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Anonymous Poster #1

Advanced Lightning Protection System

02/27/2017 4:09 AM

Hi,

How 80 metre of radius is established? The following is an excerpt from a BoQ.

80 m at level 3, Protection radius Rp(m) = 80 meter Early Streamer Emission Lightning tip (stainless steel 470x60/590x120) , Mast for Lightning Arrestor, 75 sq. mm copper strip bar without any joint in middle of the span from Lightning tip to separate Earth Station.

Regards,

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#1

Re: Advanced Lightning Protection System

02/27/2017 1:34 PM

This helpful guide will help explain things and offer solutions.

Dehn Lightning Protection Guide

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#2
In reply to #1

Re: Advanced Lightning Protection System

02/28/2017 8:24 AM

At 80M, you're into the rolling sphere 160M in diameter, running around on the ground

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Anonymous Poster #1
#3
In reply to #2

Re: Advanced Lightning Protection System

03/28/2017 9:18 PM

how is this diameter of 160 m running around the ground? How is the boundary of protection defined?

Regards,

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#4
In reply to #3

Re: Advanced Lightning Protection System

03/28/2017 11:10 PM

See the link in post #1 for an explanation (with pictures).

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#5
In reply to #3

Re: Advanced Lightning Protection System

03/29/2017 10:57 AM

Lightning can strike with equal probability anywhere on the surface of this sphere, where the surface touches some object.

So if your 160M sphere touches only earth, clear all around, the highest probability is that the lightning will go to earth. If some object above the ground touches the surface of the sphere, wherever you put it, lightning has equal probability of striking that object or ground.

If some object is below the higher object above, then it has a lower probability of being struck by lightning, so the upper object is a shield for the lower object.

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Anonymous Poster #1
#6
In reply to #5

Re: Advanced Lightning Protection System

05/04/2017 6:43 AM

Dear Sir,

In my case, there is one central building and there are other buildings around it.

For example, we have a 160 metre radius sphere.

For analysis, if this sphere is placed in one side, the sphere may touch the other building as well. In this case, the area covering the sphere will be protected.

But again if the sphere is placed in other side, it may touch other building roof. And again the sphere will be protected.

But the lightning pattern is unknown. Can we say that all the buildings surrounding the central building is protected if it is within 160 metres radius?

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#7
In reply to #6

Re: Advanced Lightning Protection System

05/04/2017 2:02 PM

The sphere is where the lightning will strike, protected is outside the sphere.

If you roll the sphere around on the ground, whatever touches the surface (including the ground) is equally likely to get a direct strike. So the small triangular area to either side of the sphere (in 2 dimensions) is a protected zone, when the surface of the sphere is placed to touch a building and the ground.

The pieces that are not included in the sphere, completely outside the sphere, no matter where you put it, then those pieces are protected (shielded) by the thing that touches the surface of the sphere first.

Not so easy to describe in words, especially translated, maybe easier to build a crude 3D model from boxes, and use a convenient ball to see what is protected?

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#8
In reply to #6

Re: Advanced Lightning Protection System

05/04/2017 3:53 PM

Please view the link in post #1 for the answer.

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#9
In reply to #8

Re: Advanced Lightning Protection System

05/04/2017 4:48 PM

Page 63 might be helpful as illustration

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