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Brett Wangen, Vic Howell, & Dede Subakti

POTF Recap 2/26-27 POTF Meeting – Salt Lake City. Brett Wangen, Vic Howell, & Dede Subakti. Objectives. Review SOL Methodology fundamentals Review current industry state New Paradigm Requires New Way of Thinking Recap What the POTF Has Agreed Upon

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Brett Wangen, Vic Howell, & Dede Subakti

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  1. POTF Recap 2/26-27 POTF Meeting – Salt Lake City Brett Wangen, Vic Howell, & Dede Subakti

  2. Objectives • Review SOL Methodology fundamentals • Review current industry state • New Paradigm Requires New Way of Thinking • Recap What the POTF Has Agreed Upon • Map Path Operator Duties to the New Paradigm • Phase II – Review of outstanding issues • Phase III – Solutions

  3. SOL Methodology Context Fundamental concepts from the SOL Methodology serve as a foundational context for the POTF efforts: Ahead of time: • “The ultimate task of TOPs and the RC is to continually assess and evaluate projected system conditions as Real-time approaches with the objective of ensuring acceptable system performance in Real-time.” (Purpose section p.5) • “Establishing operating limits such as SOLs and IROLs, scheduling limits; and ensuring plans, processes, and procedures are developed to prevent and to mitigate instances of exceeding SOLs and IROLs are a few of the means by which acceptable system performance can be achieved.” (Purpose section p.5)

  4. SOL Methodology Context Real-Time: • “In the WECC RC Area, the BES is expected to be operated such that acceptable system performance is being achieved in both the pre- and post-contingency state, regardless of the tools TOPs have available.” (Minimum Acceptable System Performance Section, p.6) • “TOPs may use Real-time tools or rely on prior studies, provided that those studies demonstrate acceptable BES performance for the current or expected system conditions.” (Minimum Acceptable System Performance Section, p.6)

  5. What is Acceptable System Performance? SOL Methodology Item #3 p.6: • Pre-Contingency: Acceptable system performance for the pre-Contingency state in the Operations Horizon is characterized by the following [NERC Standard FAC-011-2 R2.1]: • The BES shall demonstrate transient, dynamic and voltage stability. • All Facilities shall be within their continuous Facility Ratings and thermal limits (Refer to illustration in Appendix II). • All Facilities shall be within their pre-contingency voltage limits. • All Facilities shall be within their stability limits.

  6. What is Acceptable System Performance? SOL Methodology Item #4 p.6: • Post-Contingency [SCs]: Acceptable system performance for the post-contingency state for Single Contingencies (SC) in the Operations Horizon is characterized by the following (NERC Standard FAC-011-2 R2.2): • The BES shall demonstrate transient, dynamic and voltage stability. • All Facilities shall be within their applicable short-term Facility Ratings and thermal limits. (Refer to illustration in Appendix II). • All Facilities shall be within their post-contingency voltage limits. • All Facilities shall be within their stability limits. • Cascading or uncontrolled separation shall not occur.

  7. Acceptable System Performance and SOLs SOL Methodology Item #2 p.6 • “If any of the acceptable pre- or post-contingency system performance criteria stipulated in this Methodology are not being met, an SOL is being exceeded.” • Key concept => Unacceptable system performance equates to SOL exceedance • SOL exceedance occurs when acceptable system performance is not happening in real-time operations

  8. SOL Methodology Context • According to the SOL Methodology, acceptable pre- and post-Contingency performance is the ultimate objective. • SOLs are a means to an end – not the end itself. • Ultimate reliability objectives: • To ensure that Facility Ratings and voltage limits are not exceeded in both the pre- and post-Contingency state • To ensure that stability limits are not exceeded in the pre-Contingency state. Pre-Contingency stability limits are established to ensure pre- and post-Contingency BES stability.

  9. Where are we as an industry? • How TOPs accomplish these reliability objectives depends on their tools and study practices and how they think: • Study practices and tools vary widely: • Some entities do not have real-time tools, or they have – but do not use – real-time tools for operations • Some entities have/use RTCA but have no real-time stability tools • Some entities have and use real-time tools (RTCA, transient stability, voltage stability)

  10. Where are we as an industry? No real-time tools in use for operations: • Entities must run studies ahead of time and establish SOLs to ensure acceptable pre- and post-Contingency thermal, voltage, and stability performance • Seasonal SOLs, pre-determined canned SOLs for outage scenarios, etc. • Entities monitor operations within pre-defined SOLs for pre- and post-Contingency thermal, voltage, and stability performance • This is where many TOPs in WECC are today • This approach is consistent with TOP-007-WECC-1, MOD-029a, and current Western practices & thinking

  11. Where we want to be as an industry? Full suite of real-time tools (state estimation, RTCA, voltage stability, and transient stability): • Entities can use prior studies to identify potential thermal, voltage, and stability issues that might be encountered in real-time, and • Establish operational plans in case these conditions are encountered in real-time. • There is no need to establish thermal or voltage “SOLs” ahead of time and operate within them in real-time.

  12. Where we want to be as an industry? CONTINUED: • Stability limits can be established ahead of time with the understanding that they would be updated in real-time. • Entities rely on full suite of real-time tools for acceptable pre- and post-Contingency thermal, voltage, and stability performance. • TOP-007-WECC-1, MOD-029a, and historical practices/thinking may still be a barrier to fully going this route, however.

  13. What is the best way? • The most accurate way of achieving the ultimate reliability objectives (ensuring acceptable pre- and post-Contingency system performance) is through the use of real-time tools and information. • Arguably, the only reason to operate within SOLs established in prior studies is because of the inability to ensure acceptable system performance with real-time tools and information.

  14. New Paradigm = New Thinking • The new paradigm requires a new way of thinking about ensuring reliability. • This new way of thinking may require changes to historical study practices.

  15. Current Way of Thinking • Run prior studies (seasonal studies, outage studies, near-term studies) to determine “the SOL” – seasonal SOLs, canned SOLs for prior outages, near-term SOLs, etc. • “The SOL” is an operating limit (typically MW flow values on WECC Paths and other “paths”) intended to ensure pre- and post-contingency acceptable system performance for thermal, voltage, transient planning criteria, transient stability, and voltage stability. • For WECC Paths, set TTC to be equal to the Path SOL (per MOD-029a).

  16. Current Way of Thinking (continued) • Operate within those previously determined SOLs in real-time, regardless of when they were established or what real-time tools indicate. Some SOLs could be very old. • SOL exceedance (for TOP-007-WECC-1 paths and otherwise) occurs when these previously defined Path SOLs are exceeded in real-time operations. • Currentway of thinking summary: Focus => What is the SOL? • The goal => determine “the SOL” ahead of time and stay within in it in real-time operations

  17. New Way of Thinking • Run studies against projected system conditions (seasonal studies, outage studies, near-term studies): • To determine reliability issues that could be encountered and thus need to be prepared for. • To identify stability limits (even if other limitations are encountered at lower transfer levels). • To determine Transfer Capability/TTC values. • To establish operating plans based on those studies that can be implemented in real-time as necessary based on real-time tool indications.

  18. New Way of Thinking (continued) • Use real-time tools and information and prior operating plans and procedures to ensure acceptable pre- and post-Contingency performance. • SOL exceedance occurs when acceptable pre orpost-Contingency system performance isn’t happening in real-time as indicated by real-time tools and information. • New way of thinking summary: Focus => Know what & where IROLs and stability limits are, and utilize operating plans/procedures and congestion management tools to achieve acceptable system performance. • The goal => acceptable system performance in real-time operations as indicated by real-time tools.

  19. New Way of Thinking – What NERC Wants • This new way of thinking is consistent with NERC CEO, Gerry Cauley’s 9/13/2012 letter to then WECC CEO Mark Maher: • “As these discussions continue NERC suggests that you also review the concept of Path Ratings and whether, as the Western Interconnection has become more highly interconnected, the Path Rating and Path Operator concept, along with the use of nomograms, still has merit for real-time operations.” • “Other Interconnections do determine Flowgate limits for purposes of interchange scheduling, but rely more fully on RTCA for real-time operating reliability.”

  20. POTF Agreed On The Following: • SOL and Transfer Capability/TTC are currently combined. In the new paradigm SOLs and Transfer Capability/TTC will be decoupled. • The “Path SOL” concept goes away: • While Facility Ratings and voltage limits pre- and post-Contingency are always SOLs, a Path itself does not have an SOL. The only time the Path itself has an SOL is when the Path happens to coincide with a monitored stability limit. • Instead, a Path has a Transfer Capability or Total Transfer Capability (TTC) as defined in the NERC Glossary of Terms

  21. POTF Agreed On The Following: Transfer Capability – from the NERC Glossary of Terms • The measure of the ability of interconnected electric systems to move or transfer power in a reliable manner from one area to another over all transmission lines (or paths) between those areas under specified system conditions. The units of transfer capability are in terms of electric power, generally expressed in megawatts (MW). The transfer capability from “Area A” to “Area B” is not generally equal to the transfer capability from “Area B” to “Area A.”

  22. POTF Agreed On The Following: Total Transfer Capability (TTC) – from the NERC Glossary of Terms The amount of electric power that can be moved or transferred reliably from one area to another area of the interconnected transmission systems by way of all transmission lines (or paths) between those areas under specified system conditions.

  23. POTF Agreed On The Following: • Transfer Capability or TTC is not an SOL • Exceeding an established Transfer Capability or a TTC in real-time does not constitute SOL exceedance • SOL exceedance occurs when acceptable pre- or post-Contingency system performance is not happening in real-time operations as indicated by real-time tools • Operators should monitor actual Path flow against pre-determined TTC values to provide operator awareness of when reliability issues might be expected to occur

  24. What About the Path Operator? What about current Path Operator duties? Which Path Operator duties need to persist in the new paradigm? The Path Operator duties include the following: • Runs transfer analysis studies ahead of time to determine the Path SOL. • Allocates the Path SOL and scheduling limits among TOPs who operate Facilities on that Path. • Makes adjustments to the Path SOL in response to real-time events. • Submits Path derates (i.e., Path SOLs) to the RC for the daily Path Report • Is responsible for mitigating Path SOL exceedances. • Gets the NERC fine when a TOP-007-WECC-1 Path is exceeded for longer than 30 minutes.

  25. What About the Path Operator? The following Path Operator activities still need to occur, but they look different under the new paradigm: • Current ParadigmItem #1: Runs transfer analysis studies ahead of time to determine the Path SOL. • New Paradigm: • For TTC – Run transfer analysis studies ahead of time to determine the Path TTC. • For Reliability – Run transfer analysis studies ahead of time to determine stability limits and to identify thermal and voltage limitations that could be encountered.

  26. What About the Path Operator? • Current ParadigmItem #2:Allocates the Path SOL and scheduling limits among TOPs who operate Facilities on that Path. • New Paradigm: • For TTC – Allocates the Path TTC among TOPs who have TTC Facilities on that WECC Path. • For Reliability – N/A

  27. What About the Path Operator? • Current ParadigmItem #3:Makes adjustments to the Path SOL in response to real-time events. • New Paradigm: • For TTC – Make adjustments to the Path TTC in response to real-time events. • For Reliability – Entities rely on real-time tool indication for operating reliability. Implement congestion management procedures and/or tools as appropriate.

  28. What About the Path Operator? • Current ParadigmItem #4:Submits Path derates (SOLs) to the RC for the daily Path Report • New Paradigm: • For TTC – Submits Path TTCs for the daily Path Report. Project underway to integrate the Path Report into COS. Whomever determines this TTC value submits the data to COS via UI or API. • For Reliability – TTC report serves as awareness of reliability issues that could be encountered at certain transfer levels.

  29. What About the Path Operator? • Current ParadigmItem #5: Is responsible for mitigating Path SOL exceedances. • New Paradigm: Paths do not have SOLs. SOL exceedances(as indicated by real-time tools) to be mitigated by the most appropriate or effective means: • With internal congestion management tools (CAISO and BPA have these), and/or • Locally according to operational plans and procedures, or Op Guides, and/or • With interconnection-wide congestion management tools administered by Peak RC.

  30. What About the Path Operator? • Current ParadigmItem #6:Gets the NERC fine when a TOP-007-WECC-1 Path is exceeded for longer than 30 minutes. • New Paradigm: TOP-007-WECC-1 retired or significantly modified. Fines associated with SOL or IROL exceedances will be consistent with other TOP or IRO Reliability Standards.

  31. Phase II – Remaining Issues Look at these from the perspective of the current paradigm and from the new paradigm: • What is the role of Path Ratings in the Operations Horizon? • TTC still needs to be determined. TTC for WECC Paths needs to be allocated among TTC Facilities that comprise the Path. Who does that? How? • TOPs need a way to ensure acceptable system performance in real-time operations. How do TOPs do that if they don’t have real-time tools? Can we move to the new paradigm without TOPs having RTCA? • What does it mean to be in an “unknown operating state”? How is it addressed currently and in the new paradigm?

  32. Phase II – Remaining Issues • How do nomograms fit in to the new paradigm? • Can we move to the new paradigm without an interconnection-wide congestion management tool? • Can we move to the new paradigm while TOP-007-WECC-1 and MOD-029a are still in effect? • What needs to be in place before we can retire TOP-007-WECC-1?

  33. Phase III - Solutions Issue #1 – Do WECC Path Ratings play a role in the new paradigm? Discussion & Solutions: • No – WECC Path Ratings do not play a role in operations. The WECC Path Ratings concept is applicable to the planning horizon but not the operations horizon. • Yes – WECC Path Ratings serve as a TTC cap for WECC Paths. • Other Options?

  34. Phase III - Solutions Issue #2 – TTC still needs to be determined: • Transfer analysis studies need to be run throughout the operations horizon to determine TTC for the WECC Path (seasonal through near-term sub-horizons). • TTC for WECC Paths may need to be allocated among TTC Facilities that comprise the Path (Path 49 for example) • TTC determination is a TOP requirement per MOD standards. • Transfer analysis studies need to be run throughout the operations horizon to determine stability limits – even if voltage or thermal constraints are encountered at lower transfer levels (big change for some)

  35. Phase III - Solutions Issue #2 – Discussion & Solutions: • For each WECC Path, set up agreements for an entity to establish TTC for the “parent” WECC Path and to allocate those TTCs to the “children” ATC Paths. • Agreements and contracts determine who/when/how/how often these TTC values will be established. • Peak Reliability may be able to provide these services. May require delegation agreements. • May need establish a mechanism (tool) for communicating and allocating TTC values

  36. Phase III - Solutions Issue #2 – Discussion &Solutions: • For Paths that connect multiple TOPs – multiple TOPs establish TTC for the same Path. The lower TTC wins out. • TOPs establish agreed upon process for TTC determination for common paths. • For Paths within a single TOP Area, the TOP establishes TTC for the parent Path and allocates to children Paths. • Peak RC to calculate wide-area voltage and transient stability limits for shorter-term sub-horizons (including real-time). This will happen for reliability. • End goal – to have agreements and understanding of who calculates TTC for every ATC Path in WECC.

  37. Phase III - Solutions Issue #3 – TOPs need a way to ensure acceptable system performance in real-time operations. • How do TOPs do that if they don’t have real-time tools? • Can we move to the new paradigm without TOPs having RTCA? Discussion & Solutions: • RC hosted advanced apps always an option

  38. Phase III - Solutions Issue #4 – What does it mean to be in an “unknown operating state”? How is it addressed currently and in the new paradigm? • TOP-004-2 R4 states: “R4: If a Transmission Operator enters an unknown operating state (i.e. any state for which valid operating limits have not been determined), it will be considered to be in an emergency and shall restore operations to respect proven reliable power system limits within 30 minutes.”

  39. Phase III - Solutions Issue #4 (CONTINUED): • This issue will be addressed as part of NERC TOP/IRO standard revision initiative. • From the NERC Reliability Concepts Document (2007): “Therefore, system operators must operate “where they have studied” so they will know where they may land following a contingency. This means they may need to take certain actions to reposition the system into a state that has been studied and shown to result in acceptable performance following a credible contingency.” • Discuss the relevance of this statement in light of the use of real-time tools

  40. Phase III - Solutions Issue #4 – Discussion & Solutions: • Current paradigm: • Stress a path until unacceptable post-Contingency performance is encountered, or up to the Path Rating, whichever is lower. Add margin of 5% for single Contingencies or 2.5% for multiple Contingencies • Anything beyond that point represents an “unknown operating state”

  41. Phase III - Solutions Issue #4 – Discussion & Solutions: • New Paradigm: • If in prior studies, stressing stops at 1000 MW, is Path flow of 1001 MW considered an “unknown operating state”? • SOL Methodology requires TOPs to stress the system to “reasonably expected maximums” to see if voltage stability limits exist • Potential solution – model major WECC Paths as a scenario in Peak’s Voltage Stability Analysis tool • What about transient stability?

  42. Phase III - Solutions Issue #5– How do nomograms fit in to the new paradigm? Discussion: • Nomograms are created ahead of time to predict a safe region where by operating inside the region would lend itself to an acceptable pre- and post- contingency system performance state. • In the real time, nomograms are no different than “Path SOLs”. They are merely an attempt to describe interaction between one Path SOL and the other Path SOLin order to maximize the usage of a particular Path. • If real time tools can sufficiently show acceptable pre- and post- contingency operation, then nomogramsarguably are no longer needed as operating limits (SOLs).

  43. Phase III - Solutions Issue #5– Discussion (CONTINUED): • Nomogramscould still be developed in planning, seasonal assessment to illustrate the expected interaction between multiple paths. • Nomogramscould also be used to show interaction between multiple ATC path that is then used for TTC coordination (how would this work?) Possible Solutions: • Nomogramsgo away for the Operations Horizon • Nomograms help establish TTCs (how?) • Nomograms provide awareness of when to watch for specific reliability issues…no different than monitoring TTC against actual Path Flows. • Other ideas?

  44. Phase III - Solutions Issue #6– Can we move to the new paradigm without an interconnection-wide congestion management tool? Discussion & Solutions: • Current paradigm & no ECC (current state) • Current paradigm & ECC • New paradigm & no ECC • New paradigm & ECC

  45. Phase III - Solutions Issue #7– Can we move to the new paradigm while TOP-007-WECC-1 and MOD-029a is still in effect? Discussion & Solutions: • Yes – because… • No – because…

  46. Phase III - Solutions Issue #8 – What needs to be in place before we can retire TOP-007-WECC-1? Discussion & Solutions:

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