Ahhhh Colorado.....

delta T

Here is the forecast for my area for the next few days.....

Wed: High 80, Low 30 Red flag warning for high wild fire potential in effect
Thurs: High 39, Low 16 2" of snow
Fri: High 54, Low 26 Sunny
Sat: High 68 partly cloudy

Like they say, if you don't like the weather in Colorado, wait 5 minutes....

Happy start of heating season all!!

Intplm.

Yikes! And I thought New England was tough.

JUGHNE

Do they shut off your power for Red Flag Fire warning days??
Or is CO not as advanced as CA....never happens in NE...but we are quite a backward lot here.

SeanBeans

56 degree delta T forecasted today in Denver @delta T

Sal Santamaura

JUGHNE said:

Do they shut off your power for Red Flag Fire warning days??...

Some day, when the transmission lines have all been moved underground, that will no longer be necessary. It'll make the landscape look a lot nicer too.

JUGHNE

That is a very major undertaking with 245,000 to 300,000 volts and miles involved.

ChrisJ

JUGHNE said:

That is a very major undertaking with 245,000 to 300,000 volts and miles involved.

Many are even 500KV no?

I have no idea how you run such things underground.

Solid_Fuel_Man

As a long time master electrician in the far NE I'll say one thing about underground power of any kind:

Failure in <30 years.
I have lots of pics and overtime to prove it.

End of statement.

ChrisJ

> @Solid_Fuel_Man said:
> As a long time master electrician in the far NE I'll say one thing about underground power of any kind:
>
> Failure in <30 years.
> I have lots of pics and overtime to prove it.
>
> End of statement.

What is usually the cause?

JakeCK

> @ChrisJ said:
> > @Solid_Fuel_Man said:
> > As a long time master electrician in the far NE I'll say one thing about underground power of any kind:
> >
> > Failure in <30 years.
> > I have lots of pics and overtime to prove it.
> >
> > End of statement.
>
> What is usually the cause?

I've always heard that lightning, believe it or not, does more damage to underground power lines then above ground.

JUGHNE

Lighting is looking for a good ground. There is a well grounded conductor in every buried system. That insulation does not stand a chance to stop it. Lighting just sees it and says get out of my way, I'm coming thru.

I did some UG work in the lowest "high" voltage there is, just 2400 phase to phase. Some old install had just plain insulation rated for maybe 6k, it was in a steel conduit and failed. I had to upgrade it.
In my mind all AC power wants to get back to the source and that is thru return conductors but also thru the earth.
Being UG and in very close proximity to earth the insulation is eventually compromised enough to break down. The electrons want out to get back to the source via earth.

IIRC, even for just 7200 VAC the conductors had insulation, some type of semiconductor jacket and grounded bleed wire sheathing. The end termination required special attention, perhaps penciling the insulation back and special taping insulation.
This was to bleed off the corona charge built up on the insulated cable itself. Most of the time the grounded mesh was also used for the neutral return.
There is a lot of high tech engineering to the UG route.

The higher the voltage the more containment is needed.
So far air separation with wires hanging on maybe 6-10' of super insulated hangers seems to work.

Solid_Fuel_Man

Yes @JUGHNE !

The semiconductor layer slowly bleeds back the high impedance through the insulation to the braided ground. Its expensive, less efficient, and blows up literally when there is a fault. I'm not well versed in what the tech is for high voltage UG is though.

Also capacitive coupling comes more into effect with conductors in the ground, more so than in the air. It is a very common misconception that UG wires will last forever and are safer/more efficient.

@ChrisJ the reason I see that low voltage (480 volts or less) cables/conductors fail is water. All conduit fills with water, and freeze-thaw cycles kills the insulation, then bad stuff happens. Higher voltages (2400 and up) fails sooner due to insulation stress and water again.

JUGHNE

Solid_Fuel_Man said:

Yes @JUGHNE !



The semiconductor layer slowly bleeds back the high impedance through the insulation to the braided ground. Its expensive, less efficient, and blows up literally when there is a fault. I'm not well versed in what the tech is for high voltage UG is though.



Also capacitive coupling comes more into effect with conductors in the ground, more so than in the air. It is a very common misconception that UG wires will last forever and are safer/more efficient.



@ChrisJ the reason I see that low voltage (480 volts or less) cables/conductors fail is water. All conduit fills with water, and freeze-thaw cycles kills the insulation, then bad stuff happens. Higher voltages (2400 and up) fails sooner due to insulation stress and water again.

\
So what is the highest voltage you have seen UG?

Zman

1.21 Gigawatt

Zman

Serious though, in my area it is pretty unusual to see more than 14.4 underground. Utility engineers begin rolling there eyes when you ask about putting the big stuff underground. I think heat and safety become the driving factors.

Sal Santamaura

JUGHNE said:

That is a very major undertaking with 245,000 to 300,000 volts and miles involved.

ChrisJ said:

Many are even 500KV no?

I have no idea how you run such things underground.

There's one critical element in such a project: Money. Lots of money. The rights-of-way are already there.

Solid_Fuel_Man

I commonly see 7200 volts UG to padmount transformers we put in. That is our local distribution voltage for in town. 12,470 is country distribution voltage, but dont have any padmounts there that I have worked on. I am not, however, a utility worker. So my knowledge is limited on high voltage UG.

Sal Santamaura

Sal Santamaura said:

There's one critical element in such a project: Money. Lots of money. The rights-of-way are already there.

A transmission project through New Hampshire, the Northern Pass, which was to have 239 miles of 300kV DC and 40 miles of 345 kV AC line, was killed in July by that state's Supreme Court after many years of citizen opposition and a lengthy review process. It was estimated to cost $1.6 billion and would deliver 1000 MW to southern New England.

https://www.transmissionhub.com/articles/transprojects/northern-pass-transmission-project

Had those proposing the link agreed to underground it all the way, DOE estimated (in 2015) project cost would double to $2.2 billion.

https://www.vnews.com/Archives/2015/07/NorthernPass-vn-cm-072215

Meanwhile, two other projects designed to carry energy from Canada to southern New England are moving along, both intended to be completely underground. A third, 146 miles longer than Northern Pass, also completely underground, will bring 1000 MW to the New York metro area and is estimated at $2.2 billion.

I'm not familiar with the modern technology used for these lines, but, given their status, am relatively confident that whatever challenges undergrounding them presents have been overcome. Just bring dollars.

Sal Santamaura

Sal Santamaura said:

... Just bring dollars.

A new article that quantifies exactly how many dollars:

https://www.usatoday.com/story/news/nation/2019/10/11/bury-california-power-lines-wildfire-blackout-fix-unlikely-work/3946935002/

Intplm.

Hey there @delta T . Did I see a recent weather forecast in your area that said it was 83 deg. during the day then dropped to 18 deg at night ? HA!? What ?

delta T

@Intplm. not quite, it was 82 on Wednesday for the high, then dropped to 16 for the low on Thursday Night. Friday was in the high 50s, its in the 70s now. Colorado is crazy sometimes....

Solid_Fuel_Man

Scorched air will work. 😁

Sal Santamaura

Sal Santamaura said:

Sal Santamaura said:

... Just bring dollars.

A new article that quantifies exactly how many dollars:

https://www.usatoday.com/story/news/nation/2019/10/11/bury-california-power-lines-wildfire-blackout-fix-unlikely-work/3946935002/

Perhaps, at least in the arid West, it might be worth the cost:

https://news.yahoo.com/punishing-winds-whipped-california-fires-055147838.html