WGR Equivalent Modeling Keith Smith Network Model Engineer RARF Workshop III August 29, 2013

2 System Protection Model Equivalent –Aggregated turbines modeled at.69 kV –Turbine step-up transformers aggregated into one kV transformer –Collector system represented as single line –Provides more accurate fault data than aggregate turbine modeled at 34.5 kV level –Grounded Wye-Delta connection very common for turbine step-up transformers, limits single line to ground fault current contributions from turbine WGR Equivalent Model

3 Calculating impedances for equivalent model –Equivalent turbine impedance calculated as N turbines in parallel –Equivalent transformer impedance calculated as N transformers in parallel –Equivalent collector system impedance calculated from collector system cable data using the following equation: –Where n = number of turbines feeding cable segment N = number of total turbines Equivalent Methodology

4 3-Phase to Ground Fault Full System

5 3-Phase to Ground Fault Equivalent

6 Single Line to Ground Fault Full System

7 Single Line to Ground Fault Equivalent

8 Collector System Example

9 Collector System RARF Format GENERATOR DETAILSCable TypeWIND SEGMENT DETAILS Resource Name (Unit Code/Mnemonic)Cable TypeFromToCircuit Number Voltage Level Cable Segment Length Number of Turbines On Cable Segment List alpha/numeric kVin kftInteger WIND_FARM1000 kcmil WIND_FARM1/0 AWG WIND_FARM1000 kcmil WIND_FARM1/0 AWG WIND_FARM1/0 AWG WIND_FARM500 kcmil WIND_FARM500 kcmil WIND_FARM4/0 AWG WIND_FARM1/0 AWG WIND_FARM1/0 AWG WIND_FARM1/0 AWG WIND_FARM1000 kcmil GENERATOR DETAILS COLLECTION SYSTEM DETAILED MODELPOSITIVE SEQUENCE DATAZERO SEQUENCE DATA Resource Name (Unit Code/Mnemonic)Cable Type Voltage Level kVR/kftX/kftCharging Bc/kftR0/kftX0/kft List kV(p.u. on 100 MVA base) WIND_FARM1000 kcmil E WIND_FARM500 kcmil E WIND_FARM4/0 AWG E WIND_FARM1/0 AWG E

10 Generator Data Required turbine data for system protection cases

11 Current Limits Required for type 3 and type 4 turbines

12 QUESTIONS?