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SPP Presentation

SPP Presentation. Available Transfer Capability. ATC/AFC Fall 2005. Learning Objectives. Distinguish ATC from AFC Identify the SPP method for calculating ATC Explain the factors included in SPP ATC calculations

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SPP Presentation

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  1. SPP Presentation

  2. Available Transfer Capability ATC/AFC Fall 2005

  3. Learning Objectives • Distinguish ATC from AFC • Identify the SPP method for calculating ATC • Explain the factors included in SPP ATC calculations • Explain the information on OASIS Automation that a tariff administrator uses to evaluate a transmission service request for approval/denial • Explain the selling of non-firm TRM

  4. SPP Determination of ATC • SPP uses a “constrained element” flow-based approach when evaluating transmission service requests. • Flowgates or constrained facilities are typically the limiting facilities in an area, and consist of groupings of network model branches such as lines and transformers. • Response factors are used to determine the impact a reservation request will have on the flowgate. • A minimum of 30 flowgates are evaluated to determine the ATC for a path, selecting the most restrictive flowgate as the basis for calculating ATC • Response factors are re-calculated every hour

  5. Definitions • Available Transfer Capability (ATC) NERC:“A measure of the transfer capability remaining in the physical transmission network for further commercial activity over and above already committed uses”. SPP: “The Available Flowgate Capacity divided by the Transfer Distribution Factor of the flowgate for the path under evaluation”. ATC = AFC/TDF or AFC = ATC X TDF

  6. Definitions • RATC • Recallable ATC – Can be recalled • Non-Firm • NATC • Non-recallable ATC – Cannot be recalled • Firm

  7. Definitions (per SPP) • Available Flowgate Capacity (AFC) • “The available capacity on a flowgate for additional loading for new power transfers determined by subtracting the flowgate base loading, transmission margins, and existing system commitments.” • Total Flowgate Capacity (TFC) • “The amount of power allowed to flow over a defined element set.”

  8. NERC Formula for ATC ATC = TTC – TRM – CBM – Existing Transmission Commitments TTC = Total Transfer Capability TRM = Transmission Reliability Margin CBM = Capacity Benefit Margin

  9. Definitions (per NERC) • Total Transfer Capability (TTC) • “The amount of electric power that can be transferred over the interconnected transmission network in a reliable manner under specific conditions.” • Transmission Reliability Margin (TRM) “That amount of reserved flowgate capacity necessary to ensure that the interconnected transmission network is secure under a reasonable range of uncertainties in system conditions.”

  10. Definitions (per NERC) • Capacity Benefit Margin (CBM) “The amount of flowgate capacity reserved by load serving entities to ensure access to generation form the interconnected systems to meet generation reliability requirements”. • Existing Transmission Commitments • Native and Network Load • Reservations (Those included depends if it is firm or non-firm calculation)

  11. SPP Formulas for ATC/AFC ATC = AFC/TDF or AFC = ATC x TDF TDF = Transfer Distribution Factor AFC = TFC – TRM – CBM - FBL – Impacts of Existing Commitments Confirmed, Accepted and Study reservations

  12. AFC Terms AFC = TFC – TRM – CBM - FBL – Impacts of Existing Commitments TFC = Total Flowgate Capacity TRM = Transmission Reliability Margin CBM = Capacity Benefit Margin FBL = Flowgate Base Loading Impacts of existing commitments • Firm – reservations & counterflows (depending upon horizon) • Non-firm – tags, reservations, & counterflows (depending upon horizon)

  13. TDF Value (Response factor) • TDF Value (Response factor) of a transaction is the impact of the transaction on a flow gate • For example transaction KCPL – ERCOTE will impact flow gate NESONENSTUL with 14% of its flows. • That means a 100 MW transaction KCPL – ERCOTE will have a 100 MW * 0.14 = 14 MW impact on flow gate. (reduces AFC with 14)

  14. PRE CONTINGENCY SITUATION CONSTRAINT Monitored Element Bart. SE Nort Barth. Rating 210 Flow 50 N.E.S. Delaware Contingency Element Flow 900 CONTINGENCY Flow gate direction

  15. POST CONTINGENCY SITUATION Bart. SE Nrth Bart 50 + 0.18 * 900 Rating 210 Flow 212 N.E.S. Delaware contingency Flow 0 Flow gate direction

  16. EXAMPLE OF A FLOW GATE • NAME: BVSNBVNESDEL • Rating: 210 Winter, 210 Fall, 210 Summer • Monitored element: • Bartlesville SE (CSWS)– N.Bartlesville (CSWS) 138 kV • Contingency element: • Northeastern (CSWS) – Delaware (CSWS) 345 kV

  17. Flowgate Types • TDF is a general term at SPP meaning either PTDF or OTDF • PTDF = Power Transfer Distribution Factor “The percentage of power transfer flowing through a facility or set of facilities (flowgate) for a particular transfer when there are no contingencies” • OTDF = Outage Transfer Distribution Factor “The percentage of a power transfer that flows through the monitored facility for a particular transfer when the contingency facility is switched out of service.”

  18. OTDF Flowgate Monitored element: Lone Oak to Sardis 138kV Contingency element: Pittsburg to Valiant 345kV

  19. PTDF Flowgate Monitored Element: Valiant - Lydia 345kV

  20. Power Transfer Distribution Factor Monitored Element PTDF = Transaction Flow on ME / Total Transaction Flow B Sink A Source Transaction Flow = 200 MW PTDF = 25% MW Transaction Flow on Monitored Element = 50 MW

  21. OTDF Flowgates OTDF = PTDFm + (LODFm,c xPTDFc) • LODF is the percentage of all flow on a contingency element that shifts to a monitored element with the loss of the contingent element • LODF includes all flows on a facility, not just transaction flows

  22. Line Outage Distribution Factor Monitored Element B Sink LODF = CE Flow Transferred / CE Total Flow A Source Contingency Element Monitored Element Flow pre-contingency = 200 MW Contingency Element Flow = 100 MW LODF for Contingency Element = 25% Transferred Flow = CE Total Flow x LODF 100 MW x 25% = 25 MW Ttransferred Post-contingency flow on Monitored Element = 225 MW

  23. Outage Transfer Distribution Factor OTDF = PTDFm + (LODFm,c xPTDFc) OTDF = PTDFm : the impact of a transaction on the monitored element of a flowgate as it sits with no contingency) + (LODFm,c:the percentage of flows on the contingency element that will transfer to the monitored element for the loss of the contingency element xPTDFc : the percent of transactions on the contingency element). In other words, the transaction amount on the contingency element transferred to the monitored element is a percent (LODF) of a percent (PTDF).

  24. OTDF Flowgate Parallel paths B Sink Transferred Flow = CE Flow X LODF A Source ME: PTDFm = 3% CE: PTDFc = 7% When the CE trips, 40% of its flow transfers to the ME (LODF). This is the same as saying 2.8% (7% x 40%) of the original transaction has moved over to the ME. Add this 2.8% to the original pre-contingency PTDFm of 3% to get a total of 5.8% (OTDF).

  25. Total Flowgate Capacity (TFC) • OTDF Flowgates, TFC is: “Total amount of power that can flow during the contingency without violating the emergency rating of the monitored facility.” • PTDF Flowgates, TFC is: “The total amount of power that can flow over a defined element set under pre-contingency conditions without violating a facility limit.” • Types of limits • Thermal • Voltage • Stability • Contractual

  26. Transmission Reliability Margin (TRM) at SPP “That amount of reserved flowgate capacity necessary to ensure that the interconnected transmission network is secure under a reasonable range of uncertainties in system conditions.” • Load Forecast – based on TPs forecasted hourly load • Variations in generation dispatch – based on real-time snapshots of network system conditions • Unaccounted for parallel flows – unidentified parties to multiple wheeling transactions • Operating Reserves – SPP Reserve Sharing Group reserve requirements

  27. Capacity Benefit Margin (CBM) “The amount of flowgate capacity reserved by load serving entities to ensure access to generation from interconnected systems to meet generation reliability requirements.” Steam-based CBM = 12% Hydro-based CBM = 9% For calculating AFC = 0

  28. Flowgate Base Loading (FBL) • Base Loading, Firm and Non-Firm (FBL & NFBL) = FLOWS • Calculated by RTRFCALC every hour using Net Interchange assuming all confirmed reservations are scheduled. • For Operating and Planning Horizons: Firm – Firm Counter-flows + Non-Firm – Non-Firm Counter-flows

  29. Available Flowgate Capacity Oasis Automation (ATC calculator) Hourly impacts on flowgate. RTRFCALC BASE FLOW AVAILABLE ATC FIRM / NON-FIRM

  30. Horizons • Study Horizon - Months 2 through 16 (Firm Monthly requests) • Planning Horizon - Day 2 through 31 (Firm Weekly and Daily requests) • Operating Horizon - Today and tomorrow if current time is after 1200 (Non-Firm Only Hourly requests)

  31. Available Flowgate Capacity Horizons Operating, Planning and Study Time Horizons Time of last Resynch

  32. Non-Firm AFC Operating Horizon

  33. Non-Firm AFC Operating Horizon NFAFC = TFC – TRM – FBL – NFCom, - New Res.

  34. New Non-Firm Committments in Operating Horizon • In Operating Horizon only non-firm reservations which are not yet scheduled should be decreasing available Non-Firm ATC. Those already scheduled are considered in Base Flows. • Current design of Oasis and Oasis Automation can’t identify reservations which are not scheduled yet. • That’s why all Non-Firm reservations in Study, Accepted and Confirmed are used to calculate total Non-Firm Commitments in Operating Horizon.

  35. Firm Planning Horizon FAFC = TFC – TRM – FBL – Com. - New Res.

  36. Firm Planning Horizon • Base flow of flow gates is calculated by RTRFCALC/EMS using the Net Interchange based on all Accepted and Confirmed reservations. • ATC calculator backs out Non-Firm Reservations (Accepted, Confirmed) used in base-flow calculation (4) and (5) because Accepted, Confirmed Non-Firm Reservations can be sold as firm. • ATC calculator also assumes Accepted and Confirmed Firm Counterflow Reservations will not be scheduled. They are backed out by the OASIS Automation creating a “pseudo” schedule. A counter-flow factor is used, currently .50, updated every month.

  37. Firm Planning Horizon • Grand fathered reservations are added with a 0.5 multiplier when calculating the Net Interchange of Control Areas in Planning Horizon. • Grand fathered counter flow reservations are backed out also using a 0.5 multiplier for both Firm and Non-Firm grand fathered counter flow reservations.

  38. Non-Firm PlanningHorizon NFAFC = TFC – TRM – FBL – Com, - New Res.

  39. Non-Firm PlanningHorizon • ATC calculator assumes that Accepted and Confirmed Firm and Non-Firm counter-flow reservations will not be scheduled, and backs 50% of them out. • Grand fathered reservations are added with a 0.5 multiplier when calculating the Net Interchange of Control Areas in Planning Horizon. • Grand fathered counter flow reservations are backed out also using a 0.5 multiplier for both Firm and Non-Firm grand fathered counter flow reservations. • 100% Confirmed Firm Counter-flow reservations added to AFC

  40. Firm and Non-Firm Study Horizons • Base flow calculations by Engineering backs out impacts of certain reservations. • Results in study Horizon flows that do not include impact of reservations.

  41. Available Flowgate Capacity Oasis Automation (ATC calculator) Hourly impacts on flowgate. RTRFCALC BASE FLOW AVAILABLE ATC FIRM / NON-FIRM

  42. Recap of ATC Formulas • The NERC components for ATC • ATC = TTC – TRM – CBM – Existing • Transmission Commitments • The SPP Formula for AFC • AFC = ATC x TDF • The SPP components of AFC • AFC = TFC – TRM – CBM - FBL - impacts of Existing Commitments) 42

  43. AFC Summary AFC = TFC – TRM – CBM - FBL - Commitments • TFC – most limiting of 30 flowgates • TRM – primarily Operating Reserves • CBM – 0 • FBL • Firm Model DNR flows • Non-Firm – model flows + 50% of counterflows from firm reservations • Existing Commitments • Study Horizon – Reservations, Counterflows – 100% of firm, 50% of non-firm • Planning Horizon – Reservations, Counterflows - 50% of firm, 50% of non-firm • Operating horizon – Tags, Counterflows – all non-firm

  44. SPP ATC Summary • All AFCs calculated from most limiting value of 30 associated flowgates • AFC = ATC x TDF of path • TRM factoring • NFATC (planning) = NFAFC (planning) / TDF of path • NFAFC (operating) / TDF of path a b

  45. Effective ATC is True ATC AFC = ATC x TDF ATC AFC TDF

  46. OASIS Automation Non-Firm AFC for a Flowgate on this Path

  47. Effective Non-Firm ATC

  48. Sensitivity Factor (TDF) for a Flowgate Affecting This Path

  49. Path ATC from Flowgate AFC • AFC = ATC x TDF • Nonfirm AFC = Effective Nonfirm ATC for the flowgate x Sensitivity • 327 = 7604 x .043 (7631 displayed) • Nonfirm ATC is actually Nonfirm AFC • Efffective ATC is derived ATC (AFC/TDF)

  50. Path ATC to Flowgate AFC Only 4% of the total flow from Source to Sink flows across the flowgate. AFC = ATC x TDF = 40 MW Sink TDF for this path is .04 Source 1000 MW ATC

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