EMP-proofing my system with tvs diodes design idea

Nakinto

Solar Enthusiast
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Feb 15, 2021
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38
Reddit, that was your only problem, going on there for anything that requires an IQ over 12 is not a great idea.

That said, I love all the ideas on here, especially the TVS and capacitors. I have only heavily grounded my system, two 2/0 copper grounds on the solar array, #4 wire between each panel, and a 2/0 at home. The idea of adding a TVS, MOV and capacitor bank on the negative and positive lines to ground them if they got a high voltage spike is an interesting idea, wish I had thought of it. I have never worked with TVS before so will have to look into those.

Hedges, I wish I had as much knowledge as you do... I can follow you but I don't have that deep of an understanding of the components!

Also, my electronics (for the solar) are all inside a motorhome with an aluminum frame and I added a full cover of 1/4" hardware cloth around the whole frame then grounded it with a 2/0. Hopefully that is a good enough faraday cage :)
 

Hedges

I See Electromagnetic Fields!
Joined
Mar 28, 2020
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Shh! Don't tell him he'll survive EMP only to succumb to chronic beryllium disease.


But seriously, I think transients coming in on AC and DC wires are the largest threat to the system.
Any self-respecting prepper wouldn't build a bunker adjacent to Trestle or any locations anticipated to be ground zero, so I doubt it would be exposed to fields that could affect the electronic components directly.

 

Hedges

I See Electromagnetic Fields!
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10,692
In my research I stumbled across this video.


He showed sine wave input up to 270 Vrms into a 120 Vrms circuit. The current into his selenium clamp showed it drawing up to 32A, following a clipped sine wave.
That indicated to me the 270 Vrms signal was high impedance, around 5 ohms.
Poking around, I haven't found figures for what TOV can drive. But I don't expect them to be so current limited.
 

Maast

Compulsive Tinkerer
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In my research I stumbled across this video.

Huh, I wasnt even aware of selenium cells. It seems they would provide a current sump for the long lasting E3 portion or CME until the main breaker tripped. Very good find, thank you! Going to have to read up on them.
 

A.Justice

Swears he didn't start that fire.
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Slightly off topic, but I used the D.O.E EMP Resilience Guidelines as a starting point for making my system able to handle surges. It's a really good read, and they clearly did a lot of research on the topic. I've been watching this topic, and it goes over my head a little bit, but I see a lot of the same things mentioned in that document.


I just moved out of DC, where if there were to be an attack, no matter how well I isolated/insulated, even my phone should be fried if it was not in a cage.

It was a good time to leave The District anyway.
 

Maast

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Slightly off topic, but I used the D.O.E EMP Resilience Guidelines as a starting point for making my system able to handle surges. It's a really good read, and they clearly did a lot of research on the topic. I've been watching this topic, and it goes over my head a little bit, but I see a lot of the same things mentioned in that document.


I just moved out of DC, where if there were to be an attack, no matter how well I isolated/insulated, even my phone should be fried if it was not in a cage.

It was a good time to leave The District anyway.
Thats pretty much a 'executive level' document that doesnt give out any details of how to accomplish their 'action plans'. I'm down in the component-level datasheets trying to find components that can be added to provide E1/E2/E3/CME protections and it's proving to be a tough slog. HEMP E1 hardening is very difficult and I'm looking at about $400 in components not including the Midnite lightning arresters if I just want to throw money at it.
 

RogueDFW

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Deveak

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AFAIK geomagnetic storms are issue only for large-scale grids. Even a large DIY solar system has tiny wiring loop area compared to national scale grid.
20 volts per kilometer potential is not much for DIY installation.

5000nT/minute magnetic field change(Carrington event scale) is also next to nothing for small system.
0.000005 T change over 1 minute to 10m2 loop generates 8 microvolts
https://www.omnicalculator.com/physics/faraday
Can I get a little more info? Sorry I am a complete laymen. So far from what I see, the max expected induced voltage is somewhere around 50k volts per meter of wire or am I wrong? I am more worried about nuclear EMP, I live off grid. I would estimate my solar system has less than 1000 ft of wire and less than 3000 for the house. Assuming worst case scenario and just a ball park number, what voltage would I be looking at?
 

EricBarbour

overqualified for this
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free advice from someone who specified AC mains power equipment for minicomputer installations:

By all means, install beefy transient absorption devices. Good MOVs with gas-filled spark gaps plus passive filtering. Make sure there are solid earth grounds for the filtering. Drive a new ground rod next to your installation and connect the filtering and suppression to it directly with a short, FAT, straight copper wire.

But if you really seriously expect to have problems with nearby lightning strikes or other major overvoltage events, you will be best served with an isolation transformer. Best are the ferroresonant voltage-regulating types (Topaz, Sola etc). They are costly, heavy, run very hot and waste some power, and thus tend to have short lifetimes. But they are the gold standard for protecting electronics from mains overvoltage and slow-risetime transients. Mission critical computer installations commonly use regulating transformers BEFORE the UPS or anything else.
 

TGPB

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I'm from the school of "Better to have it and not need it, than to need it and not have it." This is why I have backup components in cardboard boxes, inside metal boxes, inside metal containers. I have Midnite Solar lightning protection on my solar combiner box as a minimum protection. I would be extremely interested if someone came up with an EMP protection method for an Off-Grid system. The whole idea of having a BOL is having a refuge in case of a catastrophic event. Anything to help harden a BOL perks my interest and curiosity.
 

Diysolar123

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you are working on a problem that has already been solved many times but only for those with really really deep pockets.
For everyone else the answer is much simpler, you cannot "protect" what you have entirely, so you design in sacrificial components and those get replaced from protected storage.

near lightning strikes will cause splash damage that will couple to every wire you have, that includes internal wiring in devices. An input powerline filter or ups will not help. Every usb cable, network cable, audio cable, and power cable are suddenly the source of a voltage spike.

ham radio operators as a group probably have the most "consumer" grade experience with dangerous voltages, power filtering, and running computers while you also have them attached to what are basically lighting rods sticking up in air. I have had to replace many "arc plugs" and have replacement equipment disconnected and stored in a metal box ready to go. I use usb isolators, my network is fiber to my computer, I have suppressors and powerline filters (inlcuding some nice old fashion beefy filter transformers), I use the optical spdif audio output of my computer...
and I know that when I get the next nearby lightning strike, I will lose some equipment... as has happened 3 times already and those where only hitting trees about 30-50feet from the house hehe

buy replacement equipment when its on sale and store it "offline" ;)
 

larfme

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Feb 10, 2021
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I've been back-of-the-envelope designing supplemental EMP and transients protection for my system using tvs diodes in conjunction with the Midnight lightning arresters (I can build them cheaper than just buying them, but they're inexpensive and the time savings is worth it). I recently saw video on Sol-Arc inverters being "EMP proof" and realized all they really did was include about $15 in tvs diodes to do it.

The Midnights MOVs clamping voltage is something like 470v, which is fine for common mode events like nearby lightning but do nothing for high voltage transients in the grid power lines.

A common mode event is where high voltage is induced in both the positive and negative lines - thus no voltage differential between components. To receive a UL rating among other things the component/system has to be able to withstand a 3000v common mode event without damage.

The design elements include:
MOVs over time wear out from high voltage transients, TVS diodes do not wear out.
MOVs can handle more sustained current in an event. TVS diodes do okay but not as well as MOVs
MOVs reaction time is 8-12ns, TVS diodes are 2-10ps
High alt nuke EMPs rise time is in the ps range, faster than MOVs can react.
Tvs diodes sustained current capacity is dependent on how hot they get
Lightning can strike anywhere in the world. I was living in Iceland and a lightning bolt hit the apartment building next to mine and toasted a modem in my computer and caused damage to the motherboard.

My thought was to encase an array of three to five 300v clamping 1.5kw tvs diodes in a .5"x2"x3" block of thermal transfer epoxy to act as a thermal mass and have one going between each power conductor to earth ground for the PV array, 48V lines, and the in/outgoing AC lines. Each one would cost about $20 in materials - most of that being the epoxy.

In an EMP event the idea is the TVS diodes would clamp just long enough (before saturation or burnout) for the MOVs to begin conducting and short the overvoltage to earth ground. In addition the tvs diodes would clamp any transients thus protecting the equipment and keeping the MOVs from degrading. My primary goal is transient clamping, the EMP protection is a highly desired "just in case".

Thoughts?
This guy has a bunch of videos explaining how to protect from EMP, including solar setups. https://youtube.com/user/disasterprepper
 

Ted Katsouras

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Apr 19, 2020
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Thats pretty much a 'executive level' document that doesnt give out any details of how to accomplish their 'action plans'. I'm down in the component-level datasheets trying to find components that can be added to provide E1/E2/E3/CME protections and it's proving to be a tough slog. HEMP E1 hardening is very difficult and I'm looking at about $400 in components not including the Midnite lightning arresters if I just want to throw money at it.
Are you planning to put any snap on fairites on your system?
 

Substrate

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SoCal
I hate to say it, but have you done your social engineering after any such event and your system survives?

Ie, being the only guy on the block with power - and with light on at night after a week or so, people can get jealous and you stand out like a light-house beacon and may have to defend your stuff.

Use blackout-drapes, or something similar?

Other methods are probably best left to different forums, but something to think about when people start panicing and losing their morals.
 

Maast

Compulsive Tinkerer
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767
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Washington State
I hate to say it, but have you done your social engineering after any such event and your system survives?

Ie, being the only guy on the block with power - and with light on at night after a week or so, people can get jealous and you stand out like a light-house beacon and may have to defend your stuff.

Use blackout-drapes, or something similar?

Other methods are probably best left to different forums, but something to think about when people start panicing and losing their morals.
Without getting into specifics, I'm fairly rural and I have been a fairly hardcore disaster prepper since 2005. There isnt much I'm not prepared for. I've always simply assumed I'll be feeding the neighborhood (all 8 houses of it) even though half of them are preppers of various levels too. Hope they like beans, rice, and roast beef hash though...
 

NOLA_Castle

Learning Everyday....
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May 26, 2021
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All, do you know what kind of diode for solar panel LG Neon B-LG-320?
the panel has 40.8 VoC; 10.19A short circuit current.

Will this work "10A10 10 Amp 1000V 10A 1KV Axial Rectifier Diode solar panel C16?
 
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