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Fatal Attraction


mgbinspect
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Well, here's an interesting one for the brain trust:

I see this about once a year: It's a rural property. About 20 feet from the back porch is a utility pole with a step-down transformer and a service drop from the transformer to the house. The pole is probably 21 feet tall +.-. Primary and neutrals lines of bare twisted copper run the length of the property (probably 100 yards) at an average of 17 - 20 feet off the ground.

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I gave my son a shout (he used to work for the local power company) and he said the primary is probably pushing 7600 volts - standard procedure to be bare wire. And, my son readily admits that people have been killed by leaning something conductive up against that wire, but the power company probably won't change it out for a covered wire.

I plan to include a BIG warning about the potential of accidental electrocution since they have kids.

Would you?

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I've never seen bare transmisssion lines. Most utilities would fix that here, and some would go so far as to move the transformer. I had a client that built an addition and the overhead entrance was actually stretched tight over the new overhang. When I called to request the entrance be moved so I could install soffit and fascia, they where there the next day and replaced the old over head with over 200' of new triplex, free of charge.

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I've never seen bare transmisssion lines. Most utilities would fix that here, and some would go so far as to move the transformer. I had a client that built an addition and the overhead entrance was actually stretched tight over the new overhang. When I called to request the entrance be moved so I could install soffit and fascia, they where there the next day and replaced the old over head with over 200' of new triplex, free of charge.

Of course, all transmission lines crossing the country from tower to tower are bare conductors. But, only in rural areas will they be seen feeding a house. Then, just the drop will be covered.

That's why I called my son. He was a groundsman for several years in the Outer Banks and on the mainland. He said the only time they used covered wire was in very special cases where it was running through the woods with a high probability of shorting out.

Last time I suggested that the home owner send a certified letter to the power company laying out the concerns. That way, the power company's attorneys will have to decide whether they want total liability for not eliminating the potential disaster.

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Well, here's an interesting one for the brain trust:

I see this about once a year: It's a rural property. About 20 feet from the back porch is a utility pole with a step-down transformer and a service drop from the transformer to the house. The pole is probably 21 feet tall +.-. Primary and neutrals lines of bare twisted copper run the length of the property (probably 100 yards) at an average of 17 - 20 feet off the ground.

I gave my son a shout (he used to work for the local power company) and he said the primary is probably pushing 7600 volts - standard procedure to be bare wire. And, my son readily admits that people have been killed by leaning something conductive up against that wire, but the power company probably won't change it out for a covered wire.

I plan to include a BIG warning about the potential of accidental electrocution since they have kids.

Would you?

Photos in a bit.

No, I wouldn't bother. It's beyond the scope of the inspection.

What your son said. In all my years, I've never seen a distribution line insulated.

2400 & 7600 are older common voltages for distribution lines. The trend now is towards 13.8 KV which is usually adjusted to just over 14 KV by the utilities to better tolerate voltage drops over long distances. Whether it's 7.6 or 13.8 really doesn't matter, you're toast either way if you bridge the gap between it and the earth. When I was in my single digits, I tossed a kite string over the distribution line in our front yard. I don't know why I did it, but I happen to let go of it just in time to see it vanish into a line of sparks and smoke. It likely made a loud noise because the neighbor came running out his front door across the street. I was badly hard-of-hearing at that time and didn't hear anything.

Marc

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Well, here's an interesting one for the brain trust:

I see this about once a year: It's a rural property. About 20 feet from the back porch is a utility pole with a step-down transformer and a service drop from the transformer to the house. The pole is probably 21 feet tall +.-. Primary and neutrals lines of bare twisted copper run the length of the property (probably 100 yards) at an average of 17 - 20 feet off the ground.

I gave my son a shout (he used to work for the local power company) and he said the primary is probably pushing 7600 volts - standard procedure to be bare wire. And, my son readily admits that people have been killed by leaning something conductive up against that wire, but the power company probably won't change it out for a covered wire.

I plan to include a BIG warning about the potential of accidental electrocution since they have kids.

Would you?

Photos in a bit.

No, I wouldn't bother. It's beyond the scope of the inspection.

What your son said. In all my years, I've never seen a distribution line insulated.

2400 & 7600 are older common voltages for distribution lines. The trend now is towards 13.8 KV which is usually adjusted to just over 14 KV by the utilities to better tolerate voltage drops over long distances. Whether it's 7.6 or 13.8 really doesn't matter, you're toast either way if you bridge the gap between it and the earth. When I was in my single digits, I tossed a kite string over the distribution line in our front yard. I don't know why I did it, but I happen to let go of it just in time to see it vanish into a line of sparks and smoke. It likely made a loud noise because the neighbor came running out his front door across the street. I was badly hard-of-hearing at that time and didn't hear anything.

Marc

You know what I found shocking (no pun intended)? I was watching a show in Discovery Channel about the transmission lines that cross the country and all that goes in to maintaining them. (I used to work part-time at our local airport fueling aircraft. One of the regular customers was the helo that hovered over the lines with a thermal imaging camara to see and document the insulators that were begining to fail, so they can be replaced.) But, the one thing they said in that show that I found amazing was that, if a good ground got within 11' - 8" of the highest voltage lines out there, the current would jump that arc! Now that's freaky.

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You know what I found shocking (no pun intended)? I was watching a show in Discovery Channel about the transmission lines that cross the country and all that goes in to maintaining them. (I used to work part-time at our local airport fueling aircraft. One of the regular customers was the helo that hovered over the lines with a thermal imaging camara to see and document the insulators that were begining to fail, so they can be replaced.) But, the one thing they said in that show that I found amazing was that, if a good ground got within 11' - 8" of the highest voltage lines out there, the current would jump that arc! Now that's freaky.

The utilities always strive to avoid any sharp or pointed surfaces on the conductors of transmission lines. Electric charges tend to concentrate at those locations and that allows them to 'jump' longer distances. That why lightning rods are pointed at the top, it makes them more attractive to lightning strikes.

Marc

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In your warning you might mention that it isn't necessary for someone to actually touch the lines in order to be zapped. They need only come close.

- Jim Katen, Oregon

That's a good point, Jim, I had not thought to mention the potential for arcing in the report.

I just texted my son and asked him what he's actually witnessed with 7600 Volts. He texted back, "I've seen some crazy sh*t, I'd say maybe six feet. But it all comes down to load. Voltage matters little. Load is everything. A single house on a single tap line, the load is gonna be minimal. A tap line with a few houses like what you describe will have more load. I've watched 100,000 volts explode."

I remember that when he worked in the outer banks, he said when a buried line failed at the beach, they'd just dig along the line, where they suspected the failure was, until the sand bagan to become glass - bingo!

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I just texted my son and asked him what he's actually witnessed with 7600 Volts. He texted back, "I've seen some crazy sh*t, I'd say maybe six feet. But it all comes down to load. Voltage matters little. Load is everything. A single house on a single tap line, the load is gonna be minimal. A tap line with a few houses like what you describe will have more load. I've watched 100,000 volts explode."

I don't know why your son said load was the factor in arcing distance on medium and high voltage power lines. It's the voltage level and the presence or absence of sharp or pointed conductor surfaces that matters. Loading, when within the line's specs, has nothing to do with arcing distance.

Show your son that 2nd photo in your OP. Ask him if he thinks that could be 2400 V. To me, the line on top seems to me to be the hot wire and the insulator securing it to the top of the pole is too small for the higher voltages.

Marc

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I just texted my son and asked him what he's actually witnessed with 7600 Volts. He texted back, "I've seen some crazy sh*t, I'd say maybe six feet. But it all comes down to load. Voltage matters little. Load is everything. A single house on a single tap line, the load is gonna be minimal. A tap line with a few houses like what you describe will have more load. I've watched 100,000 volts explode."

I don't know why your son said load was the factor in arcing distance on medium and high voltage power lines. It's the voltage level and the presence or absence of sharp or pointed conductor surfaces that matters. Loading, when within the line's specs, has nothing to do with arcing distance.

Show your son that 2nd photo in your OP. Ask him if he thinks that could be 2400 V. To me, the line on top seems to me to be the hot wire and the insulator securing it to the top of the pole is too small for the higher voltages.

Marc

Hey Marc,

My son, Keith, was fortunate to land such a fine job right out of the Navy. He's gone on to run an airport ramp, which is more to his liking, since he worked a Catapult on the USS John C Stennis for four years. That's where I worked part time and worked toward my pilot's license (thanks only to substantially reduced flight time and fuel charges - membership has its privileges).

Of course anything he understands about electrict is the result of a few apprentice classes, personal field experience and shop talk. So, he can very well be wrong - a bit of hear-say and superstition.

I asked for his thoughts sight unseen, so you probably know better what we're looking at than he does.. I can only tell you that transmission line continues on to other properties.

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