Download Mt. Olive-Hartburg for Weber-Wells Flowgate Restudy Update

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
Voltage Dip Criteria
Improve
post-fault
voltage
Minimize
motor
tripping
Study Results
Case No.
1
2
3
Case Description
1.With Firm Transaction
2.Nelson U6 off-line
1.With Firm Transaction
2.Nelson U6 off-line
1.With Firm Transaction
2.Nelson U6 off-line
Post Contignecy Flow on
Mt.Olive – Hartburg 500kV
line (MW)
Post Contignecy Steady State
Voltage at Hartburg 500kV
Bus (p.u.)
Lowest Bus Voltage Dip &
Swing in WOTAB area
Max Dip: 0.62p.u.
1260
0.968
Duration of Dip <0.80p.u.: 50 Cycles
Max Dip: 0.699p.u.
1150
0.986
Duration of Dip <0.80p.u.: 38 Cycles
Max Dip: 0.75p.u.
1045
0.998
Duration of Dip <0.80p.u.: 27 Cycles
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
Dynamic Simulation Plot
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