Overhead Power Lines Dangerous To Life and Property

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mbrooke

Batteries Included
Location
United States
Occupation
Technician
And again, folks may not have power :rolleyes::rolleyes::rolleyes::mad:


15 million Backup generators for every building in the north east is not practical IMO.
 

paulengr

Senior Member
Don't those elbows flash over internally when they are pulled out on equipment higher than 15kv?

No.

Early on there was a design defect that affected all of them. In cold weather the rubber would pull away internally and cause a partial discharge that led to some early failures that were region and manufacturer specific. Cooper has a full explanation on their web site. By now those are long gone out of service and the danger was only during severe cold weather, negative temperatures.

There was a case investigated by OSHA in which it appears they were working in a large vault and pulled one apart from activity in another part of the vault or that there was cable damage unknown/unseen at the time. Too many unknowns to say it was an elbow failure. Too many are out there though to say it’s a design issue. At this point it comes down to manufacturing defect or installation error.

As with ANY MV connection of course proper installation procedures are critical. With elbows the transition from cable to elbow particularly right at the end of the stud is a critical area. As voltage increases poor workmanship issues become more apparent. At 25 or 35 kV you are bordering on 69 kV and need to perform installation similar to 69 kV terminations. No short cuts. Deburring for instance is a necessity as is semicon if the instructions call for it. No nicks, perfectly straight cuts, that sort of thing. I don’t subscribe to much of their sales pitch but there is a company selling MV testing that repeatedly finds uneven cuts or nicks in semicon that trigger corona discharge and eventually tracking damage and termination failure. Good thing wells are screw in.

Up to 200 A you can get load break and non load break elbows. The 600 A are non load break only. What this means is that if a transformer is unloaded you can pull it just like any isolating switch. You will get a small, harmless visible arc that gets bigger with higher voltage. Nothing to get excited about. It’s just the magnetizing current. Load break elbows can actually ensure removal while energized but NOT under fault, just like say a cutout. However I don’t recommend them. The non load break types can require up to a limit of around 100 pounds to remove. That’s a lot compared to a cutout but not hard for most adult linemen or electricians. The load break types can require up to 250 pounds where you are trying to find ways for two or three large men or using equipment (truck) and lots of rigged ways to remove them which makes them not so user friendly. They go on/off easy the first few weeks but after six months or so they are really stuck on, both types. Some brands come with and recommend silicone oil based grease but this evaporated after a few months adding to the problem.
 

mbrooke

Batteries Included
Location
United States
Occupation
Technician
This info is Gold.

AS far as I'm concerned fewer types the better.

Open the network protector, de-load the trafo by doing so, pull on the elbos. I kind of like.
 

mikeames

Senior Member
Location
Germantown MD
Occupation
Teacher - Master Electrician - 2017 NEC
Economic prosperity has everything to do with it? The US is the richest country on earth, yet has one of the cheapest distro systems on earth. Many antiquated.

I think you are making the the false association that Economic prosperity means a country should be better in all ways and since you think underground is better then the more economically prosperous US should have Underground. You are disregarding choice. A millionaire can choose to drive a less expensive used car that requires normal maintenance even though they could afford a brand new car.

What I am saying is the US population is content with the current system given its costs. You can say 500,000 people are without power because of a storm. You can tell me all 300 million lost power for 6 months. I don't care the fact of the matter is the reliability of the electrical grid is acceptable to the people given the cost. If it wasn't then you would see the politicians and the general public talking about it daily. The major failures are often the result of lack of maintenance and stupid decisions made by people. Not the fact that powerlines are above ground. You see and hear more about health care and the world will end in 10 years (AOC) then the electrical grid. I am not saying its perfect and I am not saying it cant be improved for a fair low cost. I am saying its serves its purpose well given the cost and the public in general does not have an issue with its reliability.

You can have the opinion that it could be better, and frankly I agree it probably would be better on balance if it was all undergound but that grossly discounts the cost vs the gain. If people lost power like they lost cell service in the late 90s you would definitely see people support a more costly change. Instead what do you see. People switching over their cars to electric with full confidence they can charge at home. Peoples actions speak louder and their actions say the grid is reliable at an acceptable cost.

One area I would agree with underground utilities that you haven't mentioned is physical security. I am not sure I should say this but imagine a scenario where a small distributed group of people coordinated a simultaneous attack on substations across the country. Shooting insulators on transformers and and distribution lines simultaneously. You could feasibly take the grid down with a couple hundred people or less. I think that deserves more attention than thunderstorm outages. People expect them like they expect traffic jams. Nuisance, wasted time and energy but part of life. People don't expect and don't want a complete failure.
 

mikeames

Senior Member
Location
Germantown MD
Occupation
Teacher - Master Electrician - 2017 NEC
This video I think describes it best. Tornado strong enough to blow out windows, and yet the lights do not even dim.


We are talking past each other. Nobody denies that point. Your like a salesman.

"Look folks you too can have power that will survive the apocalypses
Yea, how much....
Only an extra hundred a month
No thanks......
But.... its better.......
Yea I am ok......
But others that don't make as much as you have this???
Great!
 

mbrooke

Batteries Included
Location
United States
Occupation
Technician
I think you are making the the false association that Economic prosperity means a country should be better in all ways and since you think underground is better then the more economically prosperous US should have Underground. You are disregarding choice. A millionaire can choose to drive a less expensive used car that requires normal maintenance even though they could afford a brand new car.

What I am saying is the US population is content with the current system given its costs. You can say 500,000 people are without power because of a storm. You can tell me all 300 million lost power for 6 months. I don't care the fact of the matter is the reliability of the electrical grid is acceptable to the people given the cost. If it wasn't then you would see the politicians and the general public talking about it daily. The major failures are often the result of lack of maintenance and stupid decisions made by people. Not the fact that powerlines are above ground. You see and hear more about health care and the world will end in 10 years (AOC) then the electrical grid. I am not saying its perfect and I am not saying it cant be improved for a fair low cost. I am saying its serves its purpose well given the cost and the public in general does not have an issue with its reliability.

You can have the opinion that it could be better, and frankly I agree it probably would be better on balance if it was all undergound but that grossly discounts the cost vs the gain. If people lost power like they lost cell service in the late 90s you would definitely see people support a more costly change. Instead what do you see. People switching over their cars to electric with full confidence they can charge at home. Peoples actions speak louder and their actions say the grid is reliable at an acceptable cost.

One area I would agree with underground utilities that you haven't mentioned is physical security. I am not sure I should say this but imagine a scenario where a small distributed group of people coordinated a simultaneous attack on substations across the country. Shooting insulators on transformers and and distribution lines simultaneously. You could feasibly take the grid down with a couple hundred people or less. I think that deserves more attention than thunderstorm outages. People expect them like they expect traffic jams. Nuisance, wasted time and energy but part of life. People don't expect and don't want a complete failure.

Simpler, a country with less money has figured out how to make undergrounding cheaper. I still stand by my comments about the NEC in comparison. A system built to BS7671 will often have many code violations compared to NFPA-70. Yet despite less copper and raw material, the system is just as safe, if not more safe. The lights still come on, but at less cost.

You are correct about choice, however more and more people are asking for underground lines. "It doesn't make sense to rebuild infrastructure after every storm" They are talking about it daily in some places.

500,000 customers in just one state like MA, RI, CT, NY or NJ for a few days is not uncommon. That type of reliability is not acceptable. The cause of these outages is not lack or maintenance or stupidity, though yes they do contribute, but rather trees and lightning. To cut down every tree in NY, MA, NH and CT is not practical.

The electric grid is just one small sector being effected by climate change. While people talk about slowing climate change, its to late to reverse it. Humanity at this point literally needs to build stronger, go underground and desalinate water in order to deal with the irreversible outcome of a 1.2*F global temperature rise IMO.


Regarding physical attack it happens all the time. Thats another subject the FBI busts people shooting at equipment, loosening bolts and stealing copper ground wire all the time. But that is a topic for another thread.
 

mbrooke

Batteries Included
Location
United States
Occupation
Technician
We are talking past each other. Nobody denies that point. Your like a salesman.

"Look folks you too can have power that will survive the apocalypses
Yea, how much....
Only an extra hundred a month
No thanks......
But.... its better.......
Yea I am ok......
But others that don't make as much as you have this???
Great!


Ok, that is good to know then. That at least we can agree on this :)
 

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
So as a rebuttal in hopes of addressing the root barrier I yet again pitch this question: How is it that lesser economically prosperious countires have maanged to underground 95% of their distro system?
Please provide a link to the report or table indicating how much of the distro system is underground per country. I'm doubting many, if any, are at 95%. Germany is about the best I could find, with 87% of low voltage underground. Tokyo, on the other hand, is just 7%. And you still didn't answer a previous poster showing that the cost to the end user could be about $400/month for 40 years. Which is just about the lifetime for underground cable.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
Please provide a link to the report or table indicating how much of the distro system is underground per country. I'm doubting many, if any, are at 95%. Germany is about the best I could find, with 87% of low voltage underground. Tokyo, on the other hand, is just 7%. And you still didn't answer a previous poster showing that the cost to the end user could be about $400/month for 40 years. Which is just about the lifetime for underground cable.
After 40 years you could just replace it all again and spend $400 a month of other people's money for another 40 years.
 

mbrooke

Batteries Included
Location
United States
Occupation
Technician
Please provide a link to the report or table indicating how much of the distro system is underground per country. I'm doubting many, if any, are at 95%. Germany is about the best I could find, with 87% of low voltage underground. Tokyo, on the other hand, is just 7%. And you still didn't answer a previous poster showing that the cost to the end user could be about $400/month for 40 years. Which is just about the lifetime for underground cable.

Really? Wiki?

MV is a lot higher.

I don't want to dig through my collection of archives and studies.
 

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
Really? Wiki?

MV is a lot higher.

I don't want to dig through my collection of archives and studies.
If you're too lazy to dig, I don't need to offer anything else. We can provisionally conclude your claim is bunk.

MV is lower, at 73%. But hey, it's Wiki, so let's pretend the sources in the article are all crap too.
 

mbrooke

Batteries Included
Location
United States
Occupation
Technician
If you're too lazy to dig, I don't need to offer anything else. We can provisionally conclude your claim is bunk.

MV is lower, at 73%. But hey, it's Wiki, so let's pretend the sources in the article are all crap too.


Conflating laziness with valominious information does not make one lazy.

At this point, have I ever made a claim that has ever proven to be bunk?
 

Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
No.

Early on there was a design defect that affected all of them. In cold weather the rubber would pull away internally and cause a partial discharge that led to some early failures that were region and manufacturer specific. Cooper has a full explanation on their web site. By now those are long gone out of service and the danger was only during severe cold weather, negative temperatures.

There was a case investigated by OSHA in which it appears they were working in a large vault and pulled one apart from activity in another part of the vault or that there was cable damage unknown/unseen at the time. Too many unknowns to say it was an elbow failure. Too many are out there though to say it’s a design issue. At this point it comes down to manufacturing defect or installation error.

As with ANY MV connection of course proper installation procedures are critical. With elbows the transition from cable to elbow particularly right at the end of the stud is a critical area. As voltage increases poor workmanship issues become more apparent. At 25 or 35 kV you are bordering on 69 kV and need to perform installation similar to 69 kV terminations. No short cuts. Deburring for instance is a necessity as is semicon if the instructions call for it. No nicks, perfectly straight cuts, that sort of thing. I don’t subscribe to much of their sales pitch but there is a company selling MV testing that repeatedly finds uneven cuts or nicks in semicon that trigger corona discharge and eventually tracking damage and termination failure. Good thing wells are screw in.

Up to 200 A you can get load break and non load break elbows. The 600 A are non load break only. What this means is that if a transformer is unloaded you can pull it just like any isolating switch. You will get a small, harmless visible arc that gets bigger with higher voltage. Nothing to get excited about. It’s just the magnetizing current. Load break elbows can actually ensure removal while energized but NOT under fault, just like say a cutout. However I don’t recommend them. The non load break types can require up to a limit of around 100 pounds to remove. That’s a lot compared to a cutout but not hard for most adult linemen or electricians. The load break types can require up to 250 pounds where you are trying to find ways for two or three large men or using equipment (truck) and lots of rigged ways to remove them which makes them not so user friendly. They go on/off easy the first few weeks but after six months or so they are really stuck on, both types. Some brands come with and recommend silicone oil based grease but this evaporated after a few months adding to the problem.
Partial vacuum flashover is still a real danger in cold (under 30 degrees) lightly loaded lines above 10kV.
generally not an issue at all for 7200V lines and below.
It’s the reason some cold regions use a type of heating blanket to warm the elbow before pulling it.

Manufacturers are trying bushings, rings, etc and different things to solve it.


 

romex jockey

Senior Member
Location
Vermont
well this is interesting......we've an aging and ailing infrastructure, some of which is assuming foreign ownership........we've climatic changes that obviously have their effects......and we've juxtaposed the cost efficacy of it being less vulnerable.

I suppose we could also throw in all the PV plans out there too, if they had a shot at reconfiguration i'm sure they opine for their benefit ~RJ~
 

kwired

Electron manager
Location
NE Nebraska
After 40 years you could just replace it all again and spend $400 a month of other people's money for another 40 years.
You do have to figure that many more recent installs pulled conductors/cables through raceways with the intention that when replacement becomes necessary you hopefully can pull replacement through the raceway and not have to excavate the entire run again which should save some cost at replacement time.
 

Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
You do have to figure that many more recent installs pulled conductors/cables through raceways with the intention that when replacement becomes necessary you hopefully can pull replacement through the raceway and not have to excavate the entire run again which should save some cost at replacement time.
Hopefully being the key word..

you know where an additional circuit is going to be needed or where potential housing developments or industrial will be in 10 or 20 years?
 

paulengr

Senior Member
That would be ignoring tropical storm Irene, the 2011 October snow storm, the 2013 snow storm, Hurricane Sandy, tropical storm Iasis, two dozen wind/rain events, and several ice storms that between New Jersey, New York State and New England have on average have left 3 million customers without power for 7 days.

I understand I'm challenging patriotic exceptionalism, however, the facts are becoming rather compelling.
If you look on a map of the United States, two states "stick out" into the Atlantic Ocean. The one that sticks out the farthest unsurprisingly is...Florida. And the second is North Carolina. In fact you see that big bulge that sticks way out into the Atlantic in North Carolina? That's where I live. Every utility around here gets "stress tested" every year in the fall. Some storms are more severe than others but we seem to get either a storm making land fall or at least passing close by every year.

Every utility has a "design book" for power lines. Most have about 50 different details drawings that cover just about any possibility. If you know the right people and you ask, you can easily get a copy. In "flat land" like where I live, that's really all you need as a contractor to build a power line. The exception is out in the mountains where "simple" rules don't apply and they actually have to engineer their power lines. There are 3 design codes: RUS (which is really a premade "design book"), NESC (very simple), and ASCE with all the "bells and whistles". Taking NESC to task the area I live in is designated an "extreme wind" zone. But it also states to ignore extreme wind if the pole is under 70 feet and it assumes that all pole lines are in residential areas with some trees and single story buildings. ASCE is the most general and flexible design code for pole designs and includes modifiers for terrain and doesn't arbitrarily ignore "short" poles.

So given this information, it should not surprise you that I have gotten plenty of chances to see downed power lines first hand. What's interesting is that in areas where you can observe multiple utilities such as Duke and a local EMC, you can easily tell which ones are designed for extreme wind conditions and which ones aren't. With the utilities that are deficient, you will see an open field and EVERY pole is on the ground. If it was just one or two poles, or even just one or two pole lines, it would point to some installation issues. But when it's nearly every exposed pole line it becomes obvious that there are serious design defects. For instance in this area using RUS is a very bad idea, and even using NESC as a design standard is questionable at best.

So it's my experience that downed lines happen because of poor design practices. Hurricanes are routine, not random acts of nature. It's one thing to build structures in say New Jersey where they see a hurricane once every 20 years. It's quite different where I live. And also just to reinforce some things, I have friends who live in the Egg Harbor Township area in New Jersey, less than 10 miles from Atlantic City. During Sandy, they never even lost power.
 
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