Enhanced Curtailment Calculator (ECC) Task Force Update

1. Enhanced Curtailment Calculator (ECC)Task Force Update Presentation to the Joint Guidance Committee Meeting May 31, 2012

2. Enhanced Curtailment Calculator, ECC ECC Task Force Members • OC - Brenda Ambrosi – BC Hydro • OC - Carl Dobbs – WAPA CA • OC - David Lunceford - CAISO • MIC - Raj Hundal – Powerex • MIC - David Lemmons – Xcel (Vice Chair) • MIC - Doug Reese – Tri-State • WECC RC - Linda Perez (Chair) • WECC RC - Jeff Sundvick (acting Chair)

3. ECCTF & UFAS Roles • Process to determine which nominated elements can be included in the ECC Tool. (ECCTF) • Process to use the Qualified Devices during a UFMP. (UFAS) • Ability to add elements on the fly. (ECCTF) • Modeling of specific elements (including source/sink points) for TDF calculation. (ECCTF, e.g. continue using seasonal WECC planning model with monthly updates relative to any 100kv or higher element. Or, use WWSM, six-week uploads with real-time updates.)

4. ECCTF & UFAS Roles (cont) • Determination of minimum TDF and physical impact thresholds and how they are used for curtailment evaluation. (UFAS is addressing, ECCTF can review) • Impacts, quantification, and treatment of non-tagged system uses. (ECCTF) • Training process for WECC RC and WECC BA on new procedures. (ECCTF) • Process to update and provide real time information on outages and disturbances. (ECCTF)

5. Enhanced Curtailment Calculator, ECC • Objective The ECC project seeks to improve the Reliability Coordinators (RCs) ability to monitor the Western Interconnection Bulk Electric System such that they: • Better understand the contributing factors to congestion on the Bulk Electric System. • Are better equipped to assign relief obligations during periods of transmission congestion that are more representative of those actually contributing to the congestion.

6. Enhanced Curtailment Calculator, ECC • Problem Statement - The ECC project was initiated in response to WECC members seeking to enhance the tools used by the RC to monitor the operation of the Bulk Electric System. - The area identified as needing improvement is the ability to identify and then take appropriate actions to reduce loading on facilities when the facilities are at or very near their System Operating Limit (SOL).

7. Enhanced Curtailment Calculator, ECC • Problem Statement (cont.) • The current congestion tool, webSAS, is only used to calculate curtailment responsibility on six Qualified Transfer Paths. - It does not calculate tag curtailments with respect to transmission priority, account for sub-hourly or untagged schedules, determine generation for potential redispatch, or calculate distribution factors based on current system conditions and topology.

8. Enhanced Curtailment Calculator, ECC • Problem Statement (cont.) • As increased amounts of variable generation penetrate the interconnection it will be necessary for these calculations to interface with SCADA data to provide reliable analysis in near real-time. • Coordinate planning and real-time models for evaluation of congestion and contingency analysis.

9. Enhanced Curtailment Calculator, ECC • Scope The proposed ECC would calculate impacts on many more paths or distinct elements; potentially all rated paths; and some additional, currently unrated paths. The proposed enhancements would allow: • Real-time updates of transmission system data to include actual generation and outages (currently the data is updated twice annually). • A more granular model of the physical system.

10. Enhanced Curtailment Calculator, ECC • Benefits • Accounts for all tagged and untagged system flows. • Allows for real-time updates of transmission system data to include actual generation and outages. • Facilitates pro forma tariff compliance by transmission providers to perform pro rata curtailment calculations based on transmission and/or generation priority. • Provides greater accuracy and system topology for reliable congestion management decisions by RCs and Transmission Operators.

11. Enhanced Curtailment Calculator, ECC • WECC RC View of Current Situation • The continued evolution of the NERC Reliability Standards has placed a greater emphasis on RC’s role in ensuring the reliability and integrity of the Bulk Electric System (BES). • Recent changes to WECC RC’s SOL Methodology for the Operations Horizon place more emphasis on monitoring individual equipment/facility SOLs.

12. Enhanced Curtailment Calculator, ECC • WECC RC View of ECC Tool Benefits The ECC tool for managing congestion throughout the interconnection would: • Enhance RC’s ability to identify sources that could be contributing to actual and anticipated congestion in a specific area. • Improve RC’s ability to evaluate mitigation plans to determine their viability, and provide a method for determining the most effective and equitable mitigating actions available to prevent and manage congestion.

13. Enhanced Curtailment Calculator, ECC • WECC RC View of ECC Tool Benefits • Improve RC’s ability to communicate and coordinate the most effective mitigating actions among affected entities. • While the ECC tool is not expected to be able to solely mitigate an actual IROL exceedance within 30 minutes, it would be a powerful WECC RC management tool to prevent an IROL from ever being exceeded in the first place.

14. Enhanced Curtailment Calculator, ECC

15. David Lemmons Senior Manager, Market Operations P: 303-571-6520 David.f.lemmons@xcelenergy.com Questions?