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CREZ Panhandle Study Update Sharyland Utilities

CREZ Panhandle Study Update Sharyland Utilities. May 20, 2014. Background. In parallel with the ERCOT PREZ Study, Sharyland has been evaluating the transmission system performance in the Panhandle region, specifically:

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CREZ Panhandle Study Update Sharyland Utilities

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  1. CREZ Panhandle Study UpdateSharyland Utilities May 20, 2014

  2. Background In parallel with the ERCOT PREZ Study, Sharyland has been evaluating the transmission system performance in the Panhandle region, specifically: • Including generation resources meeting Section 6.9 of the ERCOT Planning Guides • Completing steady state voltage security, transient voltage stability and system strength assessments for the Panhandle region with updated generation models • Including the trigger levels identified in the ERCOT PREZ study report • Evaluating the assumptions of the 2400 MW Panhandle export limit and the corresponding 2,160 MW used in the ERCOT economic study

  3. Preliminary Sharyland Study Conclusions • Based on updated WGR locations and sizes (that meet Section 6.9 of the ERCOT Planning Guides), no stability concerns were observed for 3,263 MW • Under 2014 case simulations the as-is CREZ transmission system observed to be able to accommodate 3,263MW of WGR capacity meeting Section 6.9 of ERCOT Planning Guide • No concerns observed from a steady state voltage security, voltage stability and/or system strength standpoint (no control instability or sustained oscillations) • Sharyland utilized a Composite Short Circuit Ratio (CSCR) approach to evaluate “optimal” amount of SCs required for conditions studied • Comparative analysis performed between the CSCR & ERCOT’s proposed WSCR approach – both approaches observed to yield similar results • Sharyland deems it important to investigate the “technical basis/justification” for the WSCR threshold – SC requirements are very sensitive to the target • Also important to differentiate between WSCR and the SCR requirements at the POI for turbine vendors

  4. Preliminary Sharyland Study Conclusions • Under 2015 system conditions, Sharyland finds the 2nd circuit along with properly sized and placed condensers provide adequate support for 4,545 MW (units meeting Section 6.9 & signed IAs with COD of 2014/15). • The 2nd circuit addition observed to be the “common requirement” from a voltage stability perspective • SCs provide limited incremental voltage support benefit – system strength key driver for SC sizing • Sharyland performed optimization studies for the best locations for SCs • 250 MVAr of SCs at two Sharyland substations, along with 2nd circuit, perform adequately for 4,545 MW of Panhandle exports • Results corroborated by dynamic simulations also • Prior loss of an SC followed by an ERCOT N-1 event results in control instability for the loss of large SC devices – not an issue with modular SCs

  5. Panhandle WGRs meeting Section 6.9 of ERCOT Planning Guide (May 2014)

  6. WGR Survey • Sharyland surveyed generation developers asking for updated phasing and commercial operation schedules for their panhandle wind projects • SGIA commercial operations dates (COD) were used for wind projects connected to WETT and CTT • Survey results below are for units that have met Planning Guide 6.9 requirements

  7. Dynamic Simulation Study Scenarios Scenario Definitions, Dynamic Simulations – SU Panhandle Assessment

  8. Dynamic Simulation Results Dynamic Simulations Results Summary – SU Panhandle Assessment

  9. Questions ?

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