Blooey!!

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rattus

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Thor threw a thunderbolt directly at a transformer down the alley from me Friday AM. Blew up a lightning arrestor, zapped my TV, modem, and garage door safety system. Power was off for a couple of hours.

The remains of the arrestor were scattered in the alley--chunks of porcelain, carbon, and brass. It appears that this thing consisted of an air gap and a resistor molded into a porcelain enclosure. Anyone know the details of these devices?
 
air gap

air gap

is a spark gap to limit the voltage, just as a neon bulb/MOV/Zener diode in series with a resistor gives a constant voltage across it.

I guess if this arrestor were large enough (but see "trees" below) it could absorb all the energy dumped in a lightning strike and live to tell about it.

You know why trees explode when hit by lightning? The sap is instantly vaporized and turns to steam.
And how 'bout one of these in your living room?
http://everything2.com/title/fulgurite

If you know the volts, amps, and time duration, the horsepower of a single strike should be easy to calculate. From there someone can probably convert this energy into a pounds-of-TNT equivalent.

Where is that sliderule?
 
Once the voltage increases enough to jump the gap it provides annother path to try to divert the lightning to ground or up to the sky whichever theory you believe in. He was a very brave lightning arrestor. Blown to pieces in the line of duty.
 
Lxnxjxhx said:
is a spark gap to limit the voltage, just as a neon bulb/MOV/Zener diode in series with a resistor gives a constant voltage across it.

If you know the volts, amps, and time duration, the horsepower of a single strike should be easy to calculate. From there someone can probably convert this energy into a pounds-of-TNT equivalent.

Where is that sliderule?
Click to expand...

Next time we have a thunderstorm I will put on my hooks and take my Amprobe, voltmeter, and stopwatch up the pole to measure these values. Yes, a sliderule is in order since a calculator might get zapped.'

On second thought, I have only climbed one pole in my life, and I made a fool of myself then, so I will leave this exercise to someone younger.
 
Every manufacturer has a different style of voodoo in their pole top arrestors, but they basically all have an air gap and semi-conducting material.
 
Lxnxjxhx said:
You know why trees explode when hit by lightning? The sap is instantly vaporized and turns to steam.
Click to expand...
Popcorn pops because of water vaporizing, too.
 
I didn't think about the sliderule/calculator thing; good idea, no use in risking my

I didn't think about the sliderule/calculator thing; good idea, no use in risking my

calculator.

Here's how to run your house on lightning.

1 BTU can raise one pound of water one degree Fahrenheit.

You make this way huge, thermally-insulated sphere full of a semi-conducting liquid which is yet to be designed, which attracts and then totally absorbs each strike.
You use the stored heat to run all kinds of Carnot-cycle engines.

Getting a permit might be a bear. Maybe if you paint the sphere light blue it will blend in a little better, for the inspection.

Hey, I've seen Christmas displays that looked worse.
 
Crossarms:

Crossarms:

Why are some crossarm braces made of wood? Looks like the lightning broke one behind my house?
 
rattus said:
Why are some crossarm braces made of wood? Looks like the lightning broke one behind my house?
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They're made out of a variety of materials all over the world, but it comes down to what is plentiful, locally available, and economic to manufacture and install. Most of the heftier distribution poles that have gone in around here lately have been concrete or steel. Not so many tall trees left in the east. They have to be imported from other countries like Oregon. :smile:
 
Just Wondering

Just Wondering

Rattus, are you going to show some pic's of the new install ? ?
 
rattus said:
Why are some crossarm braces made of wood? Looks like the lightning broke one behind my house?
Click to expand...

The utility should come out and fix this before it does break and cause an outage. I hate seeing this happen. Why did they not replace the broken crossarm when they were out there replacing the arrestor and probably the transformer? Instead they will be out there when it fails replacing it at 2 am on overtime.

On another note, I am a fan of fiberglass crossarms. They have insulating properties like wood, they are much lighter than wood, and they are stronger than wood. Price is coming down to be more competitive too.
 
wirenut1980 said:
The utility should come out and fix this before it does break and cause an outage. I hate seeing this happen. Why did they not replace the broken crossarm when they were out there replacing the arrestor and probably the transformer? Instead they will be out there when it fails replacing it at 2 am on overtime.
Click to expand...

They reconnected with a long pole in the early AM. A day or so later, they sent a bucket truck to replace the damaged parts.

Telephone man came out Saturday to replace my modem--double time, but I didn't have to pay anything.
 
I used to live in Virginia and there was a power pole righty outside my house with a transformer on it. One evening (after dark) during some high wind, there was a loud buzzing sound that caught my attention. About the time I got to the window and looked up at the transformer, it produced a bright flash comparable to an arc welder that briefly lit up the entire neighborhood (and hurt my poor little eyes). Power went off for about 10 seconds, then everything returned to completely normal. I called the POCO and reported the incident because I figured they'd want to know about the transformer. When I got done describing the incident to the operator that answered the phone, she said something like "Wait a minute...the power is back on now?" I said yes it is but I thought you would still want to take a look at that transformer. She said they would send somebody out to look at it later, but was obviously miffed at the idiot that called to report his electricity was working fine.
 
drbond24 said:
About the time I got to the window and looked up at the transformer, it produced a bright flash comparable to an arc welder that briefly lit up the entire neighborhood (and hurt my poor little eyes). Power went off for about 10 seconds, then everything returned to completely normal.
Click to expand...
Sounds like a recloser doing its job.
 
drbond24 said:
I agree. It was the bright flash of light coming from the transformer that I was concerned about.
Click to expand...


Sounds like a momentary contact from a tree limb or other debris. As long as the fault isn't sustained, usually no major harm results. As Larry said, there is a recloser on the line that trips during a fault, pauses several seconds, then as its name implies, recloses to see if the fault has cleared. If it has, it stays closed and resets its internal counter (which counts reclosing attempts.)

If the fault was sustained, it would have reclosed up to two more times then locked open to alert the POCO where the fault is.

Here's a link to a recloser being tested:
 
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