AES Buffalo Gap Wind FarmBuffalo Gap 2 - 232.5 MW

155 – GE 1.5 sle

Presented August 22, 2008

By

Robert Sims

AES Wind Generation

AES Buffalo GapWind Farm

Three Phases totaling 524.3 MW Summary:

Located in Taylor and Nolan Counties SW of Abilene.Buffalo Gap 1 – 67 Vestas V-80, 1.8 MW turbines totaling 120.6 MW, COD late/05Buffalo Gap 2 – 155 GE 1.5 sle, 1.5 MW turbines totaling 232.5 MW, COD early/07Buffalo Gap 3 – 74 Siemens 2.3 MW turbines totaling 170.2 MW, COD mid/08.Interconnected to AEP Bluff Creek at 138 kV via project owned 12 mile 138 kV T/L.

AES Buffalo Gap 2 GE 1.5 sle Wind Turbine Physical characteristics & Rating

Three blades, rotor diameter of 77 M (253 ft.), swept area 4657 sq meters (50,128 sg. ft.)80 meter tubular steel tower (262.5 ft.)Variable speed operation, main rotor =10-20 rpmPower regulation via adjustable blade pitch (electric) & electronic generator torque control Main gearbox ratio 1:78 for variable generator speed of 870 to 1600 rpm with nominal power at 1440 rpm. Rated 1.5 MW and 575 volts 3 phaseOver 5000 installed worldwide

GE 1.5 MW sle Turbine

GE 1.5 sle Turbine

GE 1.5 sle TurbineMethod of startingWhen the wind in the area increases above the cut in speed (3.5 m/s) the turbine blades are pitched from “feather” to “power” and the wind begins to turn and accelerate the rotor. Once the rotor achieves operational speed of 10-11 rpm the turbine is softly connected to the line with a ramp up of the power electronics.

Method of controlling power outputOutput power is regulated through a combination of variable blade pitch for control of rotor torque, and variable frequency control of the generator to control drive train speed and torque. During a wind gust the rotor frequency is increased and the drive train is allowed to accelerate while reduging torque to “store” the gust power spike as kinetic energy in the rotor like a flywheel. Once the gust passes the controller extracts the power in the rotor and slows it back to the nominal speed.

Method of stoppingFor normal shutdown the rotor blades are pitched to feather. For an emergency shutdown the blades are pitched to feather (battery back-up if required) and a disk brake is engaged on the high speed shaft.

GE 1.5 sle Turbine

Reactive Devices as Part of the TurbineThe GE 1.5SLE 60Hz wind turbine uses a power converter system that consists of an electronic converter connected to the generator rotor, a DC intermediate circuit, and a power inverter on the grid side. This system functions as a pulse-width-modulated variable frequency converter in 4-quadrant operation.

The converter its self consists of an insulated gate bipolar transistor (IGBT) power module and the associated electrical equipment. Variable output frequency of the converter allows a rotational speed-module operation of the generator within the range of 870 rpm to 1600 rpm.

The Standard GE 1.5SLE 60Hz Wind Turbine is designed with a selectable power factor. At 1.0 pu voltage (575 V) and full power (1500 kW), a power factor of 0.95 overexcited (reactive power delivered by the wind turbine) to 0.90 underexcited (reactive power absorbed by the wind turbine) as measured at the terminals of the trubine. The power factor is settable at each WTG or controlled remotely and dynamically by the wind farm SCADA system (more on this later).

Optional Reactive Capability: 0.90 overexcited / 0.90 under-excited at 1.0 pu voltage (575 V) and full power (1500 kW) is available at an additional cost.

GE 1.5 MW sle Turbine

GE 1.5 sle TurbineGrid Frequency Tolerance

Continuous operation in the frequency range of 57.5-61.5 Hz. Trips as the frequency drops below 56.5 Hz or exceeds 62.5 Hz.

GE 1.5 sle TurbineVoltage Tolerance (At the 575 volt terminals of the turbine!)

Voltage limits for the GE 1.5 MW, 60 Hz wind turbine are as follows:

AES Buffalo Gap 2 Site Selection Criteria

The Buffalo Gap project location was selected based on it’s high elevation resulting in high average wind speeds, rural location with compatible land use, and proximity to transmission lines.

Cabling Connections to collector substation & Electrical characteristicsThe GE turbines have a Padmounted type transformer located at the base of each turbine to raise the voltage from the 575 volt turbine terminal voltage to 34.5 kV for the site power collection system. A combination of underground and overhead power lines based on standard utility practices carry the power to the central step up substation. Typically 20-30 MW of generation is connected to each substation 34.5 kV breaker positions.

Operational IssuesThe only operational issues of moderate significance has been disturbances resulting from lightning strikes to overhead portions of the system.

AES BG 2 34.5 kV System

Fdr#1-2

Fdr#1-1

4542 Ruffner St.

San Diego, CA 92111

Robert L. Sims

AES Wind Generation, Inc.Buffalo Gap 1, 2, 3

Simplified 1-line diagramSIZE FSCM NO DWG NO REV

B 2SCALE n/a 7/27/08 SHEET 1 OF 1

Fdr#1-3

Fdr#1-4

Project T/L 138 kV, 12 miles, 2 x 954 MCM ACSR

(COD 4th qtr. /05)

138 kVBkr

Substation Control & Relaying

(per AEP Reqmts)

Xfmr #184/112/140 MVA

138-34.5 kVWye-Delta-Wye

8.5 %(w/HS LTC)

KWhEPS138 kV

Bkr

Fdr#2-2

Fdr#2-3

Fdr#2-4

Substation Control

& Relaying

Xfmr #C-175/100/125 MVA

138-34.5 kVWye-Delta-Wye

9.5 %

Cirello Substation(COD 1st qtr ‘07)

Buffalo Gap Substation(COD 4th qtr. ’05)

TSP / EPS revenue meteringw / loss adjustment

2 mi, 2 x 556 AA

Point of AEP/ERCOT

Interconnection

AEP Bluff Creek Sub(COD 3rd qtr. ’06)

KWhBG-1

KWhBG-2

Fiber Optic Comm. LinkBetween Substations

on 138 kV T/L

Fdr#2-1

AEP DFR & RTU

QSE RTUDTT –

Bluff Ck.

Buffalo Gap 1 - 120 MW COD 4th qtr. ‘05

67 x Vestas V-80 1.8 MW Turbines

138 kVBkr

138 kVBkr

AEP T/L 138 kV, 2 miles, 2 x 795 MCM ACSS

(COD 4th qtr. ’06)

Project T/L 138 kV, 8 miles total

Fdr#2-5

AEP DFR & RTU

QSE RTU

Fdr#2-6

Fdr#2-7

6 mi, 2 x 954 ACSR

Fdr#3-2

Fdr#3-1

Fdr#3-3

Fdr#3-4

138 kV Bkr

Xfmr #2111/148/185 MVA

138-34.5 kVWye-Delta-Wye

9.5 %

KWhBG-3

Note 1

Note 1Note 1

Note 1

FUSE

PF Caps6 x 10.8 MVAr

64.8 MVAr total

BG-3 Additions(COD 2nd qtr. ’08)

Buffalo Gap 2 - 232.5 MW COD 1st qtr ‘07

155 x General Electric 1.5 MW sle Turbines

Fdr#2-8

PF Caps6 steps x 7.2 MVAr

43.2 MVAr total

FUSE

Note 2

TRIP

TRIP

TRIP

TRIP

Xfmr #C-275/100/125 MVA

138-34.5 kVWye-Delta-Wye

9.5 %

TRIP

Circuit Switcher

Circuit Switcher

CVT x 3

FUSE

Note 1) Total KWh to QSE for Generation Splitting Calculation

Note 2) CT’s & PT’s used for AEP relaying and line protection, trips all 3 breakers for line fault.Buffalo Gap 3 – 170.2 MW

COD 3rd qtr ‘0874 x Siemens 2.3 MW Turbines

PF Caps6 steps x 7.2 MVAr

43.2 MVAr total

AES BG 2 Control System

Location of Control Rooms / FacilitiesThe project has both local supervision & control, along with remote

supervision & control 24/7 from the AES Wind Generation central control facility in Palm Springs, California.

SCADAThe project has separate turbine SCADA systems for the 3 types of

turbines associated with the 3 phases of the project (Vestas, GE, & Siemens) along with a separate SCADA system for the interconnection substations.

Turbine Power ControlTurbine power is generally controlled locally by each turbine

individually to maximize energy capture. However, the local control can be overridden for the fleet by the turbine SCADA control and capped at lower max power levels.

AES BG 2 Control System Reactive ControlIndividual turbine reactive power is controlled centrally from the GE

SCADA system. Voltage and power factor are monitored at the main collector substation. The system can operate on a voltage set point, or a power factor set point, and remotely adjusts the power electronic converters in each of the turbines along with automatically switching the 34.5 kV substation capacitor banks.

Switch / Breaker ControlSubstation control can be local from the substation using either

traditional control devices on the switchboard or a SCADA terminal in the substation control house, or remote supervision and control via the substation SCADA.

Special Protection Schemes (SPS)The Buffalo Gap 3 project is being fitted with a short term SPS to

reduce generation in the event of the loss of one of the 345 kV lines to Bluff Creek during maximum wind power generation. This SPS will be required for a few years until area transmission improvements are completed.

Thank You

robert.sims@aes.com