Appendix H - Operations During Cold Weather Conditions

There are three distinct levels of weather situations that may precede ISO New England calling a Cold Weather Event:

  • Cold Weather Conditions means any calendar day when that day's Effective Temperatures are forecast to be equal to or less than zero degrees Fahrenheit for any single on-peak hour and that day's total Effective Heating Degree Days are forecast to be greater than or equal to 65.
  • Cold Weather Watch means Days when Cold Weather Conditions are forecast to exist and the 7-Day Capacity Margin Forecast indicates a capacity margin greater than or equal to 1,000 MW.
  • Cold Weather Warning means Days when Cold Weather Conditions are forecast to exist and the 7-Day Capacity Margin Forecast indicates a capacity margin less than 1,000 MW.  In addition, a Cold Weather Warning will be used for all future days within the 7-Day Capacity Margin Forecast when a capacity margin of less than or equal to 0 MW exists for days not yet declared as a Cold Weather Event.
  • Cold Weather Event means Days when Cold Weather Conditions are forecast to exist and the 7-Day Capacity Margin Forecast indicates a capacity margin less than or equal to 0 MW for an Operating Day.  Cold Weather Events are declared by 1100 hrs two days prior to the Operating Day. A Cold Weather Warning will be used for all future days within the 7-Day Capacity Margin Forecast when a capacity margin of less than or equal to 0 MW exists, until such time that the ISO declares a Cold Weather Event.
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