On Feb. 2nd 2011 :
A trio of events - loss of supply, higher demand and maintenance outages - led to Wednesday's emergency rolling blackouts across Texas and spiking power prices as the grid operator for most of the state struggled to accommodate a brutal winter storm.
Here is my collection of events from various links...
In 2008, Texas has been on the edge of a rolling blackout.
"On February 26, 2008, the Electric Reliability Council of Texas (ERCOT) called for an Emergency Electric Curtailment Plan (EECP) at 18:41 due to a worsening imbalance between generation and load which led to a decline in system frequency"
Read here (http://www1.eere.energy.gov/windandhydro/pdfs/43373.pdf)

In 2011, (Feb 2 & Feb 3) Texas has suffered from blackouts. The Oil Drum has a nice summary of the events : ( http://www.theoildrum.com/node/7449 )
A summary of events is available from this site : (http://www.oncor.com/news/newsrel/detail.aspx?prid=1297)
"Wednesday’s peak demand is currently projected to be more than 54,000 MW between 8-9 p.m. , and more than 58,000 – which would be a new winter record – between 7-8 a.m. on Thursday. The current winter peak demand record is 56,334 MW which occurred Feb. 2, between 7 and 8 p.m.
The grid continues to have about 2,700 MW of generation capacity unavailable because of unplanned or forced outages."

These 2700 MW of generating capacity are probably these two plants:

Texas Lt. Gov. David Dewhurst said the Luminant-owned 1,640 MW Oak Grove plant east of Temple and the 1,137 MW Sandow plant near Rockdale were among the plants knocked offline by the storm. Oak Grove suffered a broken pipe and Sandow was hampered by a frozen pipe. Allan Koenig, communications director for Luminant, said its Oak Grove and Sandow power plants "accounted for just a small percentage of the 50 units and 7,000 megawatts."

So it was cold weather, pipes and low pressure on natural gas lines:

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.
I am not quite sure about this:
But, Fraser said, some power cuts affected some stations for compressing natural gas — so without power they couldn't pump gas, causing some gas power plants to go offline
The complaints followed :
"The blackouts left many people angry and frustrated. Cuellar said Oncor’s call center has been overwhelmed with about 60,000 calls an hour."
Also a family blamed these outages for causing their son's death

So the market worked and prices soared to 3000$/ MWh

As a result of the outages and demand, real-time power prices peaked around $3,000/MWh during some intervals Wednesday afternoon.

Average prices at this time of year normally would be less than $100/MWh, Doggett said.
Emergency measures started:

In addition to the default Energy Emergency Alert 0, or normal operations, there are four EEA levels: EEA Level 1, EEA Level 2A, EEA Level 2B and EEA Level 3, which is the most extreme.

ERCOT first contacted market participants at 4:45 am CST on Wednesday to warn the companies of inclement weather. ERCOT declared EEA Level 2A at 5:17 am

Less than a half-hour later, ERCOT declared EEA Level 3 at 5:43 am, at which point the grid operator asked distributors to shed firm load of 1,000 MW, said ERCOT spokeswoman Dottie Roark.
A timeline and detailed discussion is available from here:

More information about Texas home heating is available here

As a final reading, I offer "Normal Accident Theory" from NASA:

Failure in one part (material, human, or organization) may
coincide with the failure of an entirely different part. This
unforeseeable combination can cause cascading failures of
other parts.
In complex systems these possible combinations are practically

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