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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. The "polar vortex" that enveloped much of the Eastern U.S.  in January 2014 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. 

Generator Winterization Survey

The Generator Winterization Survey for 2018-2019 is now open.

NERC Findings and Recommendations

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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