Entergy New Orleans Transmission Tower Collapse and Resulting Blackout 6

[Mbrooke]

A major transmission tower structure appears to have collapsed into the Mississippi river blacking out all of New Orleans/Orleans Parish:

https://imgur.com/mLEWQDZ

Reports indicate this to have been a vital power path-

https://kpel965.com/major-entergy-transmission-tower-collapses-into-river/

https://www.wafb.com/2021/08/30/no-power-orleans-parish-due-catastrophic-damage/

A statement from Entergy says they lost 8 transmission lines which resulted in an energy imbalance causing local generation to trip off line:

https://www.entergynewsroom.com/sto...334907&utm_campaign=power_outages/restoration

Any more info welcome, as well as thoughts on what may have gone wrong and how to prevent this in the future.

As of right now I scouring the net for any more updates or information.

Edit: I am now hearing that possibly all generating stations on South East Louisiana have come off line. No power generation in that entire portion of the state.

 

[waross]

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[FacEngrPE]

I guess this is the other end of the crossing being discussed above?
Entergy to blow up a Harahan transmission tower that was damaged in Ida
New Orleans Electrical Transmission Line Failure Drone

I would not think the lack of paint is a huge issue the tower is too young. If the tower is constructed using weathering steel (ASTM A588 or ASTM 604 also known as COR-TEN) paint is optional, usually applied for cosmetic reasons. Many monopoles in my area are never painted.

 

[Mbrooke]

@NolaScience: Thank You for the information. I was not aware that Michoud was decommissioned.

GSU means generator step up transformer. So if there is 300MVA GSU, there is typically a 240kW generator behind it.

 

[Eeyore11]

I think you mean Power Blvd, but ok.

Powerline Dr

https://maps.app.goo.gl/KQCqTLq36CqzMm757

I am not local, but the street sign seems to match. Stay safe down there!

 

[FacEngrPE]

Power line drive at the river showing the tower,

https://www.google.com/maps/@29.936...4!1shBrI0dD2BYYiYSK61-p17g!2e0!7i16384!8i8192

Turn the view around, and see the this anchor structure

https://www.google.com/maps/@29.937...!1s8cjkYIu93x1GhYTo11-OrQ!2e0!7i16384!8i8192.

It looks like a two circuit crossing, but it really is only one.

Plan view

https://www.google.com/maps/@29.9361587,-90.1891818,324m/data=!3m1!1e3

Tower on the other side of the river

https://www.google.com/maps/@29.9280091,-90.1793542,324m/data=!3m1!1e3

This is an impressive river crossing.

 

[NOLAscience]

That is an obscure little street. Idk why I didn't find it when I searched for it on Google Maps.

 

[3DDave]

There was a report the system had gotten a good going over 3 years or so ago - but that one tower looks like the improvement was to only the upper portion as if they kept the old base and just did the insulators and support structure.

 

[mc5w]

dlc: New York City has quite a bit of 345 KV underground cables and they are very reliable. One of the NYC power outages was that lightning stuck a double circuit overhead tower north of the city where the 6 circuit 345 KV main line ran over a solid rock hilltop. The lightning caused those 2 circuits to flash over causing the load to shift to the other 4 circuits in turn causing those to sag all the way into the ground. They ( Consolidated Edison ) should have had a now defunct company named Grounding Perfection sink ground rods about 90-100 feet deep into the solid rock. Patent 8,439,125 details how to achieve deep earth grounding in solid rock as well as ordinary soil.

There are 3 other problems with underground wiring besides the expense of installing it. One of them is reactive power control which is that there have to be periodic shunt inductances to tune out the no load charging current of the insulation. These need to be adjustable so that some of the inductance can be removed during peak periods. The next is that the propagation velocity of alternating current in a shielded cable can be a lot lower than in an overhead line. According to one of the 8 volumes of A History of Engineering and Science in the Bell System the propagation velocity of a power or telephone transmission line that has a lot of reactive compensation the propagation velocity can be as low as 10,000 miles per second. This poses grid stability problems because when a power plant is 1/8th or greater wavelength from the load the plant has problems with sensing what the load is doing and at 1/4 wavelength the plant cannot sense the load at all without active feedback from a sensor close to the load via radio link or fiber optic cable.

Another problem with underground wiring is that when it breaks it is a major Pain In The Arse to repair or replace. I have replaced enough 200-amp underground electrical services (1) to know this. I had to put in a 200-amp temporary service next to the padmount transformer because the new service had to go right where the old service was. I also had to run an overhead rather hefty feeder line to supply the house and had to run it over the neighbor's property. I got the old electrical service wrapped around the digging bar TWICE. One thing that did go right was that Summit County, Ohio outlawed direct burial electrical services partly because of failures due to the Tree Root Circuit Breaker Method. Sure, National Electrical Code allows direct burial services but using schedule 80 PVC pipe saved the backbreaking work of removing rocks from backfill, removing rocks from the bottom of the trench, etc.

I later found out that Summit County has had problems with marijuana growers going through a basement wall and hot tapping underground services ahead of the meter. This is so that the power company would not notice that a well insulated house was using say 14,400 kilowatthours per month. Ilsco nakes a device for hot tapping insulated wires without using insulated hot line gloves which makes power theft very easy.

Actually, it looks like what caused the Protective Earth Neutral conductor of this service to go open circuit right during the 2002 Super Bowl was the Trre Root Circuit Breaker method. The homeowner or his predecessor had planted evergreen trees right smack dab on top of the old service. In this version a root had penetrated the PEN causing the aluminum to undergo electrolytic corrosion. Also, if tree roots are wrapped around underground facilities wind blowing over the tree tends to rip up what is down there.

I have also read about instances of where a neighborhood was converted from underground distribution to overhead distribution because too many 2-legged or 4-legged gophers and mice had broken the wires. Mice like to chew on the wires and it only takes 1 dingbat who thinks that he is a member of the Trick and Precision Digging Team to break underground wiring.

On the other hand, an American Electric Power 7,620Y13,200-volt line along Mount Calvary Avenue here in Columbus is a good candidate for underground wiring because the poles are leaning over due to soft soil. This past November 15, 2020 wind blew one of the phase conductors into the metal cap at the top of the wall on the west side of our building. The 7,620 volts then went around the corner and made the south and west sides of our apartment building fry like bacon. I posted pictures of the damage on my Facebook pages titled Human Voltmeter Method.

 

[mc5w]

Also, Cleveland Electric Illuminating Company has lattice work steel towers that are this high where their 4 circuit 138 KV backbone goes over Interstate 480 and the southern sewage plant just west of I-77. I am glad that I do not live in New Orleans and instead in Columbus, Ohio.

 

[FacEngrPE]

https://charts.noaa.gov/PDFs/11370.pdf

149 ft clear below power cables. Two circles with center dot marked tower, one is near the Avondale Shipyard.

 

[NOLAscience]

Protective Earth Neutral conductor of this service to go open circuit right during the 2002 Super Bowl was the Trre Root Circuit Breaker method

Are you sure it was the 2002 Super Bowl? There was an outage at the then Mercedes-Benz Superdome during the 2013 Super Bowl in New Orleans. I remember that it was reported at that time that there had been an outage at a previous Super Bowl, but I can't find anything to confirm that right now, nor to tell me which one had the outage.

And which homeowner's tree caused the problem? Was it near the stadium?

 

[NOLAscience]

As a Civil/Structural, I just have to say that the underdesign (by any rational engineering method) of power poles has been discussed amoungst my colleagues several times over the years. The electrical and facilities engineers at our company used to say, "Don't let the structurals get involved with any power line supports. You will end up with a huge foundation and massive poles."

Each power pole could have a foundation that would be able to resist the wind load on the pole and wires (tree loads, not so much), but (1) design cost would be prohibitive -- soil tests, how often??; and (2) construction cost would go up exponentially. It is definitely cheaper for the power companies to install poles that are 'ok' up to about 35 mph and to replace the ones that are blown down in hurricanes and other strong storms. Now, if you added the cost of every "whole house" generator and even portable generators owned and maintained by the millions who live in the path of hurricanes, they might see things differently. But they can just charge us a "Hurricane Ida Restoration Fee" and get all of this rebuilding cost back, so why bother?

 

[FacEngrPE]

NOAA Geodetic Survey Post Ida storm photography is now posted at

https://storms.ngs.noaa.gov/storms/ida/index.html#9/29.9049/-89.8448

The photography is very high quality, but only incidentally covers power infrastructure. The river crossing at Waterford (Little Gypsy Power Plant) can be found - this one is undamaged. The OP subject fiver crossing is not in frame.

https://oceanservice.noaa.gov/news/aug21/ngs-storm-imagery-ida.html[/URL]][ul]
[li]August 30: One flight covering the coast of Louisiana from South of Lake Charles to Atchafalaya Bay; State Route (SR) 56 to Houma and SR 24 to SR 1 South to just short of Grand Isle; some of SR 90 into New Orleans and a small portion of SR 23.[/li]
[li]August 31: One flight covering SR 90 from Gibson to Raceland; then South to Houma and SR 97, returning through Houma on PR 111/SR 315; from Houma, proceeded East to SR 3235 and LA 1 South to Port Fourchon and Grand Isle; then flew from Grand Isle East to the mouth of the Mississippi River North to Woodlawn. At the end of the mission, the aircraft traveled to Mobile, Alabama, collecting images of the Chandeleur Islands and most of the Mississippi coast prior to landing.[/li]
[li]September 1: One flight in and around Lake Pontchartrain, the Gulf Intracoastal Waterway, and West of Fourchon; weather conditions limited flight.[/li]
[li]September 2: One flight that covered various locations in Louisiana and Mississippi, completing all FEMA and U.S. Coast Guard imagery requirements.[/li]
[/ul]

 

[bacon4life]

NOLA- Are you talk about A) engineers not designing to code or B) The NESC being inadequate?

Power poles over 60 ft need to be designed for 85 to 150 mph per the NESC/AASHTO wind map below. If engineers are not meeting code, they should be reported to the state board.

Many folks think the NESC is inadequate for short structures along the Atlantic coast. In my region, the 60ft exemption has little practical impact on reliability because the pole strength requirements here tend to be driven by combined wind/ice loading. Hopefully one of the change proposes for the 2023 NESC will find a way to make the Atlantic coast wind requirements more reasonable without requiring everyone in my region to do additional, irrelevant, analysis on every distribution pole.

 

[NOLAscience]

NOLA- Are you talk about A) engineers not designing to code or B) The NESC being inadequate?

The power companies certainly don't do soil tests to determine how deep to embed the timber power poles that are placed every 100' on thousands of miles of roadways in Louisiana. They place their standard pole at a standard depth. [CLECO replaced a power pole in our back yard after Katrina, and I must say, they used good soil for the backfill.]

Entergy alone has 5400 miles of transmission lines. I'm sure they assume the worst possible soil conditions and design from there, but in the 1970s, power companies were allowed to design for only 95 mph.

Transmission towers are designed for higher wind loads, and they would have geotechnical reports for each tower project.

The current NESC wind loads appear to be quite adequate, although I've not used the NESC in many years.

Here's some good information on the issues:

https://www.reuters.com/business/en...a-crippled-new-orleans-power-grid-2021-09-04/