Identify Plant or Unit
Operating Environment
Critical
Equipment
List
Compile Data
Determine Analysis Strategy
Assess Risk Tolerance
Introduction
Identify the Specific Plant or Unit
This initial step is all about the prioritization of time and resources needed to confidently determine minimum plant temperatures. Criteria for prioritization include focusing on large capacity generators that contribute significantly to grid stability and how individual units performed during cold conditions in the past. Another factor to consider in determining where to focus resources is whether a thermal plant is slated to cease operations soon.
Identify the Operating Environment
Plant operators can also take steps to assess and prepare for extreme weather conditions under the NERC EOP-012-1 standard. The standard prioritizes pinpointing the lowest temperature plants have reliably operated in historically and determining if there is a gap between that performance and required minimum temperatures. Methods to identify any gaps include evaluating the possibility equipment will freeze, whether fuel supplies are reliable, and how wind, snow, and ice impact critical systems.
Utilize a Plant's Critical Equipment List
Certain equipment at a plant is essential for a unit to startup or to operate reliably. Identifying and documenting which equipment is critical should be followed by an assessment of its vulnerability to extreme cold. Equipment that can often be deemed critical includes transmitters, instrument air systems, and water pipes with fire suppression systems.
Assess Risk Tolerance
Determining a plant's minimum startup or operating temperature means being clear-eyed about the data and analysis used to do it. For example, if critical components fail and risk plant outages or reduced capacity, lower analysis confidence could encourage the use of conservative safety margins. Startup temperatures that require interventions are riskier than those that don't. Ultimately, plants that have low-risk tolerance should implement multiple protective measures.
After identifying critical equipment, the next step is to gather as much information as possible about what makes it vulnerable to low temperatures. This can include collecting specified temperature limits for outdoor equipment and evaluating ancillary equipment like heat lamps and temporary enclosures that can be used to maintain minimum operating temperatures.
Compile Data for Critical Equipment at Greatest Risk
Choosing the best analysis strategy depends on the available data, which can range from manufacturer specifications to operating histories or engineering analyses based on design sensitivity to cold. The strategy must adapt to the data quality and include caveats like startup time, safe human intervention, and material supply reliability. Operating history can be helpful, but it must account for variables like weather. When equipment has limited data or history, confidence in the analysis inevitably decreases.
Determine the Best Analysis Strategy
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Framework Basics
Clearly, every operator must determine the most accurate way to calculate the minimum operating temperature at a thermal plant.
EPRI's report outlines several steps plant operators can follow to establish minimum operating temperatures.
Introduction