×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

lightneing arrestors

lightneing arrestors

lightneing arrestors

(OP)
On high rise buildings and towers, we put lightning arrestors. Can any one give me the guide lines with figures and formulas, on number of arrestors to be put in existing factory premises ? Are there rules which specify how much area one arrestor will cover ? Are there guide lines for earth resistance for such arrestors ?



  

RE: lightneing arrestors

Suggestion: It is more appropriate to refer to lightning rods or air terminals.
One good source is NFPA 780
Visit
http://www.nfpa.org
for more info.
This approach is based on Faraday Cage principle.
Usually, it is applied to a large footprint low height structure.
Early Streamer Emission principle is based on
Franklin Cone principle
Usually, it is applied to a small footprint high structure.
Visit
http://hearybros.com/english/index2.html
etc. for more info

RE: lightneing arrestors

If you are not in North America, you may find the IEC standad would be applicable in your region.  The document is IEC 61024 (series) 'Protection of Structures against lightning'.  There are a couple of parts to this standard that collectively covers the risk assesment of structures. to the selection and placement of air-terminations.

As far the resistance to ground goes, 10 Ohms is the target resistance of the lightning earthing system.

The most effective stake design that I have seen is a shallow rod electrode (3m) with short (400mm) horizontal feeders radiating from the bottom (like an inverted propeller).

RE: lightneing arrestors


chiplonkar, you refer to “lightning arrestors” but do you mean “air terminals”?
  

RE: lightneing arrestors

Hi chiplonkar,

Your requirement merely depends on the fact that how much your building is exposed to direct lightning strikes. In other words before you invest on a typical ligtning proetction system you have to do a risk analysis. For that you need to follow the methodology specified in detail in BS 6651 ( IEC 61024 does not specify any methodology )and conclude how much is your risk factor. Then you can specify how many air terminations and down comers you need.Also it specifies how much resistance you have to have for an individual electrode and when all the electrodes are connected as grid etc.

In addition you have to consider other design aspects with regard to indirect lightning strikes such as coupling etc.

NFPA 780 too covers the subject very widely which is used in ANSI world. But I personally feel BS 6651 is better which is widely used in the IEC world.

Regards!

Kiribanda

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources