Final Report Released on February Electric Grid Outages

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Final Report Released on February Electric Grid Outages

November 29, 2021

The Federal Energy Regulatory Commission (FERC), North American Electric Reliability Corporation (NERC) and various regional entity staff Nov. 16 released their final report and recommendations on the February 2021 Cold Weather Outages in Texas and the south-central United States.

The recommendations contain serious implications for Minnesota utilities, energy system planners and policymakers.

The event was the fourth cold-weather-related event in the last 10 years to jeopardize bulk electric system reliability. It was the largest series of rolling blackouts in U.S. history and reached into western Minnesota. More than 4.5 million people in Texas lost power during the event, with some exposed to below-freezing temperatures for over six days. At least 210 people died of causes tied to the power outages.

The report noted the 2021 event was part of a recurring pattern for the last 10 years. First, generating units failed in large numbers. In the wake of massive natural gas production declines, the natural gas fuel supply struggled to meet demand, worsened by the increasing reliance on natural gas-fired electric generating units.

The event began with extreme cold temperatures and freezing precipitation. Natural gas generating units common throughout Texas and the south-central U.S. and natural gas production infrastructure are vulnerable to freezing and wind turbines are vulnerable to blade icing.

During the week of Feb. 7, the Electric Reliability Council of Texas (ERCOT) and Southwest Power Pool (SPP) experienced rising electric demand and generating unit outages, primarily caused by wind turbine blade freezing and natural gas fuel supply issues.

Far colder weather came the week of Feb. 14. With freezing precipitation and severe cold invading the region, increasing generating unit outages and record electricity demands, ERCOT, SPP and Midwest Independent System Operator (MISO) operators were faced with “the perfect storm.”

ERCOT ordered rotating blackouts the early morning hours of Feb. 15, ultimately shedding 20,000 megawatts (MW) of firm load at the height of the event. SPP and MISO also shed load Feb. 15-16, with the SPP outages reaching into western Minnesota.

ERCOT did not anticipate that rolling blackouts would contribute to power outages of natural gas production and processing facilities. During the Feb. 15-16 time frame, power outages were caused by both weather and firm load shed. According to the report, the extent of power outages that can be attributed to critical natural gas infrastructure limitations and subsequent load shed is unknown because many critical natural gas infrastructure loads had not been identified.


The FERC-NERC staff report on the February outages contains 28 recommendations. Some may be of particular interest to MMUA members.

Key Recommendation No. 7 addresses fuel availability and highlights the value of dual-fuel capable electric generators. These units are common in municipal electric generating plants.

Units capable of fuel switching have both economic and reliability benefits, notes the report. Benefits include allowing operators to purchase the cheaper of two fuels and have an alternate source of fuel if one source is interrupted or curtailed. In ERCOT, 41 of 392 generating units are capable of fuel switching, yet only roughly a third attempted to switch from their primary fuel to their secondary fuel during the Event.

Approximately 86 percent (12 out of 14) generation units that attempted to switch fuel types in ERCOT failed or reduced generation. The majority of units that attempted switching were gas generators switching to distillate oil or oil.  Failures in fuel switching were due to problems including the blade path temperature spread from uneven burning of oil, fuel oil pump fouling, fuel oil system trip, fire in turbine enclosure due to fuel oil leak, valve failure, never operated on alternate fuel, inability to synchronize on alternate fuel source due to loss of flame issues during startup, and inability to synchronize on alternate fuel source due to failure to accelerate fault during startup.

In MISO South, four entities reported owning a total of nine dual-fuel units, and one unit was asked to operate on fuel oil due to natural gas fuel restrictions. The unit used a propane system for starting and contributed up to 120 MW of generation from Feb. 15-17. Generating units in SPP that switched fuels contributed an average of 1,300 MW of generation during the height of the Event from Feb. 15-18.

The fuel-switching recommendation was first made in NERC Reliability Guidelines issued after a 2011 cold-weather event.

The very first Key Recommendation issued in November addressed Electric Generation Cold Weather Reliability and urged revision to the NERC reliability standards to require generator owners, including wind generators, to understand the effect of precipitation wind chill on equipment.

The recommendation urged that Generator Owners who are retrofitting existing generating units or building new ones be required to design the units to perform at the lowest ambient temperature for the nearest city for which historical weather data is available, factoring in accelerated heat loss due to wind speed. This recommendation has serious implications for Minnesota, with ambient temperatures often colder than wind turbine cold-weather shutoff limits.

Generator Owners, recommends the report, should be compensated for cold-weather upgrades necessary for any new units they may build and should have the opportunity to be compensated for the costs of retrofitting existing units to operate to a specified ambient temperature and weather conditions.

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