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Electrical Connection: Grounding case history
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This case history is about a grounding system I installed. A woman asked me about her whole house surge protector ("Meter Treater"). I read the contract's fine print, which basically exempted the installer (the utility) from any liability or warranty claims whatsoever. |
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About the author:
Perhaps you'll agree I have some credentials for what comes next. |
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Click on the thumbnails to see the images full-sized. |
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The catch was the home had to comply with the National Electrical Code, and very, very few homes ever do (mine does, but did not when I bought it). I fixed one severe violation of Article 250 (her water pipes weren't bonded to the electrical system--she lives in a duplex and her system was bonded to her neighbor's pipes and the two systems weren't bonded together). I then installed a very fine supplemental grounding system, using buried #4 wire and driven rods. OK, I know your eyes are probably glazing over at this point, but bear with me. Her home sits between two trees. In a recent lightning storm, these trees were hit badly (as the photos show). One tree got so hot at the point of the lightning strike that the leaves were instantly desiccated. This, and other evidence, shows she had a huge electrical field present at the back of her home. In the photos, you can see where an electrical charge blackened the outer surfaces of the grounding electrode conductor and the top of one ground rod. You can also see where energy discolored gravel. On the other side of the fence, her hot tub was destroyed. Inside the house, nothing was damaged, as the Meter Treater was able to shunt the electrical surge to ground. If not for this grounding system, her house may well have burned down. Yet, I installed this system for about $30 in parts. If you have not hired an electrician to beef up your home's grounding system, I urge you to do so. It's a cheap insurance policy. If you are an electrician, follow the National Electrical Code, Article 250, to the letter. Get a copy of IEEE-142, and read it carefully. |
Photo 1: North tree. Notice the damage from the lightning blast. This part of the tree is sitting directly on power lines. |
Photo 2: North tree. A little closer up. The heat was so intense, it dessicated the leaves near the point of the blast. The leaves are still green about 12 feet from the blast. |
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Photo 3: North tree. Here, you can see how massive the damage was. Remember, this is
only one of the trees that got hit. Look at how large it is, compared to the fence. |
| The tree is lying on top of power lines. Notice how green it is from this view. That's because you're not seeing the blast zone. This was a healthy tree that got split by lightning and nearly caught fire. If not for the heavy rain, it probably would have ignited. The rain, during this storm, was so heavy that visibility was often as little as three feet. |
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| OK, you get a break from looking at the same tree. Here, you can see the north tree to the left, and you can see the south tree to the right. The point of this photo is to show you the south end of the lightning zone. Look how large of an area the electric field covered! Her electric service entrance is almost mid-center of the East-West axis. This south tree also had significant damage. |
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| Now we get to the meat of the thing. If you look closely, you can see black marks on the #4 conductor. It is buried in gravel and sand, and sat in water during this storm. The part that sticks up had a higher resistance to earth than the buried part, so it wasn't able to discharge to earth. Notice the top of the electrode--black! |
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| Here's another photo of that electrode. In both of this photo and the one above, you can see discoloration in the formerly white gravel leading to the fence. The hot tub on the other side was fried. You can see some vegetation got zapped, too. These photos were all taken a few days after the storm. Oddly, the gravel under the fence has some of the color of the fence now--you can see how current flow under the fence damaged the fence. We think it vaporized paint and impregnated the particles into the rock. The rock was added after the fence was painted, so this isn't from overpaint. |
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What's the moral of this story? Well, here are the principles it demonstrates:
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Lightning protection Websites
- http://www.harger.com.
Harger Lightning Protection. Since its inception in 1960, Harger has
become a leader in the lightning protection industry. Founded on the
principles of honesty, integrity, and technical expertise, Harger has been
able to provide lightning protection solutions for many satisfied customers.
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http://www.kuefler-lightning.com. Kuefler Lightning Protection Systems, Inc. Designing layouts for lightning protection systems with a complete line of top quality lightning rod parts and information on lighting protection.
- http://www.protectiongroup.com.
The Protection Technology Group. A leader in signal integrity
solutions that protect systems and equipment from lighting and power
anomalies.
| Need to solve harmonics problems? Take this comprehensive, inexpensive harmonics causes and cures course. |
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Electrical Resources |
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Miscellaneous
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| IEEE Kansas City Section and Society Chapter Meetings: | ||
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Need to pass an electrical exam?So, you need a state license and must pass a code exam to get it. You can choose between taking the test and hoping for the best (the usual approach), or preparing for the exam and passing with flying colors the first time. Let’s assume you don’t like to waste time and money, and don’t want to wait six months or longer for a retest. That assumption means you must know how to prepare for the exam. To prepare for electrical code exams, click here. Step 1: Buy and review a current code book. You can’t know the code unless you read it.
Step 2: Study
Step 3: Practice.
Passing a code exam is tough for most folks, but easy for some. Follow these tips and you’ll be in that second group. | ||