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Weatherizing Generating Units

MISO urges asset owners to weatherize generating units per the recommendations of the North American Electric Reliability Corporation (NERC).

Severe winter weather can cause icing and other mechanical problems for electricity generating units. For example, in February 2011, 225 units in the Southwestern U.S. were tripped, de-rated or failed to start entirely due to frigid temperatures and high winds. Both the “polar vortex” that enveloped much of the Eastern U.S. in January 2014 as well as the February 2021 cold weather event caused similar problems. MISO urges asset owners to ensure that generating units are adequately weatherized. This will help fend off forced generation outages that can jeopardize grid reliability. 

FERC/NERC Final Report - February 2021 Cold Weather Event

Nine months after extreme cold weather gripped Texas and the South Central U.S., FERC, the North American Electric Reliability Corporation (NERC) and NERC’s regional entities issued a final report examining the impact the February 2021 freeze had on the bulk electric system. The report found a combination of freezing issues (44.2 percent) and fuel issues (31.4 percent) caused 75.6 percent of the unplanned generating unit outages, derates and failures to start. 

Key Takeaways from MISO’s February 2021 Arctic Event Report are consistent with the findings from the FERC / NERC report, including:

-        The need for increased generator winterization requirements,

-        The need for gas industry winterization and the importance of coordination across the electric and gas industries,

-        The need for good situational awareness leading up to and during events (including enhanced weather, load, and outage forecasting,

-        More flexibility and coordination of load shed protocols during winter events, given the recognition that extreme weather events are becoming more frequent and have the potential to take a major toll on public safety.

The FERC / NERC report lists 28 specific recommendations including enhanced winterization standards for generator operators. 

NERC Findings and Recommendations - 2011 Cold Weather Event

NERC, the reliability authority for the bulk power system, found that many of the forced outages associated with the February 2011 severe weather event occurred because generators failed to adequately prepare for frigid temperatures and high winds. NERC said all types of generation except nuclear exhibited weatherization-related shortcomings, including:

  • Failed or insufficient heat-tracing equipment 
  • Missing or inadequate wind breaks around key components
  • Removed, damaged or inadequate insulation
  • Failed or inadequate heating elements instrument cabinets
  • Freeze-protection equipment not on hand

NERC issues 13 "lessons learned" in the wake of that event that it urged generators and other entities to implement to reduce weather-related forced outages. NERC's findings, which MISO supports, recommend that generators consider taking a number of action as part of their winter operation plans, including:

  • Erect permanent wind-break structures
  • Install temperature gauges in transmitter boxes and monitor them regularly
  • Ensure that heat-trace systems and insulation are properly applied on critical components
  • Have sufficient staff onsite during sever weather events 
  • Install covers on valve actuators to prevent ice from accumulating
  • Install monitors and alarms to give advance warning of freeze-related problems in critical areas

Additional Information

NERC's other weatherization-related recommendations address subjects such as maintenance and inspection practices; fuel-switching procedures; and winter operations training for unit operators, among other things. NERC's 13 recommendations that grew out of the 2011 severe weather event can be found on NERC's website

NERC's report on the 2014 polar vortex also addresses weatherization-related issues and can be found on NERC's website

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