Overview of February 2021 Arctic Weather

Markets Subcommittee 11, 2021 Executive

Summary • The effects of a February 2021 arctic weather event were felt across MISO and neighboring systems

• MISO’s procedures worked as drilled and designed, limiting load curtailment in the MISO footprint to a regional event lasting approximately two hours and a handful of local events

• Experiences across the highlight the urgency to complete the work summarized in MISO’s Reliability Imperative

2 MISO was well positioned for the arctic weather due to on- going actions and leveraging operating procedures before and during the event ARCTIC EVENT MISO regularly coordinates with our , 2021 neighbors during these events and during ▪ Local Transmission normal operations PRE-EVENT Emergency – Western Load Pocket (SE Texas) ▪ Issued , 2021 ON-GOING Informational Advisories & Cold ▪ Local Transmission Emergencies Coordinated Weather Alert SYSTEM ▪ Seasonal ▪ Western Load TOPOLOGY ▪ Daily coordination Assessments with neighbors Pocket (SE Texas) ▪ Highly inter- () ▪ North-Central ▪ Committed connected grid Louisiana ▪ Winter Readiness additional gas across 15 states ▪ Transmission System Workshops generation early to and Emergency – South- ▪ Emergency secure fuel supply Central Illinois ▪ Diverse generation Procedure Drills ▪ Declared mix ▪ Maximum Generation Conservative Event Step 5 – South ▪ Relationships with Operations Region seams partners

3 The arctic weather pattern directed extreme cold across the Plains, Midwest and South

Advance Preparation • Conducted Winter Readiness Workshops • Issued Informational Advisories • Issued a Cold Weather Alert • Committed additional generation well in advance of need • Extended the start/stop times for generation resources to avoid start failures due to cold weather • Confirmed planned outage and return-to-service dates/times for generation and transmission outages

4 In the South, many cold temperature records were broken, driving winter peak loads close to peak levels MISO South Load Peaks

Winter Load Peaks 2021: 31.6 GW All-Time: 32.1 GW Set Jan 17, 2018

Summer Load Peaks 2020: 31 GW All-Time: 32.7 GW Set Aug 15, 2015

5 As the cold weather continued, approximately 40% of installed resources were unavailable, leading to emergency declarations

Daily Average (GW) Unplanned Generation Outages , 2021

SYSTEM-WIDE

~33% of fleet

~7% of fleet

*Unplanned includes forced outages and derates 6 Data as of , 2021 in CROW Outage system Unprecedented flows across our system that aided the interconnection also contributed to the need for emergency declarations Manitoba Hydro

Ontario MISO Net Scheduled PJM Southwest Power 1.7 8.0 Interchange Pool Interconnection (GW) 1.7

Associated Electric Cooperative Southeastern Incorporated 0.8 Regional Transmission Electric Reliability Planning Region Council of Texas

Image represents average flows into, out of and through MISO over 3 days (February 15-17, 2021) 7 RDT = Regional Dispatch Transfer, which has a North-South limit of 3 GW When the system is constrained, MISO will activate the appropriate emergency procedure with directed load curtailment always as the last resort

Local Transmission Emergency

Declared when MISO expects it will not be able to mitigate operating limit conditions using normal procedures in a timely fashion

Transmission Emergency Transmission System Emergency Declarations Declared to mitigate the potential of violating a limit that could lead to instability, uncontrolled separation, or cascading outages impacting the Bulk Electric System

8 Through the operational challenges, MISO’s procedures worked, limiting directed load curtailment to a two-hour regional event and local events

Transmission System Emergency 2/16/21 Morning Peak Directed 130 MW load curtailment east of St. Louis

Maximum Generation Event, Step 5 2/16/21 Evening Peak Directed 700 MW load curtailment in the South Region Local Transmission Emergency 2/15/21 Morning Peak Directed 800 MW load curtailment in the Western Load Pocket Transmission System Emergency 2/16/21 Morning Peak Directed 1000 MW load curtailment in the Acadiana Area

Local Transmission Emergency 2/16/21 Morning Peak Directed 300 MW load curtailment in the Western Load Pocket

9 9 During a three-day period, MISO managed multiple independent and interdependent challenges across the footprint

Feb Actions Feb 13 Feb 14 Feb 15 Feb 16 Feb 17 Feb 18 Feb 19 Feb 20 8-12

MISO Footprint Informational Advisories Daily coordination with neighbors Committed additional gas generation Cold Weather Alert Conservative Operations MISO North Maximum Generation Event 1b MISO Central Local Transmission Emergency (LTE) - Ameren Transmission System Emergency (TSE) Maximum Generation Event 1b Transmission Loading Relief (TLR) 5A MISO South Capacity Advisory Maximum Generation Alert Maximum Generation Warning Maximum Generation Event 1a Maximum Generation Event 2a Maximum Generation Event 2c Maximum Generation Event 5 LTE - Western Load Pocket (SE Texas) LTE - Arkansas LTE - Murray Hydro LTE - CLEC, EES, LAFA, LEPA TSE TLR 5B/a TLR 5A

10 Duration of load curtailment and recovery associated declarations shown in red 10 Duration of declarations shown in blue Transmission-related load directives were driven by generation and transmission outages and real-time thermal overloads

Description Load Total Drivers Reason Directed Conditions Curtailed Duration of Necessary for Outage* Restoration

Local 800 MW 16 hours • Loss of generation Overloads and Transmission • Loss of multiple transmission possible temporary Emergency - lines in Western Load Pocket Interconnection Western Load Reliability Pocket (SE Texas) Operating Limit • Forced generation Local 300 MW 5 hours 40 • Loss of generation Voltage and • Transmission Transmission minutes • Loss of multiple transmission thermal concerns outages Emergency - lines in Western Load Pocket returned to Western Load service Pocket (SE Texas) • Load levels Transmission 1000 MW 4 hours 5 • Extreme East-to-West Flows Cascading outages decreased System minutes nearing the operating limit on key Emergency - 500kV line Louisiana • Generation and transmission outages due to weather Transmission 130 MW 7 hours • Extreme East-to-West bias Multiple overloads • Transmission System causing flows on a 345kV line to Loading Relief Emergency – exceed 150% post contingent • Generation Central Illinois creating a possible temporary available to Interconnection Reliability manage all Operating Limit constraints

11 * Load was incrementally released to return to service as conditions warranted On February 16, a Maximum Generation Event Step 5 and directed load curtailment was triggered by lost generation

February 13-15 February 16, February 16, February 16, 12 a.m. EST 6:35 p.m. EST 7:40 p.m.EST Cold Weather Alert (2/13) Conservative Operations (2/14) Max Gen Max Gen Event Max Gen Warning (MISO Step 2c South Capacity Advisory (2/15) Event Step 5 South) (MISO South) (MISO South) South Max Gen Alert (2/15)

• Arctic weather pattern brought • An increase in • Generation trouble began to emerge as heavy snow and ice accumulation, unplanned 2500 MW became unavailable by 4 p.m. followed by cold temperatures generation outages, • Initiated public appeals for conservation • Available generation and transmission losses, • With grid stability in danger, no potential transmission issues capacity uncertainty, additional imports available, and not identified; additional generation and risk of additional enough available energy to meet committed outages demand, MISO operators directed Load • MISO maintained ongoing Balancing Authorities to collectively communication with curtail 700 MW of load to avoid wide- members, neighbors and spread cascading outages regulators

Alerts Warnings Events

12 An increase in unplanned generation outages and the risk of more contributed heavily to emergency declarations, including the Maximum Generation Event Step 5

3.9 GW

7.2 GW

Total unplanned 6.4 GW 13.6 GW 17.5 GW 18.0 GW 16.8 GW Percentage of installed 16% 33% 42% 44% 41% capacity** (41.3 GW)

Chart reflects data as it resided in the CROW Outage system on March 1, 2021

*Unplanned: Forced plus derates 13 ** Installed capacity is the amount that cleared in the Planning Resource Auction plus internal MISO generation that qualified for the 20-21 planning year Emergency pricing was activated in alignment with the appropriate maximum generation declarations

Locational Marginal Pricing across MISO at 7:45 p.m. (EST) February 16, 2021

14 This event serves to illustrate the urgency to complete the work summarized in MISO’s Reliability Imperative

• Availability is less than expected when conditions are tight, and the significant drivers (e.g., winterization, fuel assurance) are unique to (Addressed through Market Redefinition: Resource Adequacy Construct and Accreditation) • Sufficient transfer capability within and between regions is critical to enabling the advantages of regional diversity (Addressed through Long Range Transmission Planning) • Assessment of uncertainties is critical for adequate and efficient commitment and real-time operational response (Addressed through Operations of the Future) • Resource adequacy evaluation in constrained areas is necessary (Addressed through Market Redefinition: Resource Adequacy)

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