whole number
of the working area

              A=base
area of the structure in sq m

             
P=perimeter of the structure in m

 

3-Where the height of the structure is more than 30m in
height, additional considerations             to
the above should be applied.

[admin]

The lightning arrestor will be inthe midlle

Q²=L²+W²

 L=Roof  long demention

W= Roof waid demention

h= hight of lightning arrestor

Z= buildind hight

if Z<30m ……….h=0.5Q+1

IfZ >30m ………h=(3/5)Q

[admin]

You can try “ionisation”  type lightning conductors. Usualy you can download the dimensioning software from the manufacturers website/

http://www.indelec.com

http://www.erico.com

http://www.at3w.com

[Author]

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