AFC – New Developments

1. AFC – New Developments EMS USER GROUP Sep 12 2004 EMS USER GROUP SEP 12, 2004

2. WHAT IS AVAILABLE FLOWGATE CAPACITY • Available Flowgate Capacity or AFC is a flowbased • approach to determine the availability of transmission • capacity. This approach predicts and analyzes flows on • constrained facilities (called “flowgates”) when • determining whether sufficient capacity exists to • approve a transmission service request. • The AFC value for a particular flowgate is the amount • of transfer capability over that flowgate that remains • available for additional transmission service • reservations above and beyond existing uses of the • transmission system. EMS USER GROUP SEP 12, 2004

3. FLOWGATE A single or group of Transmission elements intended to model MW flow impact related to transmission limitation and transmission system usage. PTDF FLOWGATE: When the monitored elements are monitored without considering the impact of any contingency. OTDF FLOWGATE: When the monitored elements are monitored after considering the impact of one or more outages. EMS USER GROUP SEP 12, 2004

4. RESPONSE FACTORS Line Outage Distribution Factor (LODF): Defines the impact of contingent element/s on monitored element/s in terms of percentage of MW flow. Power Transfer Distribution Factor (PTDF): Defines the impact of a transfer on a flowgate, in terms of percentage of MW amount of transfer. PTDFfg = PTDFle + LODF * PTDFce EMS USER GROUP SEP 12, 2004

5. EMS USER GROUP SEP 12, 2004

6. AFC Horizons Operating Horizon: Includes all hours of current day and after 12:00 PM includes all hours of next day. Hourly values are calculated for this horizon. Planning Horizon: Extends from end of operating horizon to 31st Day. Hourly values are calculated for 1st seven days and daily values are calculated for the rest. Study Horizon: Extends from end of planning horizon to month 18. Monthly values are computed for this horizon. EMS USER GROUP SEP 12, 2004

7. AFC CALCULATIONS • Model Building • Outages • planned generation • Load Forecast • Confirmed Firm schedules • Accepted, Confirmed and Counteroffer reservations (firm and • non firm) • Power Flow Solution • Power flow is performed for all hourly and daily time points. The Output of power flow is: EMS USER GROUP SEP 12, 2004

8. AFC CALCULATIONS • Power flow Output: • Flowgate flows for all flowgates all time points • Sensitivities of top 15 flow gates for each transfer path EMS USER GROUP SEP 12, 2004

9. AFC CALCULATIONS • AFC Formulas: • Firm AFC = Rating – TRM –CBM – Base Flowfirm • Non Firm AFC = Rating – TRM –CBM – Base Flownon-firm • Base Flow : Base flow calculation for Firm AFC takes into account all existing firm use of transmission system including • Firm PTP • Service to Network and Native Load Customers • Other Firm Transmission service such as granfathered • agreements pre FERC order 888. EMS USER GROUP SEP 12, 2004

10. RESYNCHRONIZATION Operating horizon: every hour. Planning horizon: every six hours. Study Horizon: Every month During RFCALC resynchronization models are built for each hour and Power flow is performed. During Oasis Automation Resynchronization it retrieves all sensitivities and base flows from RFCALC. EMS USER GROUP SEP 12, 2004

11. IN BETWEEN RESYNCHRONIZATION Algebraic adjustments are done to AFCs, using sensitivity factors. Reevaluation and Reclamation: When an status change event occurs like a reservation changes from accepted to withdrawn all impacted reservations are reevaluated. AFC may be reclaimed on affected flowgates if necessary. . EMS USER GROUP SEP 12, 2004

12. SINGLE SOURCE CONCEPT • Response Factors measure the impact (i.e., the incremental • loading) that each source-to-sink transaction has on a monitored • flowgate. • Response Factors are transaction-specific in the sense that each • source-to-sink pair will have a set of Response Factors based on • the power flows associated with that source-to-sink pair. • Response Factors are flowgate-specific in the sense that every • source-to-sink transaction will have a distinct Response Factor • for each monitored flowgate. • Entergy calculates Response Factors for each generator that is • directly interconnected with the Entergy transmission system, • including all generators within the Entergy control area, • regardless of ownership or affiliation • . EMS USER GROUP SEP 12, 2004

13. GENERATOR and INTERFACE LIMITS • Regardless of the applicable AFC values, accepted transmission • service requests from a particular generator shall not exceed the • maximum output of that generator. • The amount of transmission service available across a control • area interface can not exceed the total interface rating between • the two control areas. Consistent with NERC Operating Policies • and operating agreements, the capacity between these interfaces • is rated. This limit is typically defined by the thermal limit of all • transmission facilities that define the interface. • Pmax and Interface limits are honored by proxy flowgates. • . EMS USER GROUP SEP 12, 2004

14. COUNTERFLOWS • Power flow solution includes 100% counterflows. • To account for uncertainty that the counterflow transactions will • be actually scheduled we remove a percentage of counterflow • from base flow. • . • . EMS USER GROUP SEP 12, 2004

15. NON FIRM PTP X Impact X NON FIRM PTP X’ Impact X’ Counterflow NON FIRM Network Y Impact Y NON FIRM Network Y’ Y’ImpactY’ Flowgate 1 • COUNTERFLOWS • . EMS USER GROUP SEP 12, 2004

16. COUNTERFLOW CALCULATION • Within RFCALC, for each Flowgate determine the transfer paths • with negative sensitivity above a threshold. • Of this list determine the paths which have a reservation which • was modeled in base case. • Determine the counterflow adjustment by using sensitivities and • counterflow factors. • Firm Service : Include 50% CF • Non Firm Service: Include 70% CF. • . • . EMS USER GROUP SEP 12, 2004

17. ? • QUESTIONS • . EMS USER GROUP SEP 12, 2004