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· in the wilderness
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61 Posts
Discussion Starter · #1 ·
In 16 years, our power system has been ultra reliable. Our Trace Inverter has never let us down. It was with a great deal of consternation that I watched our power system suddenly start kicking on and off the other night. A light and dishwasher which were on at the time cycled on and off with the inverter. Bummer I thought!

I'm pleased to report that the inverter is working just fine again. Here's why I think we got lucky. We have our wind turbine which sits on a 67 foot steel pipe tower. Our inverter started acting squirrelly during a lightning storm. I suspect, but have no way to know for sure, that we were building up a charge and likely were very close to a lightning strike. The inverter sensed something funky.

Fortunately, I realized the lightning storm and inverter problem might be related and I powered down everything pronto. I usually power down routinely during a major thunderstorm but this one didn't seem to be a big deal so I left the power on. I always unplug computers and critical equipment every lightning storm.

For what it's worth... we have some pretty vicious thunderstorms in the summer and although the lightning cracks all around, we have never been hit. I have lightning rods on the roof as well as chimneys with appropriate stranded copper cable to a grounding rod in the earth. Our electrical system is tied to the same point. We have a lightning arrestor indoors with our set up.

The turbine tower also has a lightning arrestor connected across the output of the turbine. I also have a heavy gauge stranded copper wire that runs to the top of the tower which is grounded. This wire is bent 90 degrees at the top and sticks out about 12 inches. I took the strands and splayed them out in kind of a roundish fan pattern. In theory, my understanding is this set up will bleed off any charges before the big bolt drops from the sky. So far-so good.
 

· Business Owner
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3,438 Posts
You were VERY lucky! Sounds like your tower was getting hit by stepped leaders (pre lightning strike electrical discharges) The voltages were spiking on your system, causing the invertor to trip offline. Definitely a good plan to disconnect everything when you are having a lightning storm.

Sounds like you have a good setup on the grounding and lightning rods.

Just FYI, lightning charges can also enter "backwards" from the ground into the ground rod and then out thru your system. I had a customer a few years back that had that happen. Lightning hit a tree in the park behind their house, came in thru the cold water pipe in their kitchen, went into a 120v AC line to the dish washer and then backwards thru the lightning protectors into the phone and cable TV lines, eventually damaging TVs, VCRs, Computers, and phone equipment.
 

· Preparing
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10,971 Posts
You were VERY lucky!

Just FYI, lightning charges can also enter "backwards" from the ground into the ground rod and then out thru your system. I had a customer a few years back that had that happen. Lightning hit a tree in the park behind their house, came in thru the cold water pipe in their kitchen, went into a 120v AC line to the dish washer and then backwards thru the lightning protectors into the phone and cable TV lines, eventually damaging TVs, VCRs, Computers, and phone equipment.
This really happens????? OMG !!!! I hope you're not just kidding because now I'm really concerned.

I just live in a regular on-grid house. How can I stop lightning from coming into my house backward? We have tall trees everywhere in our backyard.
 

· Proud deplorable ilk
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9,205 Posts
Short answer is nothing.
You can add surge supressors to your panel ( whole house) a lightning suppressor at the meter base, change your receptacles where electronics are plugged in to surge suppressor style, and have an electrician verify proper grounding and bonding of electrical system to include water lines, gas lines, phone, cable, conduits feeding outbuildings, any thing conductive entering the house.
Do you have flexible gas lines at stoves, dryers, fireplaces, water heaters? Each of these locations can ignite with a lightning strike if not properly bonded and improper installation.

Best bet, unplug everything you can during a storm.
 

· in the wilderness
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61 Posts
Discussion Starter · #6 ·
Thank you for all the responses. I should add that in addition to unplugging items, I flip all the AC circuit breakers as another small layer of protection. I understand a bolt could jump the breaker but why make it any easier. I also flip the battery main breaker and disconnect battery power to the inverter and solar regulator. We are 100 miles in the bush so any strike will likely be catastrophic. I didn't have the presence of mind to peek out the window but it might have been an interesting show at the top of the tower.

Yes, that's the proper term. Stepped leaders. Couldn't remember that but I do think that was our situation. About as close as I care to come to being hit. Many years ago, a tree next to my parents house was hit and it did follow back into the house. Ruined phone, computer, kitchen stove and other stuff. Good thing family was home because the kitchen stove went full on and the only way to turn it off was at the breaker. As Donfini mentioned, all we can do is make sure things are well grounded, lightning arrestors are in place and hope for the best. Good banter and info. Thanks!
 

· Business Owner
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3,438 Posts
This really happens????? OMG !!!! I hope you're not just kidding because now I'm really concerned.

I just live in a regular on-grid house. How can I stop lightning from coming into my house backward? We have tall trees everywhere in our backyard.
Donfini is pretty much dead-on in his assessment above. Good surge protectors will help, but aren't a bullet-proof shield against a direct lighting strike, or even an indirect "super bolt" lighting strike - a positively charged lightning strike.

Most lighting strikes from cloud to ground are negatively charged, that is - the lighting is negative and the ground is positive. About 10% of lightning strikes are positively charged, where the lightning is positive and the ground is negative. These positive lighting strikes are far more damaging and more lethal. The customer's house I mentioned was likely a positive lighting strike, as was a house hit on a friends house last year. It hit outside across the street and took out a long list of electrical appliances in their house. It set their security system on fire.

The best advice for protection, is to unplug anything important during an electrical storm. Proper grounding and bonding of electrical grounds to each other is also essential. My customer's house actually had an improperly installed ground to the electrical panel that contributed to their damage. I installed a new ground rod at the panel, and they haven't had any more issues, even with additional lightning hits in the park behind their house over the last few years.

In some areas, tall trees have lighting rods installed in them and a heavy cable is run to the base of the trees to ground rod system. You might look into that. Contrary to popular belief, lightning rods aren't primarily designed to take a lightning hit. Rather, they are designed to bleed off the voltage buildup and prevent a lightning strike. Failing that, they reduce the severity of a lightning strike, if it occurs and provide a safer pathway to ground.

I recently noticed our local college has gone crazy installing lightning rods all over the campus buildings. Very high density too. Like every 12 ft on the roof lines. I wonder if they know something we don't? It seems that a lot of the storms we have had recently have had much more lightning in them than in years past.

Back to the OP, I don't know how it would affect your system, but I know some people with wind generators have shunts that they can short the power leads coming down to stop, or severely slow the blades down if they need to for maintenance or excessively high winds. I would think a shunt that grounds both sides might be a good idea to use in locally intense lightning storms. Thoughts?
 

· Thinking outside the box
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766 Posts
At a previous residence I had a radio tower where I had a separate rod connected to Neon lamp and then to ground. Since Neon lamps light at 90 volts it would light up when lightning storms were in the area. Eventually I placed a photo resistor cell next to the lamp and connected it to an audio oscillator. Every time the lamp would light it would emit a tone. It worked for many years letting me know when a storm was approaching.
 

· in the wilderness
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61 Posts
Discussion Starter · #9 ·
Brian, Our turbine is fantastic but the controller was junk. I wrestled with it for a good year and finally tossed it. I bought a Midnite Classic with Midnite Clipper. It is an amazing set up. I was able to program the power curve and it works superb. The Clipper has a breaker to stop the turbine. As well, there is a separate breaker going to the batteries.

So essentially, I can stop the turbine to a slow spin and completely disconnect from the batteries. It's another way I buffer the rest of my system from any potential strike.

2muchstuff... Cool idea with the neon bulb and oscillator. You could probably set it up that the brighter the lamp, the more output from the photo resistor and the higher pitch from the oscillator. If it became shrill- time to head to the bunker. :)
 

· Registered
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Watch out for "solid state" lightning arrestors. They don't react as quickly as the old spark gap ones. The old phone company ones had 2 carbon blocks with a 6 thousandths of an inch, as I recall, gap between them. Could survive many hits. Lots of today's crap fails after one hit, and you don't notice it as there's no indication given by them.
And the surge protectors using MOVs are virtually useless in my opinion.
 

· Proud deplorable ilk
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9,205 Posts
Here's some info on the flexible gas lines

http://goodsonengineering.com/wp-content/uploads/2011/08/p379-Goodson-TB1140_web.pdf

If you have a lightning strike and damage to your home, it has to be checked very carefully and throughly. The panel and all wiring needs megger checked and the results documented.
Ask for a copy.
Circuit breakers can be tested by a UL facility, but it would be cheaper to replace them.
I have seen many cases where the house needed rewired after a direct strike.
It's your house, so don't let insurance companies bully you into only checking the area they think was hit.
The entire system may be affected, same as anything plugged in that has a circuit board.
( just about everything has digital controls)
 

· reluctant sinner
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23,403 Posts
A lady I knew rented a duplex. Her service entrance took a direct strike. It had resistance heating in the ceiling. The entire resistance heating was scorched black in the most awesome pattern. Anything in her apartment that was plugged in was toast - even stuff that was not running like a hair dryer. This was back in the early 90's. I think they rewired the whole apartment and she got all new appliances.

A local store near by had all the freezer and refrigerator fried when a turkey shorted out the power lines about 20' from the store. Flaming turkey set brush on fire to boot. Lucky the owner was there and had a fire extinguisher handy or the store and her house would have burnt down too. She no longer feeds them or encourages them to hand around.
 

· in the wilderness
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61 Posts
Discussion Starter · #14 ·
CarlMc,
Part of my background is electronics so I still have my Fluke meter. That's the only method I have available to check grounds.

It's been 16 years since I bought the lightning rods and copper cable. It was a company that specialized in lightning protection so I'm confident it is proper size but I can't give you gauge.
 

· Registered
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How do you know its got a good electrical bond to earth? Corrosion varies by soil type. Good grounding when it comes to lightning isn't simple. The lightning ground rod needs to be electrically separate from the electrical system ground.
 

· Proud deplorable ilk
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· Thinking outside the box
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766 Posts
Lightning strikes direct or indirect can do strange things that will make you scratch your head. I have had several indirect strikes over the years. The strangest one was where it bypassed everything in the house and blew out the water level circuit board on the washing machine in the basement.
 

· If I had a voice I'd sing
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7,160 Posts
You need separate lightning and electrical system grounds. Having the tower on its own ground is also good.
That answers the question I was going to ask, thanks! :D:

So how DO you test the effectiveness of ground rods? A mega-ohm meter, like I used to use in the Navy? They had a hand crank on them to generate a very high voltage.
 

· Registered
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If you have more than one ground rod, this is easy. Merely measure between each of them. Having them several feet apart for this purpose is good, but a couple feet apart is okay. 25ohms or less is your target. Let us know what you get, as well as your spacing. It's best to test your rods with equipment made just to test ground rods, but you can learn a little with your multimeter providing you know what you're looking at. Keep in mind that your meter can't push any real current through the circuit, which is where the right equipment comes in. Your meter will also pick up residual current flow through the earth that distorts the signal. The codes somewhere say that if you have two ground rods for the system (each system, that is) you can more or less skip the resistance measurement, so that might be an option to renting/borrowing/hiring the equipment.

The issue is that your tower has a lot of current flowing through it, and there'
s a big resistor on the bottom, which is called the soil. The ground rod itself has a voltage potential somewhere between the top of the tower and the soil itself some distance away. This voltage between the various components we collectively like to mentally lump together and call "ground" is the source of all kinds of unhappiness. The more current there is flowing between the air (static charge) and the soil (your tower is a conductor with resistance, just like your wiring, just like your ground rod) the higher the voltage across each of these pieces will be. Put something electronic or what have you in that path somewhere and you will begin to learn about ground loops.

The quality of your connections is also a very big problem, since copper conductors corrode like crazy being out in the weather. If you want to see a ground rod go away(corrode to nothing) in a few weeks, pass current through it constantly. That reminds me. You need to use your ammeter to confirm that you have no current flowing through your ground rods under normal conditions. As to the tower ground path, it's normal to get some slight DC current since the air is usually electrostatically charged all the time.

In my day job, I work with really high currents doing lightning simulation for aerospace, so even a "big" wire (the word means little to me) has resistance and therefore a voltage drop across it. Most ground wires that people use are relatively tiny, so have high resistance. You lose little by spending the money up front to put a heavy ground on the tower and a lot to save in your power system if bad things happen.

Two things to do a little research on:
Ground loops
testing ground rods
 
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