crez panhandle study update sharyland utilities

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CREZ Panhandle Study UpdateSharyland UtilitiesMay 20, 2014

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BackgroundIn 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

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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

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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

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

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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

Q3 - 2014 Q4 - 2014 Q1 - 2015 Q2 - 2015 Q3 - 2015 Q4 - 2015822 1712 1762 2255 2703 3263

Cumulative MW Totals by Quarter (MWs) - Total Panhandle

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Dynamic Simulation Study Scenarios

SU Panhandle Loop Total Panhandle

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Base Case with Panhandle WGRs meeting Section 6.9 of Planning Guide

855 3263 None

2-a 1287 4545 2nd circuit on SU Loop

2-b 1287 4545 Large SC (320/250) @ WM/OG

2-c 1287 4545 Large SC (320/250) @ AB/WM

2-d 1287 4545 Large SC (320/250) @AB/TC

2-e 1287 4545 2nd circuit on SU Loop & Large SC (320/250) @WM/OL

2-f 1287 4545 2nd circuit on SU Loop and 50/50 SCs on WM/OL

2-g 1287 4545 2nd circuit on SU Loop and 100/100 SCs on WM/OL

2-h 1287 4545 2nd circuit on SU Loop and 100/100 SCs on TC/AB

2-i 1287 4545 2nd circuit on SU Loop and 150/100 SCs on AB/TC

2-j 1287 4545 2nd circuit on SU Loop and 100/150 SCs on AB/TC

Scenario #

2015 Case with Panhandle WGRs meeting Section 6.9 & Ias with COD of 2015

Scenario DescriptionPanhandle MW Capacity

Transmission Upgrades

Scenario Definitions, Dynamic Simulations – SU Panhandle Assessment

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Dynamic Simulation Results

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Base Case with Panhandle WGRs meeting Section 6.9 of Planning Guide

None Stable

2-a 2nd circuit on SU Loop Unstable

2-b Large SC (320/250) @ WM/OG Unstable

2-c Large SC (320/250) @ AB/WM Unstable

2-d Large SC (320/250) @AB/TC Unstable

2-e 2nd circuit on SU Loop & Large SC (320/250) @WM/OL Stable

2-f 2nd circuit on SU Loop and 50/50 SCs on WM/OL Unstable

2-g 2nd circuit on SU Loop and 100/100 SCs on WM/OL Sustained Oscillation

2-h 2nd circuit on SU Loop and 100/100 SCs on TC/AB marginally Stable

2-i 2nd circuit on SU Loop and 150/100 SCs on AB/TC Stable

2-j 2nd circuit on SU Loop and 100/150 SCs on AB/TC Stable

Scenario #

2015 Case with Panhandle WGRs meeting Section 6.9 & Ias with COD of 2015

Scenario Description Transmission Upgrades Key Observations

Dynamic Simulations Results Summary – SU Panhandle Assessment

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Questions ?

crez panhandle study update sharyland utilities

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