1. Voltage Support Service (VSS) for CREZ Region Advanced Network Applications ERCOT

2. 2 V OLTAGE C ONTROL C HALLENGES IN CREZ Maintain voltages within operational limits Weak grid in the panhandle with no large synchronous generators to provide stability Long, highly compensated 345KV transmission lines to load centers in the north Extreme variability of wind power outputs and transfers Coordination between different Transmission Service Providers and the ERCOT Control room Minimize continuous variation and switching of control equipment

3. 3 VOLTAGE SUPPORT SERVICES (VSS) VSS is a tool built into the Alstom EMS Application VSS application is designed to resolve voltage violations by solving an optimization problem Uses following controls –Shunt Capacitors/reactors –Generators –Transformers Solves for both base case and post-contingency conditions. Runs every five minutes along with State Estimator and Contingency Analysis VSS application will be used to manage voltage violations in CREZ

4. 4 VSS R ESULTS F OR TSP S VSS results will be made available to all the TSPs using the SOTE application TSPs will see the same displays available to ERCOT operators in the control room thus helping in communications between ERCOT and TSPs Dashboard and Overview displays provided to improve CREZ TSPs’ situational awareness and system overview Tabular displays to provide detailed information about the neighboring TSPs’ reactive device statuses and outputs, voltages and suggested control actions

5. 5 A CCESS SOTE AND VSS A PPLICATIONS Login to SOTE –Login into ERCOT Citrix using https://gateway.ercot.com/https://gateway.ercot.com/ –Click on the SOTEEMS icon to open the SOTE system Once the SOTE application is open, click on the “VSS” icon in the toolbar on top of the window.

6. 6 CREZ D ASHBOARD D ISPLAY

7. 7 CREZ D ASHBOARD D ISPLAY (C ONTINUED ) Graph – Shows the PU voltages for all buses in the CREZ stations –Hover mouse on the dots to display the Station name and Bus PU voltage Tabular display – Shows Owner, Station, Voltage PU, Voltage KV etc.. –Highlights voltages above and below the limits

8. 8 A PPLICATION RUNTIMES ERCOT PUBLICFEBRUARY 21, 2012 SE, CA and VSS timestamps show the last successful runtime for these applications Helps in identifying upstream application issues during failures

9. 9 A CTIVATE VIOLATIONS TO VSS - B ASECASE ERCOT PUBLICFEBRUARY 21, 2012 Click on the “Basecase Voltage Violations” button to view the violations activated to VSS for resolution ERCOT Operator has the option to activate / deactivate violations to the VSS application

10. 10 A CTIVATE VIOLATIONS TO VSS – C ONTINGENCY A NALYSIS ERCOT PUBLICFEBRUARY 21, 2012 Click on the “Contingency Voltage Violations” button to view the Contingency violations activated to VSS for resolution ERCOT Operator has the option to activate / deactivate violations to the VSS application

11. 11 CREZ O VERVIEW D ISPLAYS Click “CREZ Region” button –Shows 5 regions that the CREZ stations have been divided into

12. 12 CREZ O VERVIEW D ISPLAYS (C ONTINUED ) Click on any of the regions – Example “WEST” –Shows the stations in the zone and the connectivity between the stations

13. 13 CREZ O VERVIEW D ISPLAYS (C ONTINUED ) Click on any of the stations – Example “BITTER” –Shows the station online for the selected station –Same displays used by the ERCOT control room

14. 14 CREZ C APACITOR / R EACTOR STATUS – E XAMPLE C APACITORS Click on “Capacitors in service” button –Shows the CREZ region Capacitors that are switched in Click on “Capacitors Available” button –Shows the CREZ region Capacitors that are switched off but available to turn on

15. 15 VSS R ESULTS Click on “VSS Results” button –Shows the violations activated to VSS by the ERCOT Operator –Shows the Control Actions suggested by VSS

16. 16 VSS C ONTROLS Click on “VSS Controls” button –Shows all reactive devices that can provide voltage control in the CREZ region

17. 17 I NITIAL L IST OF S TATIONS I DENTIFIED A S CREZ R ELATED