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Old 15-07-2021, 06:57   #46
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Re: Near misses of lighting - use ferrite beads to reduce induced voltage spike?

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... Lightning ionizes the air to make a conductor out of it; it doesn’t need copper bands to find it’s way, it will take the shortest path. In case of a wooden or fiberglass boat, this can sink it.

Lightning basically tries to find the path of least resistance (not necessarily the shortest), as it travels down to the ground.
But this is not always a straight line, because air is not a perfectly homogeneous mixture.

There are fluctuations in temperature, humidity, pollutants, dust particles, etc. in the air, and so the resistance varies. As a result, lightning strikes are often observed in a zigzag pattern ('tortuosity').
The zig-zag line is actually a sort of optical illusion The real path looks more like the course of a meandering river.

Each discharge is a series of steps, in which the current travels a short distance, and then pauses: each pause is where we see a change in direction. Meanwhile the local potential to ground is changing, so the final target is constantly changing.
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Old 15-07-2021, 07:08   #47
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Re: Near misses of lighting - use ferrite beads to reduce induced voltage spike?

I have a marina neighbor; who is an electrical engineer, that connects stainless steel chain to his standing rigging and hangs the chain in the water as a lightning mitigation. 3 per side.
He swears by it.......does anyone else do this?
He is a pretty smart guy but he is the only one I've ever seen who uses chain as a lightning mitigation.
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Old 15-07-2021, 07:40   #48
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Re: Near misses of lighting - use ferrite beads to reduce induced voltage spike?

Living in Florida for nearly 60 years I have observed a number of lightning strikes. In this case looking at not only the discharge thru the sky but the actual receipent of the strike. On the receiving end of the strike, if it is a well grounded/ conductive structure (transmission line tower for example), there is no visual evidence of the strike as it travels down the conductive structure. Seen a lot of dirt fly at the bottom. If the receiving end is a poor conductor (tree for example) you will observe the strike all the way to the ground.

My take away from this is your best chance for controlling an unfortunate visit from Zeus is to provide him a good conductive/ low impedance path to his desired destination (the surface of the ocean, better than most soils). This is not any original thinking with me, as lightning strikes are safely conducted to earth/ water every day over the entire planet. Modern sailing craft are blessed/cursed with an important first component just have to finish the job.

As to induced voltage damage "you pays your money and takes your chances". Don't think anybody would take issue with switching both positive and negative power leads moves the ball a little in your favor (fusing both sides not even a close second). While I worry about network wiring, because they are usually twisted and shielded they are on the lower end of my protection priority list.

Only sure fire solution, sell yacht and watch cable TV in a grounded shipping container.


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Old 15-07-2021, 08:00   #49
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Re: Near misses of lighting - use ferrite beads to reduce induced voltage spike?

What happens in a strike at sea??
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Old 15-07-2021, 12:49   #50
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Re: Near misses of lighting - use ferrite beads to reduce induced voltage spike?

I"ve done a little dabbling with lightning. Actually, my other job, besides keeping the boat floating, is protecting electronics within electrical substations from lightning and other mayhem. I became even more interested in lightning when my radio station took a direct hit, while living in West NY of all places. This is a place where people run to the windows to look at thunderstorms, they are so infrequent there.

Anyway, this thread is filled with wild mistruths. Although there is certainly the element of random luck, there is a fair amount of science in lightning protection. In the end, its $ of risk management that "may tend to work". Cell sites get it near 95% right, btw.... NASA got it around 100% right. So, it can be done.
Fundamentally, give the high energy bolt somewhere safe to go. Metal, thick, highly conductive, and do NOT stop it inside the hull, the way the manufacturers do. ie: are your chainplates connected to big cables, straight to the sea, or just above? How about the base of your mast? These are the primary, first steps, and unfortunately, it can't end there. You have simply increased the chances that the boat will not sink. The electronics may still fuse...

Yes, there is a place for ferrites, although those, as noted before will not become very effective below 1MHz. Lightning has significant energy content up to about 1MHz, but much more closer to DC. I'm guilty, as most others, to have a VHF antenna at the highest point on the mast. The VHF radio has a sensitivity of around 0.5uV, (MICRO volts) and a damage threshold of around 10Volts. That is a ratio of around 10 million to one. Now, add lightning. Now,we are asking the VHF to accommodate a MILLION times a MILLION overvoltage. Not in our world will this happen. So, oblivious to this fact, we run the coax down the mast into the middle of our nav station. Its folly to think that is a good idea for lighting mitigation.

that's it for page 1.
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Old 15-07-2021, 13:26   #51
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Re: Near misses of lighting - use ferrite beads to reduce induced voltage spike?

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Thank you Bill,

I'm working on a topology fo a marine network and this first hand information gives me an idea of what to expect.

You have answered all my questions.

Enjoy your day,

Ben

We are thinking/wondering what to do about ours. Some have noted that a double pole protected power supply might prevent what we had. However, with our AIS on and connected to the network, there's just not a good solution. I think I'll ping Raymarine and ask them if there's a reasonable way to isolate our AIS... Since the repair work is being done by a certified marine electrician (insurance is paying for it and I'm tired of fixing it), I can run it by him, too.

If you have any thoughts, feel free to contact me via PM, or email. Email is first and last name, no punctuation, at gmail.
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Old 15-07-2021, 13:33   #52
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Re: Near misses of lighting - use ferrite beads to reduce induced voltage spike?

Good post, Karst. Since my first post is probably lost in this thread, it's important to note that like us, you are about 10X more likely to get damage from a spike from a neighboring boat that got hit. We are one of 5 others that got damage, when it was another sailboat that took the strike. Fortunately, there were empty slips, and some boats had only minor damage.
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Old 16-07-2021, 06:52   #53
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Re: Near misses of lighting - use ferrite beads to reduce induced voltage spike?

We witnessed a catamaran being struck at the masthead at the anchorage in Dry Tortugas this summer during a freak thunderstorm in the middle of the night with more lightning than I've ever seen in a 3 hour period. A second boat was also struck in the anchorage, but I don't have details on that one.

The catamaran had the Strikeshield system deployed and were dragging on their anchor at the time, as were MANY of the boats with winds gusting from multiple directions above 40 knots.

The wife was on the trampoline and the husband at the helm. They reported that they could see a bright flash in the water around the Strikeshield. Neither were injured in the strike. There were no holes found in the boat and no water ingress. Once the engines were shut down they would not restart. Black box electronics damaged. Chartplotter and other helm electronics damaged. I believe the charger/inverter was ok. Electronics panel was still working. Fridge compressor ok.

I know of at least 3 other boats with Strikeshield system deployed that were hit by lightning. It appears that a strike protection system provides protection against a hole being blown in the fiberglass, but all had significant electronics failures.

During thunderstorms we try to place handheld VHFs, IPads/computers/phones, and any other sensitive electronics in the microwave. Don't forget to unplug the microwave. This acts as a Faraday Cage.
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Old 16-07-2021, 07:28   #54
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Re: Near misses of lighting - use ferrite beads to reduce induced voltage spike?

Frankly, I looked at your pictures. Lots of little boxes labeled SPD. What is in the box and what is SPD?

I Googled SPD which was entertaining:
Symphysis Pubis Dysfunction
Sensory Processing Disorder
State Personnel Department
Seattle Police Department
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Old 16-07-2021, 07:36   #55
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Re: Near misses of lighting - use ferrite beads to reduce induced voltage spike?

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Originally Posted by StoneCrab View Post
Frankly, I looked at your pictures. Lots of little boxes labeled SPD. What is in the box and what is SPD?

I Googled SPD which was entertaining:
Symphysis Pubis Dysfunction
Sensory Processing Disorder
State Personnel Department
Seattle Police Department
Sozialdemokratische Partei Deutschlands...
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Old 16-07-2021, 07:42   #56
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Re: Near misses of lighting - use ferrite beads to reduce induced voltage spike?

From what I know of electronics, a ferrite bead by itself is not likely to help.

Coupled with thyristers, or other overvoltage protection, proper fusing, shielding, and grounding they can likely at least limit the high frequency peak giving other protection time to respond.

As for those who vehemently post of this board "nothing is going to protect against a direct strike by a super bolt", yeah, your right, but I've gotten dozens of near misses, and zero directs so far.

It's the near misses that take out one or two of your very expensive marine electronics that's the issue here.

If my radar, and vhf survived, but my chartplotter, and depth finder didn't, what's the difference?

Luck?

Placement?

The VHF most certainly got some voltage from the mast top antenna.

Why the chartplotter, it's in the helm, (but it's connected to literally everything else on the boat).

The only thing I can guess is the VHF is expected to get a little voltage surge, and has internal protection where the antenna goes in.

So why doesn't everything? Cost?

Can we add protection? Yes.

If $20 worth of ferrite beads plus a bank of heavily grounded thyristers save my $2,000 chartplotter even once, it's money well spent.

Both the military, and Avionics have millions in radar, and navigation equipment in a location hit by lightning nearly weekly, but hardly ever get lightning induced failures. Why?

Extensive grounding, and overvoltage protection everywhere a wire enters or leaves a shielded, grounded metal box containing sensitive circuitry.

So can we protect against lightning on a sailing vessel? Yes.

It just takes time, money, effort, and know how.

If the US Navy can do it, so can we.
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Old 16-07-2021, 07:47   #57
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Re: Near misses of lighting - use ferrite beads to reduce induced voltage spike?

page 2;
Once one has succeeded in providing a good, albeit close path for lightning current to pass to the water, a review of the electrical system on the vessel is in order.
A medium size bolt is on the order of 30kAmps of current, for around a couple hundred microseconds. And, usually, several strikes are taken. So, even if a good path is obtained to the sea, you are left with a very large magnetic field to contend with. In addition, those secondary bonding conductors may develop significant voltage drops from end to end. So, the math turns the situation into a devastating event, rather than a catastrophic event. The triad of considerations are "culprit", "victim", and "transmission path". Its the transmission path of the energy that is the hardest to manage in a boat. Plastic boats with distributed electronics are extremely complex devices in this sense. Self-contained, battery powered, non-wired electronics have a very good chance of survival. But, those are few and far between, limited to HH VHF, and a portable GPS or two. Those survive because of the lack of a high current path thru the device, and the lack of external "antennas" that are efficient at lightning frequencies. The microwave/oven storage can help, but is not even necessary in most cases. There just is not much energy transfer into the device to cause issues.
But, the real world demands remote sensing, and networking; and both are huge issues for protection. NMEA0183 has some degree of built in isolation, at least in the early days. By using optoisolation IC's, you can get 2kV or so of effective isolation from the transmitter to receiver. But that was then, and now is a new world of higher speed COMM. NMEA2k, using CAN as the backbone, is nowhere near as tolerant of peer to peer voltage differentials. Like maybe 7volts operationally, and maybe 15V before damage will occur. We need a couple orders of magnitude higher than that for real lightning protection, on a secondary level. So, forget that as being helpful. Note that the masthead may have a wind sensor that ultimately connects your entire portfolio of electronics, even the VHF, to the strike landing point. The ethernet based systems are quite a bit better, and use small isolation transformers, but the spacing is not yet good enough.
So, what electronic device trends are positive? Wireless: WiFi, BT. These give you air isolation from peer to peer, at least on the COMM/networking side. This is hugely effective in lightning mitigation. A closeby, rechargeable 12V source, only connected to the house batts when charging is required, will make this a much more bulletproof system.
At some point in this mitigation strategy, you can reach a point where internal box fixes have value. The ferrites, the gas tubes, the MOV's. But, don't expect a gas tube across the 12V power line will somehow save you when the boat is not bonded, has no paths from masthead to water, and has long copper networking cables in place. Its lipstick on a pig. And, by all means, if you have masthead antenna(s), isolate those cable runs, and isolate that radio. Distance, and eliminate copper networking. Buy a VHF that contains its own GPS, and NOT an external one.
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Old 16-07-2021, 08:13   #58
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Re: Near misses of lighting - use ferrite beads to reduce induced voltage spike?

Inserting ferrites might make things worse! A lightning strike does not induce voltage, it induces a current. And that current is high. A current creates a voltage the moment it passes a resistance (or impedance, for AC currents). So when you want to fight a near strike, you need to pass the induced current to ground. This is what surge arresters do.


Now, if you place an inductor in series with a wire that picks up the induced current, it meets a resistance caused by the ferrite. So a high voltage is built up across the ferrite. In worst case, you could get a flash over across the ferrite. You don't want that.
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Old 16-07-2021, 08:24   #59
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Re: Near misses of lighting - use ferrite beads to reduce induced voltage spike?

Mentioning the mast-to-water connection (by team karst) - does my cast steel keel work as a good ground plate (just painted and anti-fouled), when connected by two very thick copper cables, mounted properly in both ends, running straight down from the alu mast foot ?

If yes, will it then be beneficial NOT to connect the bonding bus (seacocks, etc.) to the mast or keel ?
So, mast grounding system one thing, bonding system another thing, not connected ?

My theory of this is that the main lightning bolt entering the masthead will follow the straight path to the water (the keel) and hopefully leave the bonding system just slightly induced.


Another question :

My negative DC is not connected to any bonding or grounding.
Is standard 230V household double breakers suitable as switches for a 12V DC system ? (See photo)
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Old 16-07-2021, 08:57   #60
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Re: Near misses of lighting - use ferrite beads to reduce induced voltage spike?

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Inserting ferrites might make things worse! A lightning strike does not induce voltage, it induces a current. And that current is high. A current creates a voltage the moment it passes a resistance (or impedance, for AC currents). So when you want to fight a near strike, you need to pass the induced current to ground. This is what surge arresters do.


Now, if you place an inductor in series with a wire that picks up the induced current, it meets a resistance caused by the ferrite. So a high voltage is built up across the ferrite. In worst case, you could get a flash over across the ferrite. You don't want that.
Well, I am taking about near-hits, and then the magnetic field created by the flash will induce a voltage and that in turn will create a current. Not the other way round.

And yes, the ferrite could be damaged in the process, but they are cheaper to replace.
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