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Old 16-07-2021, 09:04   #61
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Re: Near misses of lighting - use ferrite beads to reduce induced voltage spike?

Quote:
Originally Posted by mhsprang View Post
...
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.
Simply put, you want reactance between the threat and the victim. You don't want reactance in-line with an intended lightning conductor.

Actually, popularly used ferrites will have a hard time developing enough voltage across them to cause an arc. But, saying that, even an aircore wound inductor, in the face of a fast risetime 40kA, I suspect would arc over. Ferrites can and do get hot however. I've also had one of my own ferrite cores change its permeability, losing effectiveness permanently, due to a lightning strike.
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Old 16-07-2021, 09:10   #62
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Re: Near misses of lighting - use ferrite beads to reduce induced voltage spike?

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Originally Posted by carstendenmark View Post
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)
YES, on the keel steel. About the best you can hope for. The paint is not helping, but I tend to think that there is so much keel to water surface area, that taken together, should be effective. Also, even if its "insulated by paint", it is a giant capacitor, with a thin dielectric, that will not insulate against the voltages we are talking about.

I use several of those DIN rail mounted double pole breakers on 12V. Note that the DC voltage rating might be only 10% or so of the ac rating, but still is fine for 12-24V dc.

Speaking of floating MINUS. My boat has switched PLUS and MINUS to both engines and the house bank. I don't know why the French do that

Your other question on bonding. The classic answer is to bond "large" metal things together. This technique tends to reduce flashover, from the main lightning down conductor to other,, random metal parts. Part human safety, part equipment safety.. You really want the ENTIRE boat with all the parts in it, to jump up in voltage simultaneously. Yes, to multi-kV levels vs the sea. This method reduces the chances of smaller (power and network) conductors dealing with high currents. That will most always be bad news.
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Old 16-07-2021, 09:34   #63
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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
Surge Protection Device.

Basically a varistor and a surge protection diode in parallel in an aluminum box (single channel version of the 7 channel showing inside). I started off with 20 volt devices and one day was looking at the schematic diagram of a Raymarine autopilot and they used an 18 volt varistor in the 12V feed. Figured if 18 Volt was good enough for RM then 18 was good enough for me. Only of academic interest, difference between 18 and 20 volt protection level.

Since the varistors usually fail shorted you want them down stream of a fuse. Pick something at the 5 to 10 amp level and important that you will notice is no longer working (like electric toilet ).


Frankly
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Old 16-07-2021, 12:02   #64
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Re: Near misses of lighting - use ferrite beads to reduce induced voltage spike?

Something I have been working on for the next boat is to use a large capacitor with an inline resistance for discharge to protect against this very topic.

Car audiophiles have driven cap technology to the point of being able to project against lightning and static build up.

Large scale wind turbines also use capacitors to protect their equipment.
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Old 16-07-2021, 23:30   #65
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Re: Near misses of lighting - use ferrite beads to reduce induced voltage spike?

team karst, I get from you, that I have to connect the bonding system to the mast lightning protection system (mast to keel).
Leaving the DC system separated from bonding bars and mast/keel.
(So far there are no AC system installed.)
Is that ok ?

I think that the magnetic induction field from the lightning bolt running through the metal parts just reaches out to some extent.
You work with protecting of substations from lightning.
In what distance from the "rod-to-ground" (mast to keel) system do you suggest to protect the electric/electronic parts ?
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Old 17-07-2021, 01:06   #66
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Re: Near misses of lighting - use ferrite beads to reduce induced voltage spike?

I found this ad :



Eliminates strikes !

- Just another scam product ?
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Old 17-07-2021, 04:20   #67
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Re: Near misses of lighting - use ferrite beads to reduce induced voltage spike?

This has been a real educational read and I have learned alot....on old style heavy metal hulled craft, I have heard the entire vessel acts as Channel for the strike to travel to the water. then I have heard that when struck people inside run the risk of being too close to masts or holding the wheel etc....it sounds more like its oftentimes a roll of the dice if a crew member is in the wrong place!? Can anyone share a laymans explanation with a rather luddite sailor whether the roll of the dice analogy is accurate or is there more to it on metal vessels!? thanks! Safe sailing to all!
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Old 17-07-2021, 05:35   #68
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Re: Near misses of lighting - use ferrite beads to reduce induced voltage spike?

MTO, etc, etc. This product is known as a "dissipater". It tends to respond to high electric fields by concentrating the field at the sharp points and ionizing the local air. There is another type that used a small radioactive source to help the ionization process.
Neither has proven to reduce the strike frequency. But, both do get sold!

There is another product out there that attempts to "predict" a lightning strike. That one actually does work, and is science based. Very popular product to protect humans at golf courses and ball fields.
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Old 17-07-2021, 05:52   #69
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Re: Near misses of lighting - use ferrite beads to reduce induced voltage spike?

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This has been a real educational read and I have learned alot....on old style heavy metal hulled craft, I have heard the entire vessel acts as Channel for the strike to travel to the water. then I have heard that when struck people inside run the risk of being too close to masts or holding the wheel etc....it sounds more like its oftentimes a roll of the dice if a crew member is in the wrong place!? Can anyone share a laymans explanation with a rather luddite sailor whether the roll of the dice analogy is accurate or is there more to it on metal vessels!? thanks! Safe sailing to all!
My friends 70' ketch was hit, in my waterfront neighborhood, 2 years ago. Steel hulled, and had significant damage in the shore power and 12V systems. Steel has the advantage of "fire proof", but unless special considerations are given the wiring, they are still at high risk levels from a strike. In this case, shore power presented a much lower resistance to earth, than even the large steel hull into seawater.
Step 1: give the strike several, high conductivity paths to water. From high to low. Do not put a FRP hull in the way of multi 10's of kAmps at a million Volts.
Step 2: isolate with air distance any electronics you can. Don't plant radios with high antennas in the middle of the nav station MFD's, black boxes, etc. Run masthead wiring in plastic conduit for isolation. Bundling a coax with SeaTalk is very bad....
Step 3: Use wireless networking whenever possible.
Step 4: Bond systems together at the point(s) near the water conductor. AC/DC/network/down conductors/metal tanks/motors/stays/steering gear/gensets.
Stay/shroud chainplates should be part of the "down conductor" and suitably connected to a near waterline metallic fitting and also connected to ships bonding. Become familiar with the "Georgia Copper" product line.
Step 5: Minimize copper based networking.
Step 6: Use surge protection devices at the local level; within a few feet of the susceptible device. DC feeds, antenna, to chassis.
Step 7: Favor "in the box" as opposed to "networked" data sources. IE: get a VHF with built-in GPS and AIS, rather than a multi-box, networked solution. Tend not to use antenna splitters for the same reasons.
Step 8: Include NEG side fusing on high risk items, like the VHF and others that could deal with a direct strike current. Even fused, a small length fuse will not break lightning current, but could help limit wiring and other device damage within its capability. The job of BONDING is to deal with the very high currents, by bringing up the ENTIRE vessel up to the same potential during the strike event. Its a tough order, but ultimately, $ spend in this area is effective.
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Old 17-07-2021, 09:02   #70
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Re: Near misses of lighting - use ferrite beads to reduce induced voltage spike?

I recommend installing a breaker panel surge suppressor that you would install on the breaker panel in your home.

They are cheap and work really well!

Typically cost $50 to $100 USD and supress 50 to 100 KVA.

I live on the Mississippi Gulf Coast, had a lightning strike take out my HVAC controller, and installed a Square D surge suppressor. It has saved me a number times and only cost $57 USD.

Cheers!
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Old 17-07-2021, 17:02   #71
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Re: Near misses of lighting - use ferrite beads to reduce induced voltage spike?

Hello Team Karst,

Thank you piping up and for sharing your knowledge. I also have a couple of question to make sure I understand some details.


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Step 2: isolate with air distance any electronics you can. Don't plant radios with high antennas in the middle of the nav station MFD's, black boxes, etc. Run masthead wiring in plastic conduit for isolation. Bundling a coax with SeaTalk is very bad....
I was considering running my plastic conduit with a foil shield. I generally use EMT for all my networking on land as an EMF shield. I thought a thin foil inside the conduit was a good idea...

Quote:
Originally Posted by team karst View Post

Step 8: Include NEG side fusing on high risk items, like the VHF and others that could deal with a direct strike current. Even fused, a small length fuse will not break lightning current, but could help limit wiring and other device damage within its capability.
Is there a practical size fuse that might work?

Thanks,

Ben
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Old 18-07-2021, 05:28   #72
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Re: Near misses of lighting - use ferrite beads to reduce induced voltage spike?

Thin aluminum foil doesnt last long in a marine environment. True even inside coax. I would tend to favor a length of 3/4” electrical pvc flex with no metal content.

On the neg side fusing, use same values as POS side. For a vhf, about 7 Amp.
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Old 18-07-2021, 05:39   #73
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Re: Near misses of lighting - use ferrite beads to reduce induced voltage spike?

Great thanks,

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Thin aluminum foil doesnt last long in a marine environment. True even inside coax. I would tend to favor a length of 3/4” electrical pvc flex with no metal content.
I guess I should have mentioned I was researching dielectric epoxies. (I realize I maybe working toward tuning my mast into a capacitor). My plan is to fabricate the tube as part of the mast fabrication.

I don't really want to go into details. I have seen what can happen to simple Refrigeration topics
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Old 18-07-2021, 07:32   #74
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Re: Near misses of lighting - use ferrite beads to reduce induced voltage spike?

Sounds like part of a more sophisticated project [emoji16]
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Old 18-07-2021, 12:54   #75
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Re: Near misses of lighting - use ferrite beads to reduce induced voltage spike?

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Sounds like part of a more sophisticated project [emoji16]
Fine line between sophistication and hare-brained, only time will tell.

Thanks for your comments.

Ben
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