RMR Exit for Spencer 5 – Remedial Action Plans Chris Ngai Jay Teixeira Regional Planning Group April 16, 2010

Summary ERCOT staff analysis of the Spencer 5 exit from RMR status indicated that the Remedial Action Plans (RAPs) described herein would facilitate the unit’s RMR exit. Slide 3 contains a list of the six RAPs proposed as an RMR exit strategy for Spencer 5 with detailed descriptions of the RAPs in the subsequent slides. Review of the RAPs submitted by Oncor on April 14 is currently in progress. RAPs were revised to take into account current construction activity. This analysis was performed using the 2010 summer peak case; last updated on December 11, 2009.

List of RAPs RAP Description Contingency/Overload pair Est. Hours/yr* 1 Carrollton RAP L: Lewisville Switch (645)-Highland E 138kV(1970) line C: Lewisville Switch (645)-Highland(664) 613 C: Highland (664) - Canyon (668) 7 2 Lake Pointe RAP L: Carrollton Northwest-LakePointe 138kV line C: Lewisville Switch 345/138kV autotransformer 208** 3 Highland RAP L: Lewisville Switch (645)-Highland E 138kV(1970) 138kV line C: Coppell-Lewisville Switch 10 4 Frisco RAP L: Collins (2370) to Frisco (681) 138kV line C: Denton Steam – Corinth; Teasley to Pockrus 278 5 Frisco Voltage RAP L: Low voltage at Frisco and Panther Creek C: Collin to Frisco 138kV line 90 6 Arco RAP After Operation of Carrollton RAP or Lake Pointe RAP See above *based on SSWG load level and one unit unavailable **138 kV line from NW Carrollton to Lewisville still in service through summer this RAP not needed

RAP 1 – Carrollton RAP Problem 1 Contingent element: Lewisville Switch (645)-Highland(664) Overload element: Lewisville Switch (645)-Highland E 138kV(1970) line (Rate A/B/C: 214/214/214) RAP operation: Open NW Carrollton (2361) – Lewisville Switch (646) 345kV and 138 kV lines Level of overload: 117.8% Rate B (252.1MVA) Estimated number of hours RAP would operate in year 2010: 613 hours

RAP 1 – Carrollton RAP cont’d 613 hours Contingency: Lewisville Switch (645) to Highland E (1970) 138kV line Overload element: Lewisville Switch (645) to Highland (664) 138kV line RAP action: Open the NW Carrollton (2361) – Lewisville Switch (646) 345kV line Denton NW Carrollton Roanoke

RAP 1 – Carrollton RAP cont’d Problem 2 Contingent element: Highland (664) - Canyon (668) Oveload element: Lewisville Switch (645)-Highland E 138kV(1970) line (Rate A/B/C: 214/214/214) RAP operation: Open the NW Carrollton (2361) – Lewisville Switch (646) 345kV and 138 kV lines Level of overload: 101.9% Rate B (218.1MVA) Estimated number of hours RAP would operate in year 2010: 7 hours

RAP 1 – Carrollton RAP cont’d 7 hours Contingency: Highland (664) to Canyon (668) 138kV line Overload element: Lewisville Switch (645) to Highland E (1970) 138kV line RAP action: Open the NW Carrollton (2361) – Lewisville Switch (646) 345kV line NW Carrollton Roanoke Denton

Contingent element: Lewisville Switch (645)-Highland(664) RAP 2 – Lake Pointe RAP Contingent element: Lewisville Switch (645)-Highland(664) Overload element: Lewisville Switch 345/138kV autotransformer (Rate A/B/C: 700/700/700) RAP operation: Open the line TNMP Lake Pointe (37010) – TNMP Lewisville (37080) Level of overload: 113.3% Rate B (317.3MVA) Estimated number of hours RAP would operate in year 2010: 208 hours Not needed in 2010 summer due to 138 kV line from Lewisville to NW Carrollton line being in case May activate Arco RAP to handle Double Circuit contingency Causes Collin to Frisco to overload

RAP 2 – Lake Pointe RAP cont’d 208 hours Contingency: Lewisville Switch 345/138kV autotransformer Overload element: Carrollton Northwest – Lake Pointe 138kV line RAP action: Open the line TNMP Lake Pointe (37010) – TNMP Lewisville (37080) Denton NW Carrollton

Contingent element: Coppell-Lewisville Switch RAP 3 - Highland RAP Contingent element: Coppell-Lewisville Switch Overload element: Lewisville Switch (645)-Highland E 138kV(1970) 138kV line (Rate A/B/C: 214/214/214) RAP operation: Open Lewisville Highlands (37050) – Lewisville West (37060) Level of overload: 101.8% Rate B (217.8MVA) Estimated number of hours RAP would operate in year 2010: 10 hours Coppell to Lewisville Switch contingency sectionalized to Lewisville Switch to Lewisville. Overload element: Coppell Tap to McKamy Tap May not related to Spencer RMR

RAP 3 - Highland RAP cont’d 10 hours Denton Contingency: Coppell to Lewisville Switch 138kV line Overload element: Lewisville Switch (645) - Highland E (1970) 138kV line RAP action: Open Lewisville Highlands (37050) – Lewisville West (37060) NW Carrollton

Contingent element: Denton Steam – Corinth & Teasley - Pockrus RAP 4 – Frisco RAP Contingent element: Denton Steam – Corinth & Teasley - Pockrus Overload element: Collins (2370) to Frisco (681) 138kV line (Rate A/B/C: 256/256/256) RAP operation: Raise the voltage of the West Denton 138kV side to 140kV Modify the Collin Switch Reactor SPS so that it will operate when the Collin to Frisco line overloads. If this does not resolve the overload, put all three capacitor banks at Navo in-service Verify Argyle and Corinth capacitors are on Level of overload: 109% Rate B (276.9MVA) Estimated number of hours RAP would operate in year 2010: 278 hours

RAP 4 – Frisco RAP cont’d 278 hours Collin North Denton Spencer Contingency: Denton Steam auto-transformer to Corinth & Teasley to Pockrus 138kV line Overload element: Collins (2370) to Frisco (681) 138kV line RAP action: Raise the voltage of the West Denton 138kV side to 140kV Collin Switch Reactor SPS operates when the Collin to Frisco line overloads put all three capacitor banks at Navo in-service Collin North Denton Spencer

RAP 5 - Frisco Voltage RAP Contingent element: Collin to Frisco 138kV line Low voltage element: Frisco and Panther Creek bus RAP operation: Raise voltage at West Denton to 1.02~1.05 adjust power factor/load Level of overload: 0.8942 p.u. Estimated number of hours RAP would operate in year 2010: <0.92 p.u. – 584 hours (Brazos Criteria) <0.90 p.u. – 90 hours (ERCOT Criteria)

Carrollton RAP (line loadings refer to Collin to Frisco) RAP 6 – Arco RAP Cause Carrollton RAP Lake Pointe RAP Overload element: Collin (2370) to Frisco (681) 138kV line (Rate A/B/C: 256/256/256) RAP operation: Open Arco (1993) – Krugerville (1994)138kV line Level of overload: Carrollton RAP (line loadings refer to Collin to Frisco) Problem 1 - 115.4% (239.4 MVA) after Carrollton RAP [pre RAP: 104.1% 266.4 MVA Collins SPS would relieve this but not after Carrollton RAP so should use Arco RAP instead]] Problem 2 – 113.8% (291.4 MVA) after Carrollton RAP [pre RAP: 102.3% 262.0 MVA Collins SPS would relieve this but not after Carrollton RAP so should use Arco RAP instead]] Lake Pointe RAP - 111.2% (284.6 MVA) after Lake Pointe RAP [pre RAP: 110.6% 283 MVA]

RAP 6 – Arco RAP cont’d Krugerville Navo Panther Creek Arco Collin Same # of hours as Carrollton RAP & Highland RAP Overload element: Collins (2370) to Frisco (681) 138kV line Contingency: overload caused by Carrollton RAP and Lake Pointe RAP RAP action: Open Arco (1993) – Krugerville (1994)138kV line Collin Krugerville Arco Navo Panther Creek

Permanent RMR Exit Solutions Project TPIT Estimated Completion Date 1 RD Wells to Hickory 69kV (Denton) 06TPIT0198 (tier 4) June 2010 2 Upgrade Lewisville Switch to Highland (TNMP) 138 kV line to 290MVA or above 07TPIT0018 May 2015 3 Add second 345/138kV autotransformer at Lewisville switching substation 07TPIT0042 (tier 3) June 2011 4 Upgrade Collin to Frisco 138kV line to 326MVA 08TPIT0068 June 2013 5 Upgrade West Denton to Jim Christal to North Denton138kV line to 250 MVA or above Per E. Schroeder (TMPA) email dated 3/10/2010 Summer 2012 6 Additional capacitor banks at Navo and Panther Creek Substations (interim for Mustang capacitor bank) 2011 7 New Mustang Substation and capacitor bank 10TPIT0083 8 Upgrade Arco to Krugerville 138kV 10TPIT0032 May 2011

Questions?