Voltage Support Service (VSS) for CREZ Region

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

2. Voltage Control Challenges 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. 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. VSS Results For TSPs • 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. Access SOTE and VSS Applications • Login to SOTE • Login into ERCOT Citrix using 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. CREZ Dashboard Display

7. CREZ Dashboard Display (Continued) • 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. Application runtimes • SE, CA and VSS timestamps show the last successful runtime for these applications • Helps in identifying upstream application issues during failures ERCOT Public

9. Activate violations to VSS - Basecase • 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 ERCOT Public

10. Activate violations to VSS – Contingency Analysis • 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 ERCOT Public

11. CREZ Overview Displays • Click “CREZ Region” button • Shows 5 regions that the CREZ stations have been divided into

12. CREZ Overview Displays (Continued) • Click on any of the regions – Example “WEST” • Shows the stations in the zone and the connectivity between the stations

13. CREZ Overview Displays (Continued) • 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. CREZ Capacitor / Reactor status – Example Capacitors • 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. VSS Results • Click on “VSS Results” button • Shows the violations activated to VSS by the ERCOT Operator • Shows the Control Actions suggested by VSS

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

17. Initial List of Stations Identified As CREZ Related