During the February 1, 2023, Planning Subcommittee (PSC) meeting, MISO presented the study results of the MTEP22 Extreme Events Analysis. MISO is requesting Stakeholder feedback on the Extreme Event results presented.
Please provide feedback by March 1.
Transmission Owners Sector Feedback on Extreme-Event Analysis.
March 1 2023.
During the February 1, 2023 Planning Subcommittee (PSC) meeting, MISO presented the study results of the MTEP22 Extreme Events Analysis.
The comments below are submitted by the Transmission Owners Sector (Owners or TOs).
(1) The Owners would like MISO to include LRTP lines expected to be double-circuited in their extreme-event analyses.
(2) The Owners would like MISO to model loss of gas supply to a region or area of gas plants not having gas supply.
(3) The Owners would like MISO to consider the impacts of extreme cold weather on gas supply.
(4) The Owners would like MISO to model loss of large amounts of wind or solar ("droughts") in extreme event analyses. Periods of calm, cloudy weather or even a snowstorm can present new reliability risks to MISO’s renewable generation fleet.
(5) The Owners would like MISO to model at least 10 years out for extreme events to show the greater effects of wind or solar "droughts". This is due to the fact a loss of wind now may only result in loss of 20 GW of generation, and in the future loss of wind may result in loss of 40 GW or more of generation.
(6) The Owners would like MISO to model the P7 events from double-circuited LRTP lines in MTEP analyses.
(7) The Owners would like MISO to continue to honor Local Planning Criteria (LPC) in extreme-event analyses.
(8) The Owners request MISO to post the contingency files used for the MTEP extreme event analysis to the MISO ShareFile similar to the Category P1-P7 contingency files used for MTEP.
(9) The Owners request MISO to expand the narrative discussion of the analysis performed and the results of the TPL-001-5 Extreme Event 3.a.i. gas pipeline outage contingencies in the MTEP CEII appendices.
Comments of the MISO Environmental Sector on the MTEP Extreme Events Process Overview
The MISO Environmental Sector appreciates the opportunity to comment on the results of the MTEP22 Extreme Event analysis presented at the February 1, 2023 meeting of the Planning Subcommittee. The contingency results of MISO’s Extreme Events analysis do not reflect what MISO retail customers have experienced in the recent past. Accordingly, it appears that MISO’s Extreme Events Process is flawed and must be revised to help the transmission owners appropriately prepare for extreme events. Below we identify the anomalous results, at least one factor causing those results, and suggestions for improving MISO’s Extreme Events Process.
MISO’s Results Do Not Reflect Reality:
On slide 6, MISO’s presentation shows 315 potential cascading events occurring in the West Region, compared to only 18 for the South Region. Moreover, slide 8 shows that all of the cascading events in the South Region were caused by E1 contingencies, the outage of two BES elements. None of the cascading events in the South Region were caused by extreme weather (E3Aiv). (Indeed, none of the cascading events anywhere in the MISO footprint were caused by extreme weather. See Slide 7.)
In reality, the South Region has experienced the following contingencies in the recent past:
loss of a tower line (E2A) during Hurricane Ida;
hurricanes (E3Aiv) like Hurricane Laura, Delta, and Zeta;
loss of a large load or major load center (E2E) like the loss of New Orleans during Hurricane Ida; and
loss of two generating stations within the same Local Resource Zone (LRZ) (E3A) which assuredly occurred during Winter Storm Uri when 44% of thermal generation was unavailable during the height of the storm.
While we recognize that MISO is attempting to model future extreme events, we would expect the results to, at least somewhat, mirror recent history. Why is it that the West Region showed over 17 times the number of potential cascading events than the South Region even though the South Region has experienced some of the worst reliability in the MISO footprint?
Potential Causes for the Anomalous Results:
Based on a conversation with MISO, we understand that MISO allows the transmission owners (TOs) to identify the extreme event contingencies that should be studied in their footprint. Apparently the TOs in the South Region only asked that MISO study NERC TPL-001 Standard E1 events, or Loss of a Single Generator. This resulted in an artificially low number of cascading events (18) in an area that regularly experiences extreme weather and relies on load shedding to avoid cascading outages. Suggesting that the southern TOs are only concerned about E1 events is belied by their bottom-up filing in MTEP23 where they have requested billions of dollars to address extreme weather events [1].
Recommended Improvements to MISO’s Extreme Events Analysis:
While some of MISO’s TOs are clearly asking MISO to study a range of contingencies, others are intentionally trying to avoid the very contingencies that are most likely to occur within their service territories. MISO should not simply take the TOs’ list of contingencies verbatim but instead should ground truth that list with the recent past incorporating additional contingencies that have been experienced in the area.
For example, we were surprised that none of the cascading outages modeled were caused by extreme weather events. We recommend that, regardless of the TOs’ list of extreme event contingencies, MISO should explicitly call out weather events that may lead to common mode failures in the system where many outages could occur due to the same root cause. Currently forced outage due to cold weather is probably the risk factor most likely to cause a high-impact low-probability event. Recent storms like Winter Storm Uri and Winter Storm Elliott highlight the importance of adequately evaluating extreme events and the impacts to both generation and demand. In particular, coal plants can be on outage due to frozen coal piles. Gas generators can be out due to frozen components, or due to insufficient gas availability due to excessive demand and residential and commercial use being prioritized over electricity generation or due to lack of pipeline pressure because of compressor station failures. While wind and solar units often provide essential support during these times, circumstances can sometimes occur where individual units may also be offline during the same extreme weather situation. At the same time, demand will be high due to the cold, including in the MISO West, East and Central Regions, as they too transition to electric heat. We encourage MISO to evaluate extreme events based on past history and robust guidelines rather than a TO-provided contingency list.
In conclusion, the Environmental Sector appreciates MISO’s efforts to consider extreme events that could lead to cascading outages. However, many consumers throughout MISO have been experiencing regular outages due to extreme weather and those experiences are not reflected in MISO’s Extreme Events Analysis.
[1] For example, Entergy Louisiana Project 23935, the Downstream of Gypsy (DSG) Reliability & Resiliency project justification states, "Improved extreme event resilience path into DSG, which includes the Metro New Orleans area that can be useful in restorations during Hurricane and other extreme weather events." This proposed $164.2 million project would construct a new 27 mile 230kV transmission line from the Waterford substation to the Churchill substation.
Entergy Louisiana's Project 23954, the Amite South Reliability Project Phase 1, is a $1.4 billion project where a new 60 mile 500kV transmission facility with 230kV underbuild would be constructed. This project justification includes, "Improved extreme event resilience Provides two EHV paths between Baton Rouge and Waterford. Location of line provides geographic diversity that can be useful in restorations during Extreme Weather Events."
Entergy Louisiana's Project 23957, the Amite South Reliability Project Phase 2, includes a similar project justification: "Improved extreme event resilience Provides an additional hardened path in the Industrial Corridor, that can be useful in restorations during events like a Hurricane. Reduces risk of extreme event involving Gypsy corridor." This $290 million project includes portions of both 230kV and 500kV transmission installations.
Entergy Louisiana's Project 23959, the Amite South Reliability Project Phase 3, at a cost of $260 million, will include a new 40 mile 230kV transmission line. The project justification states, "Improved extreme event resilience - Provides an additional hardened path into Amite South, that can be useful in restorations during Hurricane and other extreme weather events."
Entergy Louisiana projects:
Entergy Texas' Project 23952, the Southeast Texas (SETEX) Area Reliability Project justification states, "Improved extreme event resilience Location of line provides geographic diversity that can be useful in restorations during extreme weather events like Hurricanes and Winter Storms." The $1.1 billion project includes a 150-mile 500kV transmission line.
Entergy Texas project: https://cdn.misoenergy.org/20230203%20SSPM1%20Item%2003b%20Review%20of%20Proposed%20Reliability%20Projects%20TX627757.pdf
LS Power proposes that MISO consider whether regionally planned transmission projects – such as Long-Range Transmission Plan (or other Multi-Value) Projects – would be more efficient or cost-effective than individual Transmission Owner-proposed projects in reducing the likelihood or mitigating adverse impacts of Extreme Events. We observe that for the MTEP22 Extreme Events study, MISO worked with incumbent Transmission Owners on developing solutions to address resulting system vulnerabilities (as noted on slides 2 and 9 of the 2/1 PSC presentation). This appears to limit MISO to the use of more localized solutions that the Transmission Owners have the authority to propose - and to build or implement themselves. It also precludes MISO’s consideration of regional solutions that could be more cost-effective in the long-term, or could more efficiently address multiple system needs. In either case, since MISO stakeholders are not privy to MISO’s and the TOs’ review of potential fixes, stakeholders will not know whether any regionally planned solutions would have more efficiently or cost-effectively addressed identified vulnerabilities.
For all of the above reasons, LS Power asks MISO to improve transparency by including all MISO stakeholders in the review of Extreme Events and solutions in 2023, rather than presenting the completed Extreme Events analysis to stakeholders for feedback. We also ask that MISO, in its role as the independent regional planning authority, develop and consider more comprehensive solutions that could reduce the likelihood or mitigate adverse impacts of Extreme Events while also addressing other transmission needs.
MidAmerican Energy Company (MidAmerican) recommends MISO expand the narrative discussion of the analysis performed and the results of the TPL-001-5 Extreme Event 3.a.i. gas pipeline outage contingencies in the MTEP CEII appendices that are posted to the MISO ShareFile. MidAmerican believes that MISO is well positioned to perform this type of wide area analysis, and that the results of the analysis are of interest to MISO Stakeholders given recent historical events such as Winter Storm Uri in February 2021 that demonstrate the importance of natural gas supply to electric system reliability.
MidAmerican also requests that MISO post the contingency files used for the MTEP extreme event analysis to the MISO ShareFile similar to the Category P1-P7 contingency files used for MTEP.
The extreme event categories need to include Protection System (PS) Single Point of Point (SPF) under a 3-phase fault. TPL-001-5 table 1 only requires SPF under Single Line to Ground (SLG) Faults to be assessed with required Corrective Action Plans (CAP). The worst case fault location may be dramatically different for SLG vs 3 phase faults. Possible mitigating actions for a SPF 3 phase fault may be similar to what is used to correcting a SPF SLG, but should not be documented as a CAP and obligating the TP to fix. Please include the SPF 3 phase faults as extreme event per Order 867.
ORDER NO. 867 Approving TPL-001-5
Page 15, paragraph 23
improbability of single points of failure in combination with three-phase faults resulting in cascading outages, we determine that it is reasonable to address such occurrences as extreme events only requiring analysis and evaluation of possible mitigating actions designed to reduce adverse impacts.