lightning rods vs surge suppressor

[rios]

What is the difference in surge suppressor and lightning rod protection? Is one better than the other?

 

[Dennis Alwon]

A surge suppressor takes surges in the lines from lightning or whatever. Lightning rods don't suppress surges but rather supposedly attract the lightning away from the house to the rods. Of course, if lightning makes a direct hit nothing really works.

 

[rios]

Thank you

 

[LISHAJI]

What is the difference in surge suppressor and lightning rod protection? Is one better than the other?

Lightning rod protects the structure it's installed on from getting lightning stikes and if it does get one, it provides a least resistant path to ground; while surge suppressor protects the device it is connected across from all surges. Both won't work if they are not connected to an effective grounding rod!!

 

[K8MHZ]

Lightning rod protects the structure it's installed on from getting lightning stikes and if it does get one, it provides a least resistant path to ground; while surge suppressor protects the device it is connected across from all surges. Both won't work if they are not connected to an effective grounding rod!!

I disagree. Surge suppressors don't need a ground. Ground rods are terrible connections to the earth, although better than nothing. A well designed system will employ a grounding system (not just a ground rod) and both arrestors and suppressors. Air terminals (lightning rods) are usually area dependent. They are not used here on buildings, but I see them on electrical sub-stations. The ones on the subs are about 8 feet long, tapered, rounded at the end and a couple inches in diameter. They are bonded to the rods in the concrete and to the metal framing. The conductor is about a 2/0. Any hit that lightning rod would take would blow a ground rod right out of the ground.

 

[hurk27]

Lightning rod protects the structure it's installed on from getting lightning stikes and if it does get one, it provides a least resistant path to ground; while surge suppressor protects the device it is connected across from all surges. Both won't work if they are not connected to an effective grounding rod!!

Lightning rods do not lower the amount a building will receive a lightning strike, while there are some companies out there that make this claim it has been tested to be false, there only purpose is to intercept a strike and safely drain it away from taking paths through the structure by providing a path the Earth outside of the structure, But such a close encounter of a strike will still cause induced currents in the buildings wiring that can damage electronics, and lightning does not have to even strike a building to cause this, as it is known as a Near Field Strike and can be caused from lightning striking as far as 300' away from the building.

Surge suppressors only react to higher voltage between the conductors they are connected to, a reference to Earth does not come into play, a lighting strike ahead of a transformer will produce a surge on its secondaries that will have no reference to Earth as a path for current flow, as transformers are isolating they will also turn the lightning into an isolated voltage surge that now does not reference Earth, so the grounding electrode system has no effect to helping surge suppressors do their job even though this is claimed by many, the only case that a reference to Earth would help is in a direct strike, I doubt that very few TVSS units would withstand a direct strike and provide much in the way of protection.

Another tidbit on Near Field Strikes, is that most of the damage caused by this form of strike is an induction of current into multiple paths between circuits, or between other conductors like cable TV and networks, or phone systems, any system that forms loops that the current from a near by lightning strike can induce current into can be affected, and the problem to protecting these is that it will treat each cable as one conductor thus rendering surge suppressor useless, lets take one of the more common damage items found In a near field strike, lets say we have a couple TV's connected together by coax, each of these TV's also are on two different circuits ran different paths back to the panel, at the panel they are connected to the same phase, neutral and grounding terminals, with the coax we have now one big loop, with the TV tuners the weak point of the loop, any lightning strike close by can induce current into this loop, and each conductor path will act a one conductor like the secondaries of a transformer, the lightning strike point of attachment is the primary, since the secondary is isolated from the primary just like in a transformer it no longer references Earth, so any electrodes will not help with trying to dissipate this energy, and since the current is being developed in each cable as one conductor, a surge suppressor has no effect other then providing some protection from any voltage difference that might develop between the hot/neutral/ground in each cable, but the most voltage will hit the tuners of each TV.

I have been on a few cases like above where both TV's were protected by surge suppressors and even had a whole house protection where the lightning struck a tree out in the yard but did not show any signs of traveling into the house, as it was on the far side of the building from the service and or any of the incoming communication cables, and in every time it took out the tuner of these TV's but left them able to turn on, damage several phones and PS but not harm one GFCI or computer on a wireless network, while damaging the router and a couple computer network cards but not damaging anything else in the computers.

In the above the only things that were damaged were things that had more then one path way to the device.

So in essences I would say that isolation such as wireless, fiber, and other methods would go along way to prevent most of the damage a near field strike can cause.

 

[K8MHZ]

In the above the only things that were damaged were things that had more then one path way to the device.

That's why SPG (Single Point Grounding) is used in a properly designed grounding system.

 

[hurk27]

That's why SPG (Single Point Grounding) is used in a properly designed grounding system.

While true and used to prevent loops, but as we all know, many of the above mentioned loops occur within the structure when the networking and cable and phone takes different paths through the structure then the power conductor.

A SPG system will have the greatest effect on a all metal structure or one that has a Faraday cage that can shield these internal loops, but most homes and business wont have this. I still promote SPG in all installations, and most utility's here also come close by routing all conductors to a building to allow bonding to the service, which is about the best your going to get in this area, unless you have engineering spects that say otherwise.

 

[K8MHZ]

While true and used to prevent loops, but as we all know, many of the above mentioned loops occur within the structure when the networking and cable and phone takes different paths through the structure then the power conductor.

A SPG system will have the greatest effect on a all metal structure or one that has a Faraday cage that can shield these internal loops, but most homes and business wont have this. I still promote SPG in all installations, and most utility's here also come close by routing all conductors to a building to allow bonding to the service, which is about the best your going to get in this area, unless you have engineering spects that say otherwise.

Here, we are required to provide an inter-system bonding connection to our GEC for the other systems and they are required to connect to it.

That helps a bunch.

Correct cable routing and power configurations can help. For instance, plugging your computer into a different receptacle than a cable connected printer can create a hazard, as the printer cable is shielded and that shield is grounded, making a great place for a ground loop. The shield is also not designed to carry current and will become a fire hazard with just a few amps being carried through it. That also means that even if the computer is unplugged, it is still somewhat bonded to the printer and vice versa.

I have discussed this at length for many years with many people, as being in ham radio is subject to lightning discussions ad nauseum.

Here is what it boils down to. Any system can be made safe from lightning, even direct hits. Cell towers, weather radar, aircraft radar, etc., all function fine while taking direct hits.

The system used easily cost more than the stuff it protects. Just the engineering alone can exceed that cost.

For the average homeowner, the best protection of equipment for the amount of money spent is insurance. The same holds true most small businesses. You will spend far less money insuring your equipment than you will trying to protect it. There are also aesthetic issues. A truly effective lightning protection system can be less than pleasing to the eye and may not favor well with people that are finicky about appearances.

 

[LISHAJI]

I disagree. Surge suppressors don't need a ground. Ground rods are terrible connections to the earth, although better than nothing. A well designed system will employ a grounding system (not just a ground rod) and both arrestors and suppressors. Air terminals (lightning rods) are usually area dependent. They are not used here on buildings, but I see them on electrical sub-stations. The ones on the subs are about 8 feet long, tapered, rounded at the end and a couple inches in diameter. They are bonded to the rods in the concrete and to the metal framing. The conductor is about a 2/0. Any hit that lightning rod would take would blow a ground rod right out of the ground.

I must agree that, surge arrestors are among the most misunderstood and misapplied protective devices. Typically, IEEE C62.11 1-4 classes of SPDs, are made up of varistors whose resistance reduces as the implied voltage increases. This reduction in resistance continues until surge is present, just like a direct short to ground. Upon reaching this condition, the surge energy diverts to ground away from the protected equipment, thus reducing the effect of the overvoltage.

If you want to understand the use of Air Terminal for tall structure as per NFPA 480-4.1.1. The following video would explain the science behind lightning protection.

http://youtu.be/zhu5pIrPw7U

 

[LISHAJI]

Lightning rod protects the structure it's installed on from getting lightning stikes and if it does get one, it provides a least resistant path to ground; while surge suppressor protects the device it is connected across from all surges. Both won't work if they are not connected to an effective grounding rod!!

Sorry correction , I meant surge arrestor not surge suppressor, and ground rod was refering to the grounding system!!

 

[kwired]

This reduction in resistance continues until surge is present, just like a direct short to ground. Upon reaching this condition, the surge energy diverts to ground away from the protected equipment, thus reducing the effect of the overvoltage.

I would not use the term "ground" in that statement. The device simply shunts the surge current across itself. If one lead happens to be "ground" then that is where current is flowing. Otherwise it is just flowing between the two conductors the varistor is connected to, and hopefully more is flowing there than through the protected equipment.

If the surge voltage or duration is too high then the varistor becomes a casualty to the event and the protected equipment is subjected to whatever surge level is still available. That is with simple varistor, there are devices more complex that may still protect the equipment and well as indicate there is some damage to the surge supression device.

 

[stickboy1375]

You can waste your money any any device you want, but lightning always wins. I had an 8k dollar insurance claim last year, thats what homeowners insurance is for...

 

[K8MHZ]

You can waste your money any any device you want, but lightning always wins. I had an 8k dollar insurance claim last year, thats what homeowners insurance is for...

Even cell towers, radar installations, etc, that operate while taking direct hits are insured.

 

[djd]

djd

djd

IN the case stated where you had tuners affected, would a surge suppression on coax "indvidual" line protect that individual tuner in the tv you were talking about, or ?

 

[hurk27]

IN the case stated where you had tuners affected, would a surge suppression on coax "individual" line protect that individual tuner in the TV you were talking about, or ?

In this case no, because the induce voltage treated the coax as one conductor of the loop, the surge suppressor for cable only protects between the center conductor and the shield, the coax was one path the power cord was the other path, no TVSS units are design to protect between these two paths.

 

[WIMaster]

What is the difference in surge suppressor and lightning rod protection? Is one better than the other?

They should be used together.

An extensive GROUNDING and BONDING SYSTEM along with surge protection will help to Minimize losses.

A thorough study of NFPA 780 and Soares is highly recommended.

I have a customer that swears they took a direct hit and complained that one of their GFCIs tripped due to it. I asked if anything else was destroyed or damaged that they knew of. They said no, but were still complaining about the outlet. To keep them happy I replaced the outlet, but thought highly of how well the lightning protection SYSTEM worked.

 

[LISHAJI]

If the surge voltage or duration is too high then the varistor becomes a casualty to the event and the protected equipment is subjected to whatever surge level is still available. That is with simple varistor, there are devices more complex that may still protect the equipment and well as indicate there is some damage to the surge supression device.

This is another concern with SPD; to determine whether it has got degraded, after a major surge event. SPD should be coordinated with a fuse. Since fuses may be about 500 times slower than SPD, after a major surge, with ths SPD having diverted the surge energy, the fuse might blow, at the tail end of the surge. Thus a blown fuse should be an indicator that a surge event has sucessfully been taken care off, and it's time to replace the SPD!!

 

[tom baker]

Lightning rod protects the structure it's installed on from getting lightning stikes and if it does get one, it provides a least resistant path to ground; while surge suppressor protects the device it is connected across from all surges. Both won't work if they are not connected to an effective grounding rod!!

A minor point - a lightning protection system uses earth terminals.
A major point - as pointed out, a SPD does not need a ground to operate at the service. The service neutral is grounded via the main bonding jumper. If there is a surge from the utility, the SPD shorts from line to line and sends it back to the utility, or from line to neutral and sends it back. The SPD also converts some of the surge overvoltage into heat.

 

[LISHAJI]

A
A major point - as pointed out, a SPD does not need a ground to operate at the service.

I agree, this is true at the point of service, however consider , the protection downstream, for eg., a submersible pump installed 200ft below grade. The casing of the pump would be at a lower grounding impedence than the service ground. Since service grounding impedence cannot change during a fast rising surge due to inductance, the potential difference between the winding, which is reference to the system ground, and the grounded motor frame, would become enough to cause an insulation failure. Thus L-G, L-G-L & N-G connection of SPD is very crucial .