2. Northwest Quadrant Joint Security Study Southern Company Headquarters Birmingham, Alabama August 12, 2002 Presented by Saeed Arabi

3. 2Powertech Labs Inc. Outline  Scope  Assumptions  Results  Proposed Solutions

4. 3Powertech Labs Inc. Joint Security Study Scope  Identify critical contingencies and constraints Scanning about two-thirds of the State of Alabama, the extreme northwest portion of Georgia, and a small portion of eastern MississippiScanning about two-thirds of the State of Alabama, the extreme northwest portion of Georgia, and a small portion of eastern Mississippi  Determine generation limits for various system conditions  Define the boundary of the security problem SensitivitiesSensitivities Worst-case scenarioWorst-case scenario  Propose solutions to stability constraints

5. 4Powertech Labs Inc. Joint Security Study Assumptions  2003 peak and 50% of expected peak (off-peak) load level cases used Off-peak case based upon economic dispatchOff-peak case based upon economic dispatch PSS assumed to be available on all new unitsPSS assumed to be available on all new units  New units were added to the NWQ according to a joint queue developed by the 3 companies Firm Transmission Service confirmedFirm Transmission Service confirmed Firm Transmission Service requestedFirm Transmission Service requested Interconnection confirmedInterconnection confirmed Interconnection requestedInterconnection requested  To validate stability results, “hypothetical” thermal upgrades were added to relieve thermal constraints. Not a thermal study!Not a thermal study!

6. 5Powertech Labs Inc. Joint Security Study Assumptions (cont)  Four “Normal” source/sink scenarios EST-EST: Sink generation in the company territory where it is locatedEST-EST: Sink generation in the company territory where it is located EST-E: Sink generation in EntergyEST-E: Sink generation in Entergy EST-S: Sink generation in SouthernEST-S: Sink generation in Southern EST-T: Sink generation in TVAEST-T: Sink generation in TVA  One “Worst” source/sink scenario EST_W-S: Source ordered by TDFEST_W-S: Source ordered by TDF  Do not violate interface capacities of 3 companies

7. 6Powertech Labs Inc.  Standard criteria used Used each company’s current and voltage ratings and limitsUsed each company’s current and voltage ratings and limits Voltage collapse margin: 5%Voltage collapse margin: 5% Transient voltage dips: 75% for < 40 cyclesTransient voltage dips: 75% for < 40 cycles Minimum damping: 3%Minimum damping: 3% Fault clearing margin: 2 cyclesFault clearing margin: 2 cycles  Combinations of constant power, current, and impedance load models used Joint Security Study Assumptions (cont)

8. 7Powertech Labs Inc.  The most limiting contingency from a damping standpoint was the Miller - Bellefonte 500 kV line (Line tripping event)  The most limiting contingency from a transient voltage dip standpoint was the Farley – Raccoon Creek 500 kV line (Normally cleared 3ph fault)  The most limiting normal scenario identified was EST-S (Sinking to Southern under off-peak conditions)  SVC will raise stability limit some – Big increases will require 500 kV lines Joint Security Study Results

9. 8Powertech Labs Inc.  New generation added without PSS severely deteriorated system damping: PSS required  Limit is very source/sink dependent: Sequential studies required  5625 MW “Normal” limit based on the joint EST Queue  3500 MW “Worst” limit based on TDF of Farley-Raccoon Line (Limits are above year 2000 generation)  Line re-conductoring had small impact on security limits Table 3-2 w/ PSS w/o PSS EST-S>95000 Joint Security Study Results (cont)

10. 9Powertech Labs Inc. Joint Security Study Results (cont)

11. 10Powertech Labs Inc. Joint Security Study- Proposed Solutions  Dynamic shunt compensation can increase the transient security limit by 1400 – 2150 MW (In South Bainbridge and Auburn regions) Minimal increase after 900 Mvar addedMinimal increase after 900 Mvar added 230 kV re-conductoring and static capacitors would be required230 kV re-conductoring and static capacitors would be required Cost of SVC: Approximately $5 million per 100 MvarCost of SVC: Approximately $5 million per 100 Mvar  Series compensation was evaluated, but found to not be an effective solution Candidate lines were already heavily loadedCandidate lines were already heavily loaded

12. 11Powertech Labs Inc. 8,8688,8688,8208,6928,6787,728 Voltage Stability (with 5% Margin) 7,6007,6007,6007,2507,2507,150 Thermal * (at 120% Loading) 7,7747,5897,2096,8406,6705,625 Transient Security (Voltage Dip) 8,3508,3507,7007,0007,0004,300 Voltage Magnitude (0.9 pu) 200 & 900 300 & 700 400 & 500 200 & 300 300 & 100 0 & 0 Shunt Compensation by MSC & TSC (MVAr) Limit Type Table 4 ‑ 2: Shunt Compensation and EST–S Scenario Limits (MW) – Various Phenomena for Contingency 15 (Critical Path Highlighted). Critical Path Limits With Shunt Compensation * Not representative of thermal studies for specific transfers.

13. 12Powertech Labs Inc. Questions?

14. 13Powertech Labs Inc. Northwest Quadrant

15. 14Powertech Labs Inc. Background  Southern company internal studies indicated ~5000 MW of new generation above year 2000 before transient stability limit reached  ~20,000 MW of new generation requests in the NWQ  Joint study initiated with Powertech Labs last summer  Entergy and TVA included in the study and model  TSR facility studies on hold pending the results of the joint study

16. 15Powertech Labs Inc. Limit Based on Transient Voltage Dip Criteria (Off-peak Case)

17. 16Powertech Labs Inc. Limit Based on Voltage Stability Criteria (Peak Case)

18. 17Powertech Labs Inc. Pre-contingency Loading on Farley- Raccoon Line (At Limit for Transient Voltage Dip – Off-peak)

19. 18Powertech Labs Inc. Transmission Distribution Factors (TDF) for Farley-Raccoon Line

20. 19Powertech Labs Inc. Limit Based on Transient Voltage Dip Criteria (Off-peak Case)

21. 20Powertech Labs Inc. Limit Based on Voltage Stability Criteria (Peak Case)

22. 21Powertech Labs Inc. Pre-contingency Loading on Farley- Raccoon Line (At Limit for Transient Voltage Dip – Off-peak)

23. 22Powertech Labs Inc. Limit Based on Most Constraining Criteria (Worst-case Scenario)