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ECC Task Force Discussion

ECC Task Force Discussion

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ECC Task Force Discussion

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  1. ECC Task Force Discussion WECC Market Interface Committee 7/15/11 Stephen Beuning, Xcel Energy, 303-571-2711

  2. ECC Task Force • Scope has been established by the chairs of the OC/MIC • Task Force Membership selection underway, complete in August • 3 OC reps: 1 each from ISAS / UFAS / OPS • 3 MIC reps: 1 each from SIS / MIS & at-large • 1 Reliability Coordinator rep

  3. ECC Task Force Scope • ECC design elements: • Calculate and issue curtailment responsibility upon request by the Transmission Provider or the Reliability Coordinator • Enhance the flow calculation methodology • E.g. more granular source/sink • Allow impact calculations for grid elements nominated by transmission providers or the reliability coordinator • Either “n-state” and “n-1 state” limits • Not limited to Qualified Paths • Include untagged flow impact contributions including native/network delivery

  4. ECC Benefits • Consistent method of curtailment calculations • Increased reliability (not limited to Qualified Paths) • Pro forma tariff compliance by transmission providers for pro-rata curtailments based on transmission service priority

  5. ECC relationship to the EIM • If/when an Energy Imbalance Market (EIM) is established in the region, the cost for any related ECC upgrades would be included in EIM market development costs and not allocated through the WECC RC • If developed, the EIM would seek upgrades to the ECC functions in order to support market settlement calculations for energy imbalance

  6. Seams Coordination Tool Conceptual Examples and Discussion

  7. Curtailment priority coordination concept: Loading Unloading Avoid Overflow Priority 0 – If applicable Priority 1 - NS Priority 2 - NH Priority 3 - ND Priority 4 - NW On Deck Priority 5 - NM Priority 6 - NN Priority 7 - F Flowgate Loading Notes: No displacement of same priority transactions except Firm. Firm curtails pro-rata.

  8. Determining curtailment priority of transmission flows The seams coordination tool calculates all components of flow on each grid element. For example with Flowgate “A”: WECC Footprint Flowgate A Tagged Total MWFlow on Flowgate A Untagged

  9. Seams Coordination Tool Say this grid element is congested and needs relief… The tool prepares the following list for the element: Service Transaction MW Transaction IDPriorityof flow on element Tag # x 2 13 Tag # y 2 4 Tag # z 6 20 BA1 – native 7 8 Tag # a 7 2 BA2 – native 7 6 ….. ….. ….. “The Grid” Curtailments are then allocated pro-rata within each service priority bucket up to the necessary amount of relief obligation.

  10. Tool Attributes • Not a state estimator • DC Power Flow Model for fast calculations • Model uses near-current system topology and unit availability information • E.g. in the East: inputs from the SDX & markets • E.g. in the West: design could propose inputs from the EHV Data Pool & markets

  11. Tool Attributes • Generator Sources and Load Sinks are defined in the tool • Monitored Elements are defined in the tool • The tool calculates shift factors • Generator sources to Swing Bus • Swing Bus to Load Sinks • Shift factors are combined to obtain distribution factors from Generator to Load

  12. Tool Attributes • Each Monitored Element has a calculated distribution factor available for any Gen-Load combination • E.g. Eastern Interconnection has ~3000 Monitored Elements • Monitored elements include lines, transformers or interfaces • Monitored elements may include contingent outage (n-1) in the distribution factor calculation • PTDF = system intact distribution factor calculation • OTDF = distribution factor is calculated for assumed loss of a specific contingent element

  13. Tool Attributes • Tagged Flow Impact Calculation • Input: E-TAG source/sink, MW amount and transmission service curtailment priority • Calculation: • Multiply ETAG MW by the distribution factor to derive the flow impact of the tagged delivery on the Monitored Element

  14. Tool Attributes • Untagged Flow Impact Calculation • Inputs: • Intra-BA generator availability or on-line status • BA Net Scheduled Interchange • BA Forecasted Hourly Load • Example calculation (one method): • Available Generators Scaled to BA Net and inferred to BA Hourly Load • Each generator delivery impact on the monitored element summed to determine Untagged Flow Impact • NERC/NAESB working on process improvements through their “Parallel Flow Visualization Tool” project

  15. Tool Attributes • Tool complies a list of MW contribution on Monitored Elements • The list is ranked by curtailment priority

  16. Operations Process with ECC Discussion

  17. Process for Tool Use • Transmission Provider (or RC) recognizes either a direct or an n-1 contingent limit on a grid element • Transmission Provider evaluates amount of congestion relief required and inputs relief request into tool (or RC) • Tool establishes the list of curtailment obligations to meet the requested relief • Within marginal priority bucket is pro-rata (Order 890) • Below-marginal bucket cuts all impacts above minimum impact threshold (e.g. 1MW or 5%)

  18. Policy Issues Discussion

  19. Policy Issues • Along with the technical specifications for the ECC there are associated policy issues • Relationship to UFMP / COPS? • Both model and operations coordination • Retain WECC on-path and off-path steps or combine into a single priority bucket method? • Establish rules for impact prioritization if chained paths include multiple priorities of service (see next slide for illustration)

  20. A 2 5 5 E Non-Firm 5 B F 2 C 7 2 D 2 Z 5 Example of Policy Issue • Transmission Priorities • 1. Secondary • 2. Hourly • 3. Daily • 4. Weekly • 5. Monthly • 6. Non-Designated • Network Resources • 7. All Firm • Point to Point • - Native Load • - Network Service Constraint Policy Example: For the Constraint on C 1. A-Z Schedule treated as Priority 7 2. E-Z Schedule treated as Priority 5 (>minimum% impact on C)

  21. Comments/Discussion

  22. Comment on use of OTDF • UFMP does not consider the post-contingent distribution factor impact in evaluating contribution to potential overloads • Depending on the monitored element and the schedule source/sink, the OTDF calculations can provide more efficient relief (curtailment) calculations

  23. Comment on use of GTL DF • UFMP does not represent specific generators or load sinks and instead uses zonal approximations for sources and sinks • More precise representation of source/sink pairs can provide more efficient relief (curtailment) calculations

  24. END