Construction activity and the Code

[gadfly56]

First let us see whether we agree with the theory or not (Post no.47).State what the flaws are in it apart from practical implementation.

If you had an actual theory or hypothesis AND some data to back it up we might be able to get somewhere. The burden of proof is on the person asserting it can be done. And, after all, "practical implementation" is what it's all about in the end. Come back with some answers to my questions (conductor size, length) and we might be able to move forward.

You want to bond the bucket. Fine. We have one post where a #6 ground wire was vaporized by a lightning strike. Well, THAT didn't work. The ball is in your court.

 

[T.M.Haja Sahib]

You want to bond the bucket. Fine. We have one post where a #6 ground wire was vaporized by a lightning strike. Well, THAT didn't work. The ball is in your court.

But that was a single conductor taking full lightning current.But if the bucket of the lift could be suitably bonded, without affecting its functionality, to the building steel,it would not happen.

 

[gadfly56]

But that was a single conductor taking full lightning current.But if the bucket of the lift could be suitably bonded, without affecting its functionality, to the building steel,it would not happen.

Again, you side-step the discussion. What, exactly, is "suitable"? How many conductors? What size? What length? Bonded where on the bucket? Bonded where on the steel? Method of bonding? Is there any empirical data to support your methodology? Define the bucket's functionality, and describe how your bonding proposal would NOT adversely affect the functionality. After we get through ALL of the above, NOW we can discuss your claim that proper bonding could prevent a future occurance of this incident.

 

[iMuse97]

But my conviction is not based on gut feeling! Go back to the post no.39.Even though the tower of the lift is reliably grounded and bonded to the building steel.The metal bucket of the lift is not:The lightning current had to travel round from the bucket,along the lift rope to the building steel.Instead,the lightning side flashed to the building steel bypassing the above path.So the metal bucket of the lift should be PROPERLY bonded to the building steel as soon as it arrives at the designated location near the building structure.Now the side flash hazard eliminated, the workers may handle the bucket with suitably insulated gloves and boots.

All this is is gut feeling and conviction with no basis in fact.

Side-flash (btw, lightning doesn't care which way it flashes) or any other flash hazard is not eliminated, and no worker will be safe with unless their suitably insulated workwear keeps them more than 100 meters from the blast created by the flash. As Gadfly just mentioned, the heart of the matter is that there is no such thing as suitable when even a "side-flash" (to use the terminology mentioned) cannot be controlled and channeled effectively into any single bonded system.

 

[iMuse97]

But that was a single conductor taking full lightning current.But if the bucket of the lift could be suitably bonded, without affecting its functionality, to the building steel,it would not happen.

I humbly submit that we have no idea whether that was "full lightning current" or just a small portion of whatever the full lightning current/voltage was.

 

[T.M.Haja Sahib]

Again, you side-step the discussion. What, exactly, is "suitable"? How many conductors? What size? What length? Bonded where on the bucket? Bonded where on the steel? Method of bonding? Is there any empirical data to support your methodology? Define the bucket's functionality, and describe how your bonding proposal would NOT adversely affect the functionality. After we get through ALL of the above, NOW we can discuss your claim that proper bonding could prevent a future occurance of this incident.

We have to agree on to something.Otherwise continuing this thread is meaningless.Have a look at posts nos.31,32,33 &42.Do you agree that the bucket of the lift could be bonded per NFPA780 even though it does not explicitly mention about a bucket lift?

 

[jumper]

We have to agree on to something.

Not on this forum, Sahib. Most of us are stubborn as mules.

I know nothing about lightning, but this thread is really interesting.:thumbsup:

 

[T.M.Haja Sahib]

All this is is gut feeling and conviction with no basis in fact.

Side-flash (btw, lightning doesn't care which way it flashes) or any other flash hazard is not eliminated, and no worker will be safe with unless their suitably insulated workwear keeps them more than 100 meters from the blast created by the flash. As Gadfly just mentioned, the heart of the matter is that there is no such thing as suitable when even a "side-flash" (to use the terminology mentioned) cannot be controlled and channeled effectively into any single bonded system.

Do you not believe that a lightning protection method devised per NFPA 780 offers a high degree of protection against such hazards?

We are discussing about a lightning incident that happened.Refer back to the news paper report on post no.1.There is no mention of 'throwing away of workers 'by the lightning strike;only mention of workers taking the hit.That means there was no blast force exerted by the subject lightning on the workers.This ,combined with the absence of any statistics on number of people injured/killed by blast of lightning arc ,makes the discussion of lightning arc blast irrelevant as far as the subject lightning incident is concerned.

 

[T.M.Haja Sahib]

I humbly submit that we have no idea whether that was "full lightning current" or just a small portion of whatever the full lightning current/voltage was.

Okay.This may make it clear.''That was a single conductor not sized in accordance with NFPA 780 taking a direct hit from lightning.''

 

[iMuse97]

Do you not believe that a lightning protection method devised per NFPA 780 offers a high degree of protection against such hazards?

We are discussing about a lightning incident that happened.Refer back to the news paper report on post no.1.There is no mention of 'throwing away of workers 'by the lightning strike;only mention of workers taking the hit.That means there was no blast force exerted by the subject lightning on the workers.This ,combined with the absence of any statistics on number of people injured/killed by blast of lightning arc ,makes the discussion of lightning arc blast irrelevant as far as the subject lightning incident is concerned.

As to your point about the blast. Point made; point taken.

And no: in construction settings, I wouldn't give the NFPA 780 a second thought. I really don't think that I could entrust my personal safety or those of people working for me to the theoretical lightning protections that could at any time be overruled by actual lightning.

As to the possibility that these NFPA 780 protection methods could offer some degree of protection: sure, I grant that.

Do I think that such protection methods could offer a high degree of protection in a construction setting? No.

The only method to work safely in an electrical storm: Stop and have a cup of coffee.

 

[T.M.Haja Sahib]

Not on this forum, Sahib. Most of us are stubborn as mules.

Including me.:lol:

 

[hurk27]

Okay.This may make it clear.''That was a single conductor not sized in accordance with NFPA 780 taking a direct hit from lightning.''

Ok I have stayed quite on this thread for a while to kind of see which way it would go, and I see that we have an argument without proper knowledge in the subject of lightning science, As kind of pointed out a few things in post 22 lightning does not follow the fundamentals of what many of us here understand in electrical theory, it is a science in its own realm, here is the one main thing that most do not understand and that I also pointed out in post 22, lightning has a high frequency component, it has a fast rise time and decay and will in all strikes cause oscillations even before the the lightning hits its target, this many times can steer the lightning as to what it is going to be hit at that time, while this effect is not yet fully understood but if you have any training into how radio waves work and how an antenna has to be close to the resonating frequency of the signal before the electrons can build up on it, then you can understand how lightning can see a 15' tall tree with branches of many different lengths (broad band antenna) and not even attempt to strike a well grounded 300' tower not more then 50' away.

This theory is also the bases why we see lightning take strange paths that just don't make sense to the average electrician, but if you can understand that when you apply radio theory it becomes clearer, I have seen lightning follow some of the most backwards paths that one would think if it was trying to go to straight Earth, in one case it struck a phone trunk line and instead of going to a service it was bonded to, that not only had two ground rods and a city water pipe that ran for miles underground, (this I know for fact our water lines are not isolated) it followed a small 2 pair 28awg phone wire outside over 60' to the other side of the house where it can close enough to a chain link fence where it arced off to and never damaged anything but the phones in the house, the small phone wire was vaporized up to the fence but after that was totally intact and usable, this is just one of the many strikes I have been on over the years.

Growing up in Florida was why lightning was such an interest to me, I was following storms all across Florida, spent many hours camped out about a mile of some very tall TV towers, one was over 1700' just north of Orlando, Fl. I have seen the damage of what was once called "super lightning" (positive stroke) can cause, I did a 3 year intern at the University of Florida before Camp Blanding was being used for regular rocket launches by them and others, I have done some of my own experiments with towers and setting up many towers and grounded them using many different methods, and using old Hawk Eye flash lamps to set up a way to know when which tower received a strike, the strange thing (was back then) I learned was even with all these grounded towers in this field, lightning would hit the trees more then anything else, and after I learned the reason why (as I posted above) it all started to make sense.

Am I an expert in lightning? far from it, I never got the chance to carry out the many experiments that would be required to bring all these theory's into the realm of a fact, but I do believe I have a good understanding at some of the things it does and why, at least enough to know what is a myth or not, and this is still one of the areas that keeps coming back is old myths that get many to believe something that which is not a fact.

The one fact that there has been papers written on, is that lightning is a high frequency event but it is also a variable and depending upon many factors can vary as low as 20hz to over 1 Ghz but most frequently is centered around 1Mhz but it is not un common to find low cloud lightning at 10 Mhz, and if you can start to calculate the impedance and wave length of conductors with these frequencies in mind, you will start to draw a picture of how little effect grounding can be, a given wire at a given length can have a resonating wave length and impedance if the frequency is known, but this is the problem! We just don't know what the frequency is going to be, and this is why it will always be a hit and miss, which is why my statement in the last sentence of post 22

 

[T.M.Haja Sahib]

Do you not believe that a lightning protection method devised per NFPA 780 offers a high degree of protection against such hazards?

We are discussing about a lightning incident that happened.Refer back to the news paper report on post no.1.There is no mention of 'throwing away of workers 'by the lightning strike;only mention of workers taking the hit.That means there was no blast force exerted by the subject lightning on the workers.This ,combined with the absence of any statistics on number of people injured/killed by blast of lightning arc ,makes the discussion of lightning arc blast irrelevant as far as the subject lightning incident is concerned.

As to your point about the blast. Point made; point taken.

And no: in construction settings, I wouldn't give the NFPA 780 a second thought. I really don't think that I could entrust my personal safety or those of people working for me to the theoretical lightning protections that could at any time be overruled by actual lightning.

As to the possibility that these NFPA 780 protection methods could offer some degree of protection: sure, I grant that.

Do I think that such protection methods could offer a high degree of protection in a construction setting? No.

The only method to work safely in an electrical storm: Stop and have a cup of coffee.

It is known that lightning can still strike without the warning of a thunderstorm.In such rare cases adopting NFPA 780 and points mentioned in this thread against the subject lightning strike may help during the construction activity in open .

 

[hurk27]

There's one other item I would like to bring out.

EMP!!! "Electromagnetic Pulse”

While many of us are very familiar with the term NEMP or "Nuclear Electromagnetic Pulse” from movies, and it is a fact of life, but only a few understand that lightning also creates this same pulse just many times weaker, and if you want to look it up its called LEMP or "Lightning Electromagnetic Pulse”

The reason I bring this up is this pulse is what causes more electronics damage then the actual lightning, sure direct strikes can cause a catastrophe of physical damage, but many strikes are not direct, in fact it is starting to be believed more and more that near field strikes are the major cause and more frequent as we are running into more electronic damage then we see physical damage, in a near field strike this EMP will induce current into any wiring that is in a loop just like a transformer, but at a very high frequency, this may set up circulating currents in a run of cable such as NM and interconnected equipment such as networks, TV cable, phones, and even audio components of a home theater system like the audio cable running between a amplified sub and the main system, the bad thing is that this pulse will use all the conductors of a cable as one wire, this completely by passes any TVSS protection that this equipment might have (how many seen equipment damage while plugged in to a surge strip while other equipment plugged in to that same strip had none?) If you would have been looking you would have seen equipment with other pathways such as phones or TV's and yet a stand alone computer or laptop with wire less networking wasn't damaged, this is a very good sign of a near field EMP strike, maybe to a tree out in the yard up to 200' away.

Now protecting from these LEMP's can be very hard to accomplish after the building is built, sure there are things that can be done after the fact but will not be as effective as designing from the beginning, most of what was learned by the military to block NEMP's applies to lighting EMP's but if you ever get into this field you can see how over whelming it can be, a HF EMP can get through the smallest crack on the shielding and the open Faraday cage in a previous post would not shield from this also.

Edited to add one other thing, this "induced" current like in a transformer secondaries, it no longer has reference to Earth, nor is it trying to return to Earth it only tries to complete a path within the affected circuit loop it has been induced into.

 

[T.M.Haja Sahib]

Ok I have stayed quite on this thread for a while to kind of see which way it would go, and I see that we have an argument without proper knowledge in the subject of lightning science, As kind of pointed out a few things in post 22 lightning does not follow the fundamentals of what many of us here understand in electrical theory, it is a science in its own realm, here is the one main thing that most do not understand and that I also pointed out in post 22, lightning has a high frequency component, it has a fast rise time and decay and will in all strikes cause oscillations even before the the lightning hits its target, this many times can steer the lightning as to what it is going to be hit at that time, while this effect is not yet fully understood but if you have any training into how radio waves work and how an antenna has to be close to the resonating frequency of the signal before the electrons can build up on it, then you can understand how lightning can see a 15' tall tree with branches of many different lengths (broad band antenna) and not even attempt to strike a well grounded 300' tower not more then 50' away.

There is one problem:the 15' tall tree with branches of many different lengths acted as a broad band antenna to attract the lightning with a spectrum of frequency.If it were tuned to a single frequency,the lightning would have missed it.But still, many other objects around the tree could also be tuned to the same spectrum of frequency as that of lightning because of the continuous nature of the frequency spectrum of the lightning.So the lightning could strike such objects as well.So something is missing.What is it?

 

[T.M.Haja Sahib]

There's one other item I would like to bring out.

EMP!!! "Electromagnetic Pulse?

While many of us are very familiar with the term NEMP or "Nuclear Electromagnetic Pulse? from movies, and it is a fact of life, but only a few understand that lightning also creates this same pulse just many times weaker, and if you want to look it up its called LEMP or "Lightning Electromagnetic Pulse?

The reason I bring this up is this pulse is what causes more electronics damage then the actual lightning, sure direct strikes can cause a catastrophe of physical damage, but many strikes are not direct, in fact it is starting to be believed more and more that near field strikes are the major cause and more frequent as we are running into more electronic damage then we see physical damage, in a near field strike this EMP will induce current into any wiring that is in a loop just like a transformer, but at a very high frequency, this may set up circulating currents in a run of cable such as NM and interconnected equipment such as networks, TV cable, phones, and even audio components of a home theater system like the audio cable running between a amplified sub and the main system, the bad thing is that this pulse will use all the conductors of a cable as one wire, this completely by passes any TVSS protection that this equipment might have (how many seen equipment damage while plugged in to a surge strip while other equipment plugged in to that same strip had none?) If you would have been looking you would have seen equipment with other pathways such as phones or TV's and yet a stand alone computer or laptop with wire less networking wasn't damaged, this is a very good sign of a near field EMP strike, maybe to a tree out in the yard up to 200' away.

Now protecting from these LEMP's can be very hard to accomplish after the building is built, sure there are things that can be done after the fact but will not be as effective as designing from the beginning, most of what was learned by the military to block NEMP's applies to lighting EMP's but if you ever get into this field you can see how over whelming it can be, a HF EMP can get through the smallest crack on the shielding and the open Faraday cage in a previous post would not shield from this also.

What this has to do with ''Okay.This may make it clear.''That was a single conductor not sized in accordance with NFPA 780 taking a direct hit from lightning.'' ?

 

[hurk27]

There is one problem:the 15' tall tree with branches of many different lengths acted as a broad band antenna to attract the lightning with a spectrum of frequency.If it were tuned to a single frequency,the lightning would have missed it.But still, many other objects around the tree could also be tuned to the same spectrum of frequency as that of lightning because of the continuous nature of the frequency spectrum of the lightning.So the lightning could strike such objects as well.So something is missing.What is it?

While I said this is not yet fully understood, but I would say that the "tuned" pathway having the lowest impedance at the frequency at the time of the strike may play a big part in which "tuned" pathway gets hit, could be which builds up the ions first like the differences in two close but slightly different capacitors building up a charge, the point in the cloud to the point on the ground can make a difference to which gets hit, there are so many variables.

What this has to do with ''Okay.This may make it clear.''That was a single conductor not sized in accordance with NFPA 780 taking a direct hit from lightning.'' ?

This was just a Tibet of info I just through out there that can also create a hazard on a job site, EMPs can cause HV build up in wires, steel ropes on cranes, or any other conductive items that a worker might be contacting during a strike, and just grounding it may not eliminate the hazard.

 

[jumper]

Including me.:lol:

In that case, you will fit in fine here.

 

[T.M.Haja Sahib]

but I would say that the "tuned" pathway having the lowest impedance at the frequency at the time of the strike may play a big part in which "tuned" pathway gets hit

Consider this.A tower and nearby ground.The impedance of tower-ground combination is always greater than ground alone.But lightning can hit both individually.The current lightning theory explains this in a different way.

This was just a Tibet of info I just through out there that can also create a hazard on a job site, EMPs can cause HV build up in wires, steel ropes on cranes, or any other conductive items that a worker might be contacting during a strike, and just grounding it may not eliminate the hazard.

Do you not believe in the principle of operation of Faraday cage?

 

[don_resqcapt19]

You keep using the word "theory" and that is a very good thing as we really don't understand lightning and lightning protection systems. In fact a few years ago the CMP for NFPA 780 voted to withdraw the standard at the proposal stage because there is a lack of technical information to support the current theories of lightning protection.