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Update on Flowgate Stability Limit Study. Entergy Transmission AFC Stakeholder Meeting Houston, TX September 19, 2006. Problem Definition.
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Update on Flowgate Stability Limit Study Entergy Transmission AFC Stakeholder Meeting Houston, TX September 19, 2006
Problem Definition • The stability limit on the Mt. Olive – Hartburg line defines the maximum MW flow level that can be accommodated on the Mt. Olive – Hartburg line upon the contingency of the Webre – Wells line
Study Purpose • To review the existing flowgate limit on the Mt. Olive – Hartburg 500 kV line • Perform sensitivity studies to determine if the MW rating of the line could be increased • Evaluate solutions/options to improve the flow gate limit
Study Assumptions • Peak case • 2006 summer peak case • Load power factor in WOTAB is 0.945 • IPP units in WOTAB are turned on based on the status of firm transmission service • Nelson unit 6 or Sabine unit 4 is out of service in the base case • WSCC Criteria applied for voltage dip
Improve post-fault voltage Minimize motor tripping Voltage Dip Criteria
Sensitivity Study • Peak Case • With Nelson Unit 6 on-line at minimum generation (MW) • With Sabine unit 4 on-line at minimum generation (MW) • Off-Peak case • 2005 Winter Case • Load power factor in WOTAB is 0.95 • Entergy and IPP units in WOTAB area are dispatched based on historical information • Post Contingency Flow on Mt. Olive – Hartburg line is 1250 MW
Sensitivity Study Results • Dispatch of Nelson Unit 6 or Sabine Unit 4 has negligible impact on the Mt. Olive – Hartburg 500kV stability limit • Variation in load levels in WOTAB area has very little impact on the Mt. Olive – Hartburg 500kV stability limit
Solution Options • SVC Option • Peak case • 300MVAR SVC at Hartburg 500 & 230kV stations • Series Compensation Option • Peak case • 50% Series Compensation on Mt. Olive – Hartburg 500kV Line Results of Options Evaluated: • 300MVAR SVC at Hartburg 500 kV and 230kV stations do not yield an improvement in the stability limit • Series compensation has the potential to improve the stability limit
Study Summary • Sensitive studies indicate that stability limit on Mt. Olive - Hartburg 500kV line is not affected by generation dispatch and load changes in WOTAB area • Series compensation can improve stability limit on Mt. Olive - Hartburg 500kV line • Entergy will further evaluate this option in their planning process • The flowgate limit will continue to be set to 1050 MW