CSC Limit Calculation & Posting

1. CSC Limit Calculation & Posting John Adams jadams@ercot.com Operations Support 5/11/2004

2. Course Roadmap • Review of How ERCOT performs Daily CSC Limit Calculations • Identification of Posting Location • Note – Variation in these processes by the professional performing the calculation is allowed for special circumstances

3. Farmersville – Royse Switch North • Farmersville – Royse Switch South Houston • Graham-Parker • Graham-Benbrook North Northeast • Jewett – T.H. Wharton • Gibbons Creek – Obrien • Jewett – Tomball • Roans Prairie - Kuykendahl CRE • Sandow-Temple 1 • Sandow-Temple 2 West • STP Dow 18 • STP Dow 27 • STP WAP 39 CRE South CSC Monitoring • CSC Limits are defined through detailed planning and engineering studies

4. Create a Power Flow Base Case • Continuously during the week TDSP’s provide updates to the ERCOT network model. • Once/week: Typically Tuesday, a database load is performed • Once/Week: Normally the following day, a new study base case is created.

5. Create a Daily Base Case • Operations Engineer uses the power flow base case, and overlays the load forecast, the generation plan, and the outages scheduled for peak hour (typically) • Operations engineer reads the outage notes, looking for outages with significant impact on CSC’s. • Solve Power flow case, execute contingency analysis. Save case as daily base case.

6. Calculate South-North limit • Examine post-contingency overloads to see if violations on CSC, CRE or associated elements already exist. • If not, increase load in North Central load Zone [wxznrthc]. Decrease load in South Central load zone and Southern Zone. • Run Contingency analysis and examine results for post-contingency overloading on CSC’s and associated elements until post contingency overload detected.

7. Calculate South-North limit • When post-contingency overload detected, open contingency line in base case and scale load in North Central/South & South Central until post-contingency overload 100% of emergency rating.{15 minute rating may be used if an RAP exists for this element} • Observe the flow on Sandow-Temple double circuit and record as the S-N limit.

8. Calculate South-North limit • Examine Outage notes to determine if an outage is affecting the limit during the day. If so; repeat limit calculation process for period after restoration of the outage.

9. Calculate North-Houston limit • Retrieve daily save case. • Examine post-contingency overloads to see if violations on CSC, CRE or associated elements already exist for North-Houston • If not, increase load in Coast load Zone [wxzcoast]. Decrease load in East load zone and North Central Zone. • Run Contingency analysis and examine results for post-contingency overloading on CSC’s and associated elements [or under voltage] until post contingency overload detected.

10. Calculate North-Houston limit • When a post-contingency overload is detected, open the contingency line in the power flow case and scale load in until post-contingency overload is 100% of emergency rating.{15 minute rating may be used if an RAP exists for this element} • Observe the flow on Gibbons Creek-O'Brien + Jewet-THW + Jewet-Tomball + Roans Prairie-Kuykendahl-King and record as the N-H limit.

11. Calculate North-Houston limit • Examine Outage notes to determine if an outage is affecting the limit during the day. If so; repeat limit calculation process for period after restoration of the outage.

12. Calculate South-Houston limit • Similar to North-Houston & South –North; but scale up load in Coast load zone, and down in South load zone. • Sum STP-DOW double circuit + STP-WAP for limit.

13. Calculate Northeast-North limit • Examine post-contingency overloads to see if violations on CSC, CRE or associated elements already exist. • If not, increase generation at NORTHEAST zone generation stations • Run Contingency analysis and examine results for post-contingency overloading on CSC’s and associated elements until post contingency overload detected.

14. Calculate Northeast-North limit • When post-contingency overload detected, open contingency line in base case and scale generation in Northeast until post-contingency overload is 100% of emergency rating.{15 minute rating may be used if an RAP exists for this element} • Observe the flow on Farmersville-Royce double circuit and record as the NE-N limit.

15. Calculate West-North limit • Similar to Northeast-North CSC calculation but Sum Graham-Parker and Graham-Benbrook for the CSC limit.

16. Posting of CSC limits • https://tcr.ercot.com/default.cfm?func=tcrpostings