By John Kemp
LONDON (Reuters) - Following last week’s widespread power failures, Texas policymakers and the state electricity industry must decide whether the blackout was caused by genuinely unforeseeable weather conditions or a failure to plan properly.
For 10 days, Texas was hit by an unusually prolonged period of very low temperatures, with the most intense cold occurring between Feb. 14 and Feb. 17.
Electricity consumption surged across the state while many generating units failed to start up owing to frozen instrumentation, iced turbine blades and insufficient fuel supplies.
The result was widespread blackouts, in some cases lasting for more than 24 or 48 hours, as grid controllers tried to protect at least some parts of the grid from collapse.
Failure to winterise generating units to ensure they would operate during extreme low temperatures has already been identified as one of the leading sources of the power failure.
The question remains whether grid operators and generators could have reasonably foreseen the low temperatures and should have taken steps to prepare for them.
The answer is "Yes".
FORESEEABLE RISKS
Local temperature records from multiple locations across the state strongly suggest the extreme heating loads and widespread generation failures experienced last week should have been reasonably foreseeable.
Temperatures had been almost this low at least once a year on average for the last century, so a temperature slightly lower still was foreseeable and should have formed part of grid planning.
Managing low-probability, high-consequence “tail risks” is central to reliability and resilience planning in the electricity industry (as well as in banking and safety-focused industries such as aviation).
The Texas grid should have had an operational plan to remain reliable with the low temperatures recorded last week.
Even if the operating plan could not ensure that load was fully served, it should have had a contingency plan to ensure stability while minimising the loss of load.
Instead, the grid blew rapidly through multiple layers of protection, forcing the control room to take emergency action to avert a complete collapse.
If the grid had been prudently planned and operated, it should never have come so close to complete failure.
ENSURING RELIABILITY
Like the soundness of a bank, the electric grid’s reliability is only revealed under extreme stress; but when the Texas power network was stress-tested last week, it failed.
In normal conditions running a bank, taking deposits and making loans, is straightforward and highly profitable, requiring only a moderate level of professional skill.
In a business-cycle downturn, however, loan losses can increase quickly, while depositors may demand their money back if they fear for the bank’s soundness.
Banks suddenly face pressure on all aspects of their business simultaneously, and the stress on their financial condition rises exponentially.
The test of resiliency and soundness, as well as the quality of a bank’s management and risk-control systems, is how it performs during a downturn rather than in more favourable conditions.
Prudently managed banks are those that survive through multiple downturns without failing or requiring a taxpayer bailout.
In the same way, running an electric grid, scheduling generation and supplying load, is fairly straightforward and profitable under normal operating conditions.
The grid’s resilience and the quality of its management and systems are only revealed when it is put under stress, usually by a heatwave or cold weather.
Under these conditions, electricity consumption increases to many times the average level, while generation may become unavailable because units overheat or will not start owing to the cold.
Transmission lines become overloaded, instruments fail, cooling water systems are unable to operate effectively, and fuel supplies prove inadequate.
Power quality and frequency control degrade, situational awareness in the control room deteriorates, and the probability of power failures rises exponentially.
The test of a well-run grid is how well it copes with the pressure under relatively extreme circumstances without widespread failure.
DAILY MINIMUMS
Boerne, Kendall County, is a small town in the Texas Hill Country, but it has an unusually long and complete series of daily temperature observations stretching back for more than a century.
On both Feb. 15 and Feb. 16, the daily minimum temperature in Boerne fell to a low of -14 degrees Celsius, according to daily records compiled by the U.S. National Oceanic and Atmospheric Administration.
Temperatures have only fallen this low at Boerne on 12 occasions since 1904, a frequency of roughly once every 10 years; the last times temperatures were this low were in December 1989, March 1988 and February 1985.
But while the extreme lows experienced last week were unusual, it is not uncommon for the temperatures to fall almost as far (https://tmsnrt.rs/2ZOc0Ku).
Temperatures at Boerne have fallen to -10 degrees Celsius or below on 115 days since 1904, an average of about once per year.
And temperatures have fallen to -5 degrees Celsius or below on more than 900 days since 1904, an average of eight times per year.
Extremely cold weather is not uncommon in central Texas – even if it rarely becomes quite as cold as it did last week.
Daily minimums at Boerne have been highly variable, ranging from a high of almost +29 degrees in July 1987 to a low of -20 degrees in December 1949, with a mean of +12 degrees.
Minimum temperatures recorded last week were just over 3 standard deviations away from the mean, so they were rare, but not unforeseeable.
The distribution of daily temperatures and last week’s position in it were similar at other weather stations in the state that have similarly long records, including those at Albany, Sulphur Springs and Corsicana.
At other locations, minimum temperatures last week were also just over three standard deviations away from the mean, so they were rare, but not incomprehensible.
The Texas grid should have been prepared for the cold weather that hit the state and should have been able to maintain near-normal operations.
The fact that it could not cope, plunging millions of customers into darkness without heat for hours or days at a time, indicates a serious planning failure.