ERCOT RMR Study for Luminant NSO Jeff Billo RPG Meeting March 13, 2009

Luminant – Notice of Suspension of Operations On February 5, 2009 Luminant submitted Notice of Suspension of Operations (NSO) for: March 13, 2009 RPG Meeting

Luminant – Notice of Suspension of Operations The units were grouped and analyzed in two group based on the proposed suspension dates Group 1: May 2009 Group 2: September 2009 Analysis was done to determine if absence of the units violated any planning criteria as outlined in the Operating Guides Transfer study performed using MUST Voltage Stability study performed using VSAT Study results were reviewed and verified by Operations Staff March 13, 2009 RPG Meeting

Luminant – Notice of Suspension of Operations The following study assumptions were used: 2009 summer peak case (SSWG DSA December 2008 Update) used for Group 1 units All Group 1 units turned off All Group 2 units were available (unless otherwise specified) All wind generation was turned off 2010 summer peak case (SSWG DSB December 2008 Update) used for Group 2 units All Group 1 and 2 units were turned off For each unit a second scenario was modeled where a nearby unit was modeled as unavailable; for some units a third scenario was modeled where a different nearby unit was modeled as unavailable [to meet Operating Guide 5 requirements] March 13, 2009 RPG Meeting

Luminant – Notice of Suspension of Operations Justification for turning off wind generation in RMR analysis using 2008 wind data 348 hours when wind generation was less than 10% of installed capacity (roughly one hour each day) 179 hours when all wind generation in ERCOT was less than 30 MW total (roughly one hour every 2 days) 55 hours when all wind generation in ERCOT was less than 10 MW (roughly one hour each week) 1 hour when all wind generation in ERCOT was 0 MW March 13, 2009 RPG Meeting

Luminant – Notice of Suspension of Operations Permian Basin 5 Results With a nearby unavailable the following constraints could not be resolved: Transfer Limit (MW) Limiting Element Limiting Contingencies -483 Odessa (138/345) kV Auto-transformer – 1 Auto-transformer – 2 -118 Ackerly Vealmoor – Ackerly 69 kV Line Sharon Ridge – Bluff Creek 138 kV Line March 13, 2009 RPG Meeting

Luminant – Notice of Suspension of Operations Permian Basin 6 Results The following constraints could not be resolved: Transfer Limit (MW) Limiting Element Limiting Contingencies -56.1 1027 ODESEHV_ 138 1028 ODESEHV_ 345 1 1027 ODESEHV_ 138 1028 ODESEHV_ 345 2 412.3 March 13, 2009 RPG Meeting

Luminant – Notice of Suspension of Operations Permian Basin 6 Results With a nearby unit unavailable the following constraints could not be resolved: Transfer Limit (MW) Limiting Element Limiting Contingencies -122.5 1356 ACKRLYVE 69.0 1362 ACKERLY_ 69.0 1 1300 EXSHARNR 138 1309 BLUFCKTA 138 1 150.2 1362 ACKERLY_ 69.0 1363 ACKRLNTC 69.0 1 210.5 1300 EXSHARNR 138 1301 WILLOWVA 138 1 201.8 1308 GAILLYNT 138 1301 WILLOWVA 138 1 280.0 272.2 401.4 1363 ACKRLNTC 69.0 1364 SPARNBRG 69.0 1 409.9 1164 LAMESA_9 69.6 1364 SPARNBRG 69.0 1 1027 ODESEHV_ 138 1028 ODESEHV_ 345 1 1027 ODESEHV_ 138 1028 ODESEHV_ 345 2 346.1 459.2 1054 OLFNNSHL 138 1055 NYLONTAP 138 1 1051 HUNTSMAN 138 1052 REXALL_8 138 1 269 1322 BIGSPRIG 138 1324 BIGSPGWE 138 1 1028 ODESEHV_ 345 11016 QUAILSW_ 345 1 1030 MRGNCRK_ 345 1058 LONGSHOR 345 1 March 13, 2009 RPG Meeting

Luminant – Notice of Suspension of Operations Decordova Results With a nearby unit unavailable the following constraints could not be resolved: Transfer Limit (MW) Limiting Element Limiting Contingencies -981 2427 WATMLL_W 345 3123 TRINDAD1 345 1 Limestone 345 kV to Water Mill 345 kV 1 Limestone 345 kV to Water Mill 345 kV 2 -57.2 3380 BIGBRN__ 345 3391 JEWETT_N 345 1 -287 2432 TRICRN1_ 345 3124 TRINDAD2 345 1 228.5 2420 CHILSW1_ 345 2428 WATMLL_E 345 1 2398 WLEVEE1_ 345 2997 WATMLL_2 345 1 2427 WATMLL_W 345 2946 SARGT1_5 345 1 2427 WATMLL_W 345 2997 WATMLL_2 345 1 473.1 1906 VENUS_S5 345 3380 BIGBRN__ 345 1 March 13, 2009 RPG Meeting

Luminant – Notice of Suspension of Operations Further analysis is being done to determine if Permian Basin 5, Permian Basin 6, and Decordova are needed as Reliability Must Run (RMR) units. Uplan analysis being performed to determine if security constrained dispatch is possible Working with Oncor to verify results and possibly determine if RAPs or SPSs can be developed to resolve constraints Initial analysis determined that all other units proposed in the NSO did not qualify for RMR status. March 13, 2009 RPG Meeting

Questions? March 13, 2009 RPG Meeting