Texas Rolling Brownouts 4

[electricpete]

What's the scoop with the rolling brownouts statewide on 2/2/11?

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[electricpete]

It took awhile to find anything in google. Here are a few tiny details:

http://www.wtaw.com/2011/02/02/rolling-outages-suspended-were-started-after-2-plants-shut-down/

Burst water pipes at two coal-fired power plants forced them to shut down, triggering rolling power cuts across the state, the lieutenant governor said Wednesday. Lt. Gov. David Dewhurst said this is something that “should not happen.” Dewhurst said he was told that water pipes at two plants, Oak Grove and Sand Hill, forced them to cut electricity production. Natural gas power plants that should have provided back up had difficulty starting due to low pressure in the supply lines, also caused by the cold weather. The lieutenant governor said the demand placed on the Texas grid was nowhere near peak capacity. He said he was frustrated by the situation. The statewide electricity authority ordered cities across the state to start rolling power outages to cope with the crisis.

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[rmw]

We lost power 4 times throughout the day at work today in the Galleria area of West Houston. First outage was right after 7:00 AM. It was a fruitless day. It typically took the network about 45 minutes to catch up once the power came back on. And about that time another black out would occur.

I was sweating bullets when I got on the elevator to go to the parking garage at the end of my shift today. I could just see being stuck on the elevator on the way out of the building.

There is a certain irony to my company being without power, but I can't be specific.

rmw

 

[rmw]

Oh, and by the way, ours wasn't a brownout, it was a pure and unadulterated BLACK out.

rmw

 

[electricpete]

West of Houston... plenty of power traders around there.

http://www.dallasnews.com/news/comm...lackouts-wednesday-night-thursday-morning.ece

The planned outages, which lasted up to 45 minutes, were triggered when more than 50 power plants, including a few owned by Dallas-based Energy Future Holdings, stopped working Tuesday night because of the cold weather.

The Electric Reliability Council of Texas said 7,000 megawatts of generating capacity tripped Tuesday night, leaving the state without enough juice.

I have a suspicion there is a little more to the story than just a bunch of different power plants (50?) all had problems from the cold weather.

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[electricpete]

Underfrequency protection of generators is an interesting proposition where the goals of generator protection and system stability conflict. I wonder if that played any role in this event.

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[rmw]

I wonder if we (the public) will ever know.

I wonder if we (those inside the industry) will ever know.

rmw

 

[ScottyUK]

ePete,

Gas turbine prime movers usually have a very steep output roll-off as frequency drops because the compressor quickly loses its ability to deliver enough combustion air into the power turbine. They are far from an ideal machine to help the system ride through a major system disturbance. Any idea what the mix of generation is in that area - I suspect there is probably a lot of gas-fired plant.


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If we learn from our mistakes I'm getting a great education!

 

[electricpete]

Texas power as many know is separate from the rest of the US (except for small dc tie lines).

I know we have the typical sources: gas, oil, nuke wind. Maybe someone knows a link with a summary of power types.

I remember hearing we have the most wind of any state. Wind I imagine is susceptible to being affected by weather, but I have no info to suggest that was the case.

I can see gas turbines are relatively susceptible to fluctuations in gas supply. I know a lot of small gas turbines have gone in over the past years. The older bigger gas plants used gas to fire boilers for steam turbines… all of those have the capability to switch between gas and alternate fuel and I’d think they would switch before a severe weather event that everyone knew was coming for days.

I did read on-line somewhere that in addition to the 7,000MW lost, there was already 12,000MW out for maintenance when things began.

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[rcw retired EE]

My bet is that most of the combined-cycle gas turbine plants in Texas are not equipped for cold weather with adequate heat tracing to keep critical lines and drains from freezing. In the design stage, the design ambient temperature was probably 2C or just above freezing. The plant owner's saved $1.5M-$2M on heat tracing that is not needed if it never gets cold.

Many of the combined cycle plants do not have bypass stacks on the gas turbines, another feature not considered necessary in the North American market. That means if the gas turbine is going to run, the Heat Recovery Steam Generator (HRSG) connected to it has to be able to take the exhaust heat. But the HRSG can't do that if its condensate lines and steam drains are frozen or already split open by the freeze. Or maybe the cooling tower froze up or the lube oil and generator cooler lines froze.

Another factor is the pipeline gas pressure is probably way down. All houses and business's are using a lot of gas to keep warm. The pressure may be below the minimum operating pressure at the plant. Or maybe the gas compressors' cooling water lines froze. Backup fuel oil systems need auxiliary heaters to get the fuel to operating temperature. Maybe the heaters are undersized for the actual ambient temperature.

When Mother Nature doesn't obey the Design Criteria, stuff happens.

 

[rmw]

What RCWilson is mostly true, but I heard a report yesterday that it was a couple of coal plants (might have been lignite) in central Texas that precipitated the crisis. I can't recall their names now, but I did recognize them at the time.

What most plants in the coastal regions are not ready for is temperatues in the low '20's (F). As RCW has pointed out, not a lot of stuff is heat traced because it is just not normally needed.

While the reports said burst water pipes, I suspect frozen instrument air lines. It is not necessary either to have instrument air dryers that go much below 32F in this part of the world, so temps in the '20's will get the moisture in them every time. But that is not so much based on reports as my own personal expernience in many of the typical power plant in the region, gas, coal or nuclear.

Plus the fact that other than one short cold snap last year, for the last several years, global warming has been so bad that it didn't even get cold enough to kill the mosquitos in the region, much less freeze a pipe or air line.

Add to that some of the ice load in the transmission lines in the northern portions of the ERCOT island, and the plants up there that are weatherized are not much help.

Add to that that at least two of the small DC ties outside the 'island' that EP mentions are into regions that have their own share of winter issues, there isn't much relief there either.

All of it adds up to a nasty surprise yesterday morning. I don't think the emergency generator for our building was ready either. I sat in the total dark (I was at my desk) for several minutes before the emergency lights kicked in. I had not docked my laptop yet as I was waiting till the battery depleted completely so the screen was all the light I had.

rmw

 

[byrdj]

I checked the nrc.org and i didn't see the loss of a nukie this am, but I did find this interesting article

http://www.reuters.com/article/2008/02/28/us-utilities-ercot-wind-idUSN2749522920080228

the jest is a sudden loss of winds (with out spinning reserve) was the initation

 

[dpc]

Wind failure - I love it. They just need to get the Texas Legislature out to a wind farm.

David Castor

http://www.cvoes.com

 

[racobb]

Please say it ain't so! You mean that the wind isn't always at its max during peak demand periods?

Alan

 

[byrdj]

Found several news article now where they named names

http://www.pennenergy.com/index/pow...nd-d-infrastructure/2011/02/ERCOT-outage.html

one of the stations blamed only went commercial in the last few months (1.6GW)

 

[electricpete]

Interesting links.

The reuters article points a finger at wind. I was wondering how 50 plants could have gone down... now it makes more sense if it was a lot of small wind plants forced off by a common factor (ferocious winds) more ubiquitous than inadequate heat tracing.

The Pennenergy articles mentions no fault for wind but instead quotes a wind energy spokesman on how much wind was on-line helping in the time of need.

Which is closer to the truth I think will become clearer over time.

The Pennenergy article mentions someting about 15% of 7000MW out for maintenance initially... that might be in the neighborhood of almost 1200MW. In contrast a Forbes columnist mentions 12,000MW out for maintenance initially:

http://blogs.forbes.com/christopher...outs-force-texas-to-import-power-from-mexico/

What's a factor of 10 among friends?

This was a pretty severe event both in terms of actual impact (statewide outages when people needed heat on the coldest day of the year) and potential impact (how close were we to losing a whole bunch of generators on underfrequency... we got to stage 3 which is last resort stage to prevent total system failue).

Given the severity, I was frankly amazed how difficult it was to find basic info about this event, but now I guess it is part of the deregulated competitive environment. If info was released that allowed people to judge the near-term prospects for generation, it is insider information that gives some a competitive advantage/disadvantage in the electricity market.


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[racobb]

Thanks byrdj!

Alan

 

[electricpete]

"now it makes more sense if it was a lot of small wind plants"
should have been
"now it makes more sense if it included a lot of small wind plants"
i.e. the large number 50 is more easily understood when we consider it includes a lot of small plants. The wind plants explain the large number but not the total losss... wind loss reported as only 1700MW out of 7000 total according to Reuters. Again I think it will become clearer over time ...I'm trying not to jump to conclusions yet.


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[electricpete]

Google led me to this one which takes the cake for funniest article by someone who isn't trying to be funny:

http://www.infowars.com/rolling-bla...ty/?utm_source=twitterfeed&utm_medium=twitter

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[wayne440]

The article above makes a good argument for requiring an IQ test before one is allowed to publish.