TVS Diodes for Lightning Surge Supression?

[hellosailor]

The PolyPhaser protectors work. That's why the broadcast engineers use them. There are also similar home=brew designs using the air gap in a spark plug instead of the vacuum-gap in the PolyPhaser. Either way the idea is to protect you from GROSS strikes, like lightning, by providing a "gap" to ground that will not pass low voltage, but effectively is no longer a gap when a zillion volts sees ground waiting on the other side of it.


Using a diode across your power lines, is what is called "crowbar protection". Think of it this was: If you throw a crowbar across the power leads, that's going to create a dead short and blow the fuses right on the spot, right?


Same thing when you use a diode. Assuming the diode DOES NOT VAPORIZE before the fuse on that circuit can blow, the short-circuit presented by the diode voltage being exceeded (and a 15V zener diode can be one way to do that, as ordinary alternator surge protection) will cause any reasonable fuse on that circuit to overheat and blow. It may take several seconds for a fuse to do this, so using a minimal-sized size, or a fast-blow fuse type, is advisable as well.


But up the mast? Or at the bottom of it? Sure, a PolyPhaser and a short fat ground cable would be the most professional solution, short of unplugging the cable and grounding it directly. The antenna will still be vaporized, the cable will still be ruined, but everything "beyond" the PolyPhaser should be perfectly healthy.


(Ignoring the possibility of a flash-over or damage from power following other paths!)

[msponer]

Thank you guys!

I've been reading a whole lot on the Internet, but a lot of it is either above my head or makes me suspect the source. It's hard to tell if someone is a charlatan if I don't know anything about it. I read two reasonable looking papers, one from NASA (of all places) that say the metal brush 'ionic disipators' (or whatever) don't do anything.

Let's say I am stubborn and am bent on spending <$500 and <10 hours making my metal boat more lightening resilient. No matter how much anyone tells me it's a useless exercise.

Shall I:

1. Install a Polyphase VHF Suppressor at the base of the mast
2. Install telecom style DC suppressors at the mast for the nav light wires coming inside
3. Add TVS Diodes to every circuit
4. Add quick disconnects to the powerleads for electronics, leave them (and their antennas) disconnected at anchor in the San Blas
5. Add an aluminum strap at deck from the mast to the aluminum hull (I read that on a boat lighting protection site, that was selling them...)
6. Wear a tinfoil hat
7. Buy cases of beer to cheer up if everything gets fried

I think I can do any two in that budget -- which would be the least useless or waste of time and money?

PS -- Do any of you guys understand why the installation diagram for the telecom style DC suppressor has 20A fuses on it? It seems wrong. And these have a 1kA rating, where the straight TVS diodes have a 15kA rating. What is "better"? Photo attached.

Thanks again!

[AnchorageGuy]

HS, An interesting solution, but how will this help with attachments and grounds from the various rigging attachment points and the ground system on the boat, which is usually attached to the mast, rigging and even to stanchions. And how will this protect from streamers, or side flashes that can come from almost any metal objects on the deck?

[hellosailor]

Anchorage-
The idea is to provide a direct ground path (through the PolyPhaser, which has trivial resistance to a strike) immediately from the main charge to the ground. If "this" path goes straight to ground, and "that" path has to take a few turns and detours, the entire strike tends (tends!) to go down the direct path.
How effective will vary with your vessel and your luck, but the point is that it OFTEN works 100%, especially if the Polyphaser can be put at the start of the path, i.e. at the base of the antenna cable and then to a ground. that won't keep the strike out of the rigging, but it will keep it out of the radio and connected instrument circuits. Similar ground paths installed at other points (perhaps from the chain plates to the ground) would similarly encourage other strikes to go direct to ground.
There's nothing certain about lightning except "it happens" but you can certainly encourage it to happen one way rather than another.


ms-
Keep reading, it is a good habit. Remember that disconnecting your power, radio, antenna cables is all well and good--but only if you GROUND the incoming wires and cables. If you disconnect the antenna cable, as many radio operators would do, you should also be able to just move it over a short distance and plug it into a direct GROUND connection. If you just leave it swinging, expect the strike to emerge from it! Often just as a nasty little shocking flash, not the whole thing, but still enough to upset anyone who gets near it.


The fuses on the surge protector are easy. Anything can fail "welded" shut, and start a fire. The fuses are there so that if the surge protector fries, it won't take the rest of the power system with it. Once you've seen a few of the really "that can't happen?!" power failures, you really start to believe in fuses.(G)

[trifan]

msponer -

No surge suppression is worse than some suppression. Having said that, you have to understand that millions of volts and a gazillion amps makes its own rules about what is, and is not, a good conductor and what is a good ground. In a boat you assume that the water is the ground and it is. How that gawdawful flow of electrons get from the cloud to the water is what is of issue here. The main path just might go from mast, through the rigging and down to the water but it is moving so fast that the impedance of that path may be higher at that instant than another that you hadn't considered.

Then there is the main strike going where it is supposed to but adjacent current flows going where they shouldn't. When you are dealing with magic that intense, any success you have is a matter how favored you are with God.

Surge protectors and lightning arrestors can't hurt and in many instances (less than direct hits) actually help. All I am trying to say that if your boat takes a direct strike your electronics will probably get fried. Make sure you have really good insurance for that eventuality.

[dannc]

If you have not read Kasten about lightning, here ya go, Lightning Attenuation Onboard. Don't miss the links at the bottom of the page.

Later,
Dan

[Lake-Effect]

A friend runs a marine electrical business. One year, a boat in the middle of a row at a yacht club took a direct hit. All the service business he got from that row paid most of the cost of a new van.

[foufou]

A more likely solid solution is to "connect" the rig to the salt water. By connect, I would use a wire or cable or chain equal in thickness to the rigging and dangling in the water. This could be attached to a snap shackle and deployed as needed. Lightning takes the shortest least resistant path- though not without collateral damage. One suggestion I have herd of is to put all electronics in a Faraday Box. This is a steel box where magnetic and electrostatic fields stay on the surface of the box. One sailor suggest that an oven might be a close approximation to a Faraday Box. Unfortunately these are often not very large. good luck, may the force be with you..F

[darylat8750]

I built a cabin on a ridge in the mountains. We get lots of lightening strikes up there. The power company offered to sell me a surge protector to mitigate lightning strikes. It was quite large and weighed at least 30 pounds. I asked the foreman of the crew if it would do any good. He said "Well, if the line gets hit a couple of miles away it might. But if it hits on your pole or one just a couple of poles away, nothing will help."

One of my neighbors had several well grounded lightning rods on his house. Whole system was designed by a prof of electrical engineering and installed by the owner who is a prototype machinist. It was the envy of the neighborhood. Lightning struck the top of their masonry chimney (which was lower than the nearby rods) blew stones off on the inside that knocked holes in a wall 30 feet away. Every piece of electronics in the house was toast. Best laid plans of mice and men.....

[EwenT]

Originally Posted by msponer

You no doubt know more about this than I do, but I believe the protection from the TVS diodes is that they short circuit the + and - leads if there's more than a 15 volt difference between them. So when the 1 kazillion volt lightening surge runs through the + or - wire, the diode clamps and sets the voltage difference between the wires to ~0-15 volts. So that's all the device see's, even though it's + and - are a kazillion voltes above everything else. And the failure mode is that the diode clamps permanently, and continues to short circuit the leads after the lightening passes: continuing to protect the device, but also tripping the breaker and making it inoperable.

Do you know different? I majored in physics, which sounds fancy until you know that I am one of those guys that only graduated from college because my professors liked me...

I feel that the telecome/cell tower folks wouldn't buy the DC suppressors if they were snake oil. I mean, at some point, someone smarter than me has to decide it's worthwhile to install them in their equipment. But then, they have a different environment from a boat sitting in the middle of an anchorage. Maybe they have more near-misses than a boat would, and that's where the DC surge suppressor works. And maybe the suppressors only work for near misses. Or in an environment where the main part of the strike is already routed to a big fat pipe in the ground. I don't know.

This whole thing is, like, way beyond what I know.

You have accurately described how TVS diodes work. These are basically zener diodes with additional metal added for heat dissipation. If too much energy is absorbed the metal fuses, creating a short circuit. Otherwise they are good for multiple strikes. How much energy they can absorb is not easy to determine. For example, the 15KPA17A diode that I suggested for Domino has a "Peak Pulse Power Dissipation by 10/1000μs Test Waveform" of 15000W. The easiest way to interpret this is in terms of current since the 10/1000μs waveform referred to is the test current used to get this rating. Since the clamping voltage is 17V, then the critical peak current is P/17=900 A if the lightning current has a 10/1000μs waveshape, that is, a risetime of 10μs and a fall time of 1000μs. Virtually all direct lightning strikes have larger peak currents than 900A. So as a means of protecting against a direct strike, TVS diodes are woefully inadequate.

However, indirect, or induced effects are a different story. These arise from magnetic fields that couple into the circuit and depend on the time derivative of the current: so the pulse is much shorter than 10/1000μs, maybe 100 times shorter, resulting in a much larger critical peak current. But the mechanism is also different and the energy that the TVS needs to absorb is proportional to the area of the circuit and inversely proportional to its distance from the conductor carrying the lightning current. In a nutshell - reduce the spacing between wires in each circuit (also twist wire pairs), and move the wires as far from the closest lightning conductor as possible.

A note about Domino. While as a pro bono service I did suggest the components that should be used , I was not involved in their installation and see a couple of fundamental errors in this respect. So I do not endorse the methods shown in their blog.

[Rapanui]

Surge arrestors can improve protection. As many have said, nothing will protect against a direct hit, but they can protect against a nearby strike which induce high ground currents. It is the nearby strikes that are in the majority of course. I used to be involved in designing traffic electronics and all our stuff was fitted with surge arrestors and fitted all over the world including high lightning places and it worked. The critical thing is how many joules of energy the arrestor can absorb, the higher the better.
The best advice you have had is to consult a specialist and adopt his scheme. Also, you need to be able to regularly test the protection is still ok and carry replacements for where they have done their job.
I think you are wise to protect as much as possible and not rely on insurance alone. While insurance may replace the kit, it can take a long time just to find out what has been damaged and it might be you actually need it at the time. Anything that improves the odds is then worthwhile.

[FlyingCloud1937]

You are very passive/aggressive.

Originally Posted by msponer

Really? Thank you for your input, I appreciate having a reality check on the conversation, but I feel you are being unnecessarily hostile. Why?

I am asking questions because I know nothing about lightning protection. Is anything better than doing nothing? Or is everything futile? If anything is possibly helpful, about how possibly helpful, and how much time and money is it to do?

I am not asking for advice on how to construct a dowsing rod. Lightning suppressors exist. Trifan said he's designed them, and then also said they sometimes don't work. But are they completely futile? Why would people pay him to add them to a device if they are worthless? I see lightning suppression modules for sale for cell towers. There's an IEEE standard for lightning protection. So someone must think you can do something. In some cases. Are those cases at all like what an anchored boat experiences? Or no -- in the case of boats -- does nothing work well enough to even bother trying?

I don't know.

[Miniyot]

Originally Posted by msponer

Really? Thank you for your input, I appreciate having a reality check on the conversation, but I feel you are being unnecessarily hostile. Why?

I am asking questions because I know nothing about lightning protection. Is anything better than doing nothing? Or is everything futile? If anything is possibly helpful, about how possibly helpful, and how much time and money is it to do?

I am not asking for advice on how to construct a dowsing rod. Lightning suppressors exist. Trifan said he's designed them, and then also said they sometimes don't work. But are they completely futile? Why would people pay him to add them to a device if they are worthless? I see lightning suppression modules for sale for cell towers. There's an IEEE standard for lightning protection. So someone must think you can do something. In some cases. Are those cases at all like what an anchored boat experiences? Or no -- in the case of boats -- does nothing work well enough to even bother trying?

I don't know.

I am a land based electrician so I know a thing or two about lightning protection. The cell phone towers and TV/radio broadcast towers are grounded as well as the electric service to a land based house. Grounding is the primary means of lightning protection. It gives lightning the path that it wants, just to hit the earth. The wires used for grounding these towers can sometimes be as large as 4/0, which translates into 1/2" in diameter.
All of these little doohickies, doodads, and geehaws that are sold in stores or handmade might as well be the equivilant of a divining rod or a palm reader or a psychic card reader. Lightning just traveled 10 miles through the air and some people think a 1/8" gap is going to stop a bolt of lightning....

Think about this. would you rather be on the recieving end of a lightning strike with nothing but that little doodad between you and that bolt (lasts less than a second) or get tased for 3 seconds (Those prongs are close to a 2" gap)? My response would be "tase me bro" 40,000 volts is a heck of a lot less than a million volts. Just a little info....a taser will damage 12 volt electronics an that arc will travel more than an inch.

However, all that being said...

If it makes you feel safe, then go for it. As for me I would rather all my equipment to be properly grounded.

[colemj]

Originally Posted by msponer

It seems like bidirectional ones would be better, in case the surge is on the ground side of the circuit…?

Lightning surge will almost assuredly come in through the ground side of the circuit. After our strike, we could trace the path completely through the ground side - enter the boat through the VHF coax shield, jump from the VHF into the boat ground (most likely through the case), blow the fuses on the negative wires while leaving the positive wire fuses untouched, enter electrics through the case ground and exit through the engine ground taking out the alternator's internal regulator.

And that was only the surge component of the strike. The main strike exited the boat through our direct mast grounding system.

In autopsying a couple of other boats (including Domino), they too had the surge come through the negative side of the circuits.

Mark

[colemj]

Originally Posted by Miniyot

Think about this. would you rather be on the recieving end of a lightning strike with nothing but that little doodad between you and that bolt (lasts less than a second) or get tased for 3 seconds (Those prongs are close to a 2" gap)? My response would be "tase me bro" 40,000 volts is a heck of a lot less than a million volts. Just a little info....a taser will damage 12 volt electronics an that arc will travel more than an inch.

I got a bit lost here. I think the discussion was about adding surge protection to individual circuits (or whole panels) AFTER the boat was bonded to ground for lightning purposes. I don't remember anyone suggesting that a surge protector or air gap could serve solely as a direct strike protection.

Mark