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

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

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

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!

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

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)

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

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)

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

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

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 & & & & & & 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.

12Powertech Labs Inc. Questions?

13Powertech Labs Inc. Northwest Quadrant

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

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

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

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

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

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

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

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

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