Weird thing 2

JESSICA · October 2010

Another very weird thing happened to me:

Yesterday, there was a fearsome lightning storm in my area. One colossal strike hit the ground close to the house, but there was no direct hit. Grid was off and my pv system was running.

One, and only one of the breakers tripped, the one that provides energy to one ceiling fan and some light fixtures.

Charge controller (mx60), inverter, and everything else continued operating as usual. Delta arrestors did not open.

What could have happened? Why is it that only one breaker tripped? Was it caused by the lightning bolt?

Vic · October 2010

Re: Weird thing 2

Lightning behavior and its effects are very unpredictable.

Commonly, a lightning ground strike is in the hundreds of thousands of Amps of current flow. And the "wavefront" -- the speed at which the field builds up around the strike (essentially) is amazingly rapid. This very fast wavefront induces very large currents in any surrounding/nearby conductor (of electricity).

These induced currents create voltages in conductors. The length of the conductor and the orientation of the conductor in relation to the strike cause large variability in the things affected by the strike. Furthermore, the currents in conductors near the strike also generate smaller currents in other conductors ... and so on. This leads to very unpredictable and unrepeatable effects.

In addition, sometimes electronic items can be damaged by lightning, but a failure may take some time to develop.

Lightning is awesome stuff, and demands a healty respect. JMHO, Good Luck Jessica, Vic

niel · October 2010

Re: Weird thing 2

be very thankful you sustained no damages as enough current to trip your breaker is significant power to damage things. you also have found the weak point in your system that you may want to beef up efforts there for more lightning protection.

JESSICA · October 2010

Re: Weird thing 2

niel wrote: »

be very thankful you sustained no damages as enough current to trip your breaker is significant power to damage things. you also have found the weak point in your system that you may want to beef up efforts there for more lightning protection.

There are not one but 2 Delta arrestors, and a thick and long lightning rod in place.
What else can one do?

Cariboocoot · October 2010

Re: Weird thing 2

JESSICA wrote: »

There are not one but 2 Delta arrestors, and a thick and long lightning rod in place.
What else can one do?

Check the ground connection to the fan unit. I was puzzling over this and came up with the idea the lightning actually induced a current in the fan's armature which back-fed too much power through the wiring and tripped the breaker. If the fan was on, that is. If the motor casing is well grounded it should reduce the possibility. Nothing can eliminate lightning problems. It's powerful and unpredictable.

We get lots of lightning here. That's how several thousand hectares burn to the ground every year.

Seen it do some mighty peculiar things, including make your hair stand on end. If it does that; hit the dirt!

System2 · October 2010

Re: Weird thing 2

JESSICA wrote: »

There are not one but 2 Delta arrestors, and a thick and long lightning rod in place.
What else can one do?

Have you got an actual lightning rod set up with braided copper wire running from corner to corner of your building? If not you probably don't have a real lightning rod set up just a grounding electrode to ground the wiring in your house. I Have installed the lightning rod set up before for a costumer and you should have a 10 Foot 3/4" ground rod at each corner of the house. Then depending on your roof line depends on how many, mini rods i will call them, on your roof. You connect from one ground rod across the roof to each mini rod and down the other corner of the house to the second ground rod. I am sure you can look more info up online about it.w

JESSICA · October 2010

Re: Weird thing 2

Cariboocoot wrote: »

Check the ground connection to the fan unit. I was puzzling over this and came up with the idea the lightning actually induced a current in the fan's armature which back-fed too much power through the wiring and tripped the breaker. If the fan was on, that is. If the motor casing is well grounded it should reduce the possibility. Nothing can eliminate lightning problems. It's powerful and unpredictable.

Cariboocoot:

Yes, the fan was on; but it seems no permanent harm was done, the fan has been working as usual for two days after the close encounter with Zeus wrath.

The strange thing is that another fan was on, on another circuit, and nothing happened to that circuit/breaker.

JESSICA · October 2010

Re: Weird thing 2

dmmcallister26 wrote: »

Have you got an actual lightning rod set up with braided copper wire running from corner to corner of your building? If not you probably don't have a real lightning rod set up just a grounding electrode to ground the wiring in your house. I Have installed the lightning rod set up before for a costumer and you should have a 10 Foot 3/4" ground rod at each corner of the house. Then depending on your roof line depends on how many, mini rods i will call them, on your roof. You connect from one ground rod across the roof to each mini rod and down the other corner of the house to the second ground rod. I am sure you can look more info up online about it.w

Yes and no:

I installed a 3/4" rod, about 8 feet tall (from the roof), and around 12 feet apart from my panels. A very thick cable (I think it is gauge 2) connects the rod to a copper ground rod, wich is 10 feet (more or lees) into the ground.

Nevertheless, there was no direct hit, neither to panels nor to the rod.. In fact, my wife and me actually saw the lightning bolt, aprox. 30 to 40 feet from the house. Belive me, as I said, it was fearsome.

Anyway, thanks for the advise.

halfcrazy · October 2010

Re: Weird thing 2

Was the fan on a standard breaker or is it an Arc fault breaker ? if it is an arc fault breaker i suspect we will see lots of tripping just like we did with the gfi's in lightning storms

JESSICA · October 2010

Re: Weird thing 2

halfcrazy wrote: »

Was the fan on a standard breaker or is it an Arc fault breaker ? if it is an arc fault breaker i suspect we will see lots of tripping just like we did with the gfi's in lightning storms

It is a standard breaker.

In addition, the gfi's in the house did not tripp, though some of them were in use.

JESSICA · October 2010

Re: Weird thing 2

Does lightning ever strike the same place twice?

Yes, it does! Well, not exactly the same place, but very close.

Just last Saturday, a fearsome bolt hit my house. I don’t really know what actually happen, but I think that it split, and a couple millions volts hit the lightning rod and went eventually to ground, but some extra million volts hit my roof, creating a crater of about 2 inches deep x 10 inches wide, and a smaller one beside it.

No harm done to pv panels or any other equipment, though my panels are 12 feet away from the iron rod.

Pics below show the rod, the crater at its base, and one of my Delta arrestors.

Kamala · October 2010

Re: Weird thing 2

Looks like a concrete house?

What is the "slag?" in photos 2 & 3?

I'm building a 30' X 80' steel shed on the highest point on my 40 acres with nothing higher than it in a 500' radius. This is a grid tied structure, no PV or wind.

I asked the general contractor about lightning protection. He seemed to think that since it is steel there would be no issues. Then I think that it might be a great Faraday cage. But then, none of the numerous steel panels are electrically connected. So when a magnificent atmospheric potential chooses to achieve equilibrium with the ground, it will spark across those many unconnected panels.

What then?

K

techntrek · October 2010

Re: Weird thing 2

jessica, its time to move!

Cariboocoot · October 2010

Re: Weird thing 2

Kamala wrote: »

Looks like a concrete house?

What is the "slag?" in photos 2 & 3?

Melted concrete, no doubt. Lightning is fun! :roll:

I'm building a 30' X 80' steel shed on the highest point on my 40 acres with nothing higher than it in a 500' radius. This is a grid tied structure, no PV or wind.

I asked the general contractor about lightning protection. He seemed to think that since it is steel there would be no issues. Then I think that it might be a great Faraday cage. But then, none of the numerous steel panels are electrically connected. So when a magnificent atmospheric potential chooses to achieve equilibrium with the ground, it will spark across those many unconnected panels.

What then?

K

Not to worry; we'll all remember you fondly.

I will not tell you what a steel "quonset hut" looks like after it gets hit; you're worried enough already.

dwh · October 2010

Re: Weird thing 2

Wow. Maybe it's time to build a tower just to draw the strikes and give them somwhere to go besides the house?

mike95490 · October 2010

Re: Weird thing 2

dwh wrote: »

Wow. Maybe it's time to build a tower just to draw the strikes and give them somwhere to go besides the house?

That's what a flag pole is for ! Or a wind gen mast.

JESSICA · October 2010

Re: Weird thing 2

Kamala wrote: »

Looks like a concrete house?

What is the "slag?" in photos 2 & 3?

K

Yes, it is a concrete house (In Puerto Rico, 95% of houses are concrete or concrete blocks). It is at the top of a hiil, almost the highest place in 20 square miles.

I don't really know the definition of the word "slag". I looked it up in the Dictionary: "The vitreous mass left as a residue by the smelting of metallic ore".
If you are talking about the residues of concrete, then I can tell you they filled 2 - 37 ounces peanuts jars.

A friend of mine told me that maybe the lightning bolt hit only the rod, and then some of its force went through the cable to ground but some of it just "exploded" through the concrete. Is this posible?

JESSICA · October 2010

Re: Weird thing 2

techntrek wrote: »

jessica, its time to move!

I think dwh's advice is better.

Nevertheless, there is, in fact, a tall - really tall - tree just around 60 feet away from the house, and it has never been hit by a bolt.

KeithWHare · October 2010

Re: Weird thing 2

JESSICA wrote: »

A friend of mine told me that maybe the lightning bolt hit only the rod, and then some of its force went through the cable to ground but some of it just "exploded" through the concrete. Is this posible?

My guess is that the lighting jumped to rebar in the concrete and vaporized a bit of moisture in the concrete on the way.

Keith

BB. · October 2010

Re: Weird thing 2

I am certainly no expert in Ligthning systems... But I believe you have a couple of things you can do to improve the ground rod installation...

First, I don't think Rebar is a very good lightning conductor. The iron may actually provide inductive impedance to the "high frequency" of the lightning current. Replacing with a copper ground rod may be a better solution.

Second, believe it or not, lightning does not like sharp curves or to change directions.

Drive the lightning rod below the surface of the earth and have the wire/cable approach the top of the rod in a gentle curve and attach to the rod--Do not have the wire approach from the base and go up the side of the rod like your picture. This web page has a rough drawing of the proper way to terminate to the ground rod.

I cannot tell (there maybe other conductors at the top of the rod I cannot see)--But real lightning cable is fairly large diameter and heavily braided (for large surface area of the wire--lighting travels in the surface or "skin" of the wiring). It is not cheap and probably costs around $2-$3 per foot.

-Bill

PS: A sweeping curve is at least an 8" radius (16" diameter).

JESSICA · October 2010

Re: Weird thing 2

BB. wrote: »

you have a couple of things you can do to improve the ground rod installation...

First, I don't think Rebar is a very good lightning conductor. The iron may actually provide inductive impedance to the "high frequency" of the lightning current. Replacing with a copper ground rod may be a better solution.

[You are right. But I have not found a long enough copper rod here in PR. They usually come in 10 feet pieces, how will I mount it on the uppermost level without using wires/cables that will cast a shadow over my panels?]
Second, believe it or not, lightning does not like sharp curves or to change directions.

[Well, there are no "sharp" curves: grounding cables are, indeed, curved, but in an open way (I think!)]

Drive the lightning rod below the surface of the earth and have the wire/cable approach the top of the rod in a gentle curve and attach to the rod--Do not have the wire approach from the base and go up the side of the rod like your picture. This web page has a rough drawing of the proper way to terminate to the ground rod.

Sorry, I don't understand. I have 2 rods: a copper one driven 8- 10 feet into the ground; and the rebar, on the roof; both are connected via 4 # 6 cables (2 at the bottom and 2 at the top (in the pics, you can no see those). I can not just have one rod...

I cannot tell (there maybe other conductors at the top of the rod I cannot see)--But real lightning cable is fairly large diameter and heavily braided (for large surface area of the wire--lighting travels in the surface or "skin" of the wiring). It is not cheap and probably costs around $2-$3 per foot.

[You are right again. I tried to buy "welding cable"; but 25 feet of it (# 2) was more than $100 here in PR. However, you will be right again, if you tell me that $100 is less than the cost of a new mx60 or inverter...!]

-Bill

PS: A sweeping curve is at least an 8" radius (16" diameter).

Thanks for so many wise advices.

dwh · October 2010

Re: Weird thing 2

JESSICA wrote: »

I don't really know the definition of the word "slag".

When welding with a "stick" welder, you have to chip off the "slag".

When you melt metal with impurities in it, the impurities will separate from the metal and form a layer - that's slag.

BB. · October 2010

Re: Weird thing 2

Ok--That iron rod is the lightning rod (or air terminal) itself.

Replacing that rod with copper or aluminum might be better... Ferrous (magnetic) materials like iron and steel become "inductive" with radio frequency current (light lightning) and become less able to let the current flow correctly.

Whether you need to replace the iron rod or just add copper wiring beside it (or even slip a copper water pipe over the outside of the rod--not sure that will work very well) (to well above the roof line, tied to the copper ground wire)--I am not sure. From my two cents point of view--you do not want the heavy lightning current flowing too close to the iron/ferrous materials (or going through, for example, a whole in a metal roof).

Somebody else here, or perhaps a local lightning expert near you can answer that question better.

-Bill

JESSICA · October 2010

Re: Weird thing 2

dwh wrote: »

When welding with a "stick" welder, you have to chip off the "slag".

When you melt metal with impurities in it, the impurities will separate from the metal and form a layer - that's slag.

thank you dwh

In pics 2 and 3 there is no such "slag". The concrete is "black" (actually dark green) because of humidity; the white or bright areas in front of the rod are the "craters" I mentioned, one bigger than the other. How the lightning bolt caused those craters is what I don't know for sure.

The rebar/iron rod is 20 feet long; it protudes almost 10 feet above the uppermost roof, goes through the outer part of the roof (inside a pvc conduit), and then rest on a thick piece of rubber, on the roof of the first floor. As you can see in the pics, two # 6 cables are attached to the bottom of the rod (two more are attached to the top) to conduct the electriticiy to a ground rod, driven 8- 10 feet in the ground.

As BB wrote, there are some curves of the cable; I did not think they were too sharp...

BB. · October 2010

Re: Weird thing 2

The moisture in the concrete was probably heated by the lightning and the pressure forced the surface concrete to pop up (spalled)...

-Bill

dwh · October 2010

Re: Weird thing 2

To clarify a bit - in the U.S. at least, we tend to use the word slag as sort of a generic term to mean, "melted and/or really screwed up".

Shoot a tank with a missile - that tank got slagged.
Short out a battery and fry the cables - slagged.
Car catches fire - slagged.
Big bomb turns sand into glass - we'd call that glass "slag"

mike95490 · October 2010

Re: Weird thing 2

Look up "UFER Ground". It's on the web, and referenced here several locations.

It's using the mass of rebar and concrete in the foundation, as a giant ground.

BUT - the initial piece of rebar, needs to be 1/2 inch, in order to not melt. Additionaliy, it needs to be a 20 foot long length, and either tied or welded, to other rebar in the foundation. It's been found that the ions in concrete. really make a good grounding path, and if your "stub" didn't connect to much in the concrete, that explains why the stroke "jumped off" and went elsewhere. Yikes !

MisterB · October 2010

Re: Weird thing 2

When I was putting up my first wind generator I had to take it down to fix something and raised the tower with the cables left open. As a thunderstorm approaced, I began to hear a funny noise in my house, like some small animal had gotten in. It turned out to be coming from a 12 volt light bulb that was switched off. All of a sudden, the thought of electrostatic build up leading to lightning popped into my mind and I realized I had left an ungrounded conducter 45 feet in the air and ran outside in the rain and disconnected the cables at the tower. Since then, I never raise the tower without everything hooked up. I already had a decent ground but I made further improvements and checked everything.

Grounding rods are copper clad steel and rebar won't do the job properly. I live on a rocky hill mostly made of basalt and I can only drive a grounding rod around 3 to four feet into the ground and the climate here is very dry and grounding rods need moisture in the soil in order to conduct properly so when I moved here the local solar gurus advised me to bury as much #4 bare grounding cable as I could horizontaly to compensate for the lack of vertical depth and dry soil. I started with a 100 foot roll and added from there and drove grounding rods as deep as I could and bonded them to the #4 cable.

The other part of grounding is bonding everything to the ground. If there 2 large metal objects close to each other and they have no electrical connection, such as metal plumbing which isn't grounded and house wiring which is, when lightning strikes, it can induce a huge voltage in one relative to the other which will most likely arc where you least want it to, like through your electrical system frying anything pluged into it, but if they are bonded electrically with good grounding connections, they can't develop a voltage difference between them and the lightning strike will discharge elsewhere.

JESSICA · October 2010

Re: Weird thing 2

MisterB wrote: »

to bury as much #4 bare grounding cable as I could horizontaly to compensate for the lack of vertical depth and dry soil.

How deep did you bury it?

I started with a 100 foot roll and added from there and drove grounding rods as deep as I could and bonded them to the #4 cable.

How many "grounding rods"? How did you "bond them to the cable"?

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MisterB · October 2010

Re: Weird thing 2

The Cable is buried at around 1-2 foot depth and completly surrounds the house and goes 50 feet to the tower in the trench I dug for the tower cables. There are 4 grounding rods cut in half which gives me 3 1/2 grounding rod section at each of the 3 legs of the tower and 2 at each end of the house. I used standard grounding rod connectors and melted tin lead solder over the conncections with a plumbers torch to seal them against moisture and completley burried the ones by the house. The ones at the tower base are not sealed with solder and stick out above ground. I did this 20 years or so ago and if I did it again today, I wouldn't completly bury the ones by the house. And I should point out that my house is really just a glorified cabin and has 2 rooms and a sleeping loft so there is not much square footage.

One reason for doing it close to the house is that is where the soil is moist most of the time which is what you want for good conductivity with the grounding wire.

I have maybe 6 inches of soil before I start hiting small rocks and at 2+ feet I start hitting small boulders at some spots and there are others spots on my property where I can did to around 3 feet before I meet serious resistance. My house and Wind Generator Tower are both on the rockier areas. It was a serious project to do the foundation of the tower which involved diging 3 feet down vertically for each leg but the advantage was once done, the legs are set in concrete poured into solid rock and aren't going anywhere. I also set the grounding rods at the edge of the concrete pour which means they should touch concrete on on side and the earth on the other side of them. At the time I did this, there weren't any online forums to consult so I pretty much did it with the advice of a couple of local dealers and my own intuition. So far, so good, not one lighnting strike in almost 20 years of having the tower.

Weird thing 2

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