A Minimum Generation Emergency is a type of abnormal system condition the ISO declares when it anticipates that generation and external transactions will exceed system demand, which could result in excessively high system frequencies and unscheduled flows of power into neighboring regions. For example, if a widespread power outage occurs that greatly reduces the region’s demand for electricity compared with the forecasted demand, the ISO may declare a MinGen Emergency to reduce the excess amount of electric power available.
During a Minimum Generation Emergency, the ISO anticipates requesting at least one generator asset to operate at or below its economic minimum limit to manage, alleviate, or end the emergency. The ISO will issue a Minimum Generation Warning when an assessment indicates that generation could exceed the region’s demand for electricity. The warning lets generators and neighboring regions know that the ISO is seeking voluntary reductions in generation and external transaction imports. Ideally, a Min Gen Warning would be declared before a Min Gen Emergency, but an emergency can be declared without declaring a warning.
Reference: Minimum Generation, Procedure CROP.25005
The ISO may declare a Minimum Generation Warning when the sum of external transactions, all on-line generating units at the economic minimum (ecomin) limits, and demand-response resource (DRR) minimum-reduction megawatts (MW) minus the projected system demand for all of New England is less than 300 MW.
The ISO declares a Minimum Generation Emergency when the sum of fixed external transactions on the noncoordinated-transaction-scheduling (CTS) interfaces that cleared the Day-Ahead Energy Market and the ecomin limits of all on-line generators is within 100 MW of the projected demand or greater than the projected demand.
As an example, starting with regional system demand at 10,000 MW and with 9,900 MW of fixed external transactions plus generation at ecomin (supply), a Min Gen Emergency would be declared if the demand decreased or the supply increased to a point where the difference between the demand and supply were less than 100 MW, which could lead to the supply exceeding the demand.
The ISO performs the Reserve Adequacy Assessment (RAA) to ensure the proper amount of resources are scheduled in advance to meet the ISO’s demand forecast, operating reserve, and replacement reserve requirements for the next operating day. The analysis covers supply offers, external transactions, demand bids for dispatchable asset-related demand, unit-availability information, and ISO demand forecast information, including the deviation between the ISO demand forecast and the sum of cleared demand bids and decrement bids used in the initial commitment.
The control room operators use the Current Operating Plan (COP) capacity analysis information, interchange scheduling software, Operator Information System (OIS), real-time generation (RTGEN), and real-time unit commitment (RTUC) displays to make decisions on declaring Minimum Generation Warning or Emergency.
Reference: SOP-RTMKTS.0050.0010—Perform Reserve Adequacy Assessment
The ISO posts Minimum Generation Warning declarations on its website calendar to notify external participants of the warning. If the ISO declares a Minimum Generation Warning for a period spanning multiple days, it reflects the event in the ISO web calendar for the subsequent day. Please subscribe to the emergency operating system notices to receive email alerts on abnormal operating system conditions. The ISO may take the following actions to mitigate a Minimum Generation Emergency, making exceptions for reliability or transmission outages:
If these actions do not adequately mitigate the Minimum Generation Emergency condition, the ISO will declare a Minimum Generation Emergency event for all New England.
Reference: Minimum Generation, Procedure CROP.25005
The ISO posts Minimum Gen Emergency declarations on its website calendar to notify external participants of the emergency. If the ISO declares a Minimum Generation Emergency for a period spanning multiple days, it reflects the event in the ISO web calendar for the subsequent day.
Declaring a Minimum Generation Emergency should occur on the hour to promote equity between external transaction cuts and generation reductions. However, the declaration may also be made within the hour, if necessary, to respond to sudden events.
In addition to actions listed for Minimum Generation Warning, the ISO may take the following actions to restore the system to normal operating conditions, making exceptions for reliability or transmission outages:
The ISO system operator will allow redeclarations of emergency minimum limits for equipment stability or other operating limits.
Reference: Minimum Generation, Procedure CROP.25005 and CROP.36002 Redeclarations
A Minimum Generation Emergency can be cancelled when the projected difference between the sum of fixed external transactions on the non-CTS interfaces that cleared the Day-Ahead Energy Market and the ecomin limits of all on-line generators is greater than 100 MW of the projected demand and increasing and a recurrence is not expected.