Transcript Willow Glen Short Circuit Study

Stability Issues in Entergy
System
Entergy Transmission Planning Summit
New Orleans, LA
July 10, 2003
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Classification of Power System Stability
• Transient/Angle Stability
• Voltage Stability
• Small Signal/Oscillatory Stability
2
Static Voltage Stability Criteria
Limits Corresponding to Voltage Decline Criteria
0.988
0.968
0.948
0.928
0.908
0.888
Limits Corresponding to 5 % margin from Nose Point
0.848
0.828
0.808
0.788
0.768
0.748
Nose Point ( point before
voltage collapse)
0.728
0.708
0.688
0.668
LOAD ------->
3
640
590
540
490
440
390
340
290
240
0.648
190
p.u. Voltage
0.868
Dynamic Voltage Stability Criteria
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Thursday, March 14, 2002, 13:39
Buf.
Binary Result File
Scenario
Contingency
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mktfrankrating.bin
Fault and Trip Mcknight-Franklin - Damping Ratio
Stable 1 -- MKT-FRK OUT
Damping Criteria – 3 %
Generator angle (degrees)
210
144
Bus #
Bus Name
ID Bu
97915
98231
98245
98538
98605
98954
99489
99820
96876
96475
G6NELSON
G1RVRBN
G5WGLEN
WAT U3 25.0
NMIL U5 20.0
GGULF
ANO U2 22.0
ISES U2 22.0
DANIST4 13.8
BARRY 526.0
1
1
1
1
1
1
1
1
4
5
78
12
-54
-120
0.000
4.000
8.000
12.000
16.000
20.000
Time in seconds
5
Powertech Labs Inc.
Nanjing Automation Research Institute
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Areas of Stability Concern in 2002
I. Joint Stability Study between
North Arkansas
Entergy, Southern, and TVA
Northwest
Quadrant
West of the Atchafalaya Basin
(WOTAB)
Southeast Louisiana
II. McKnight-Franklin Flow
Limits
III. Stability problem in WOTAB Area
6
I. Joint Stability Study between
Entergy, Southern, and TVA
7
Results/Northwest Quadrant
• New generation added without PSS severely
deteriorated system damping.
• The most limiting contingency from a damping
standpoint was the Miller - Bellefonte 500 kV line.
• The most limiting contingency from a voltage
standpoint was the Farley - Mitchell 500 kV line.
• With PSS on new generating units, the export limits
were found to be 3,850 MW.
• Current Status: Problem doesn’t exist any more due
to cancellation of some IPP generation.
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II. McKnight-Franklin Flow Limits
9
Problem Area
North Arkansas
Mississippi
West of the Atchafalaya Basin
(WOTAB)
Southeast Louisiana
10
Results/Southeast Louisiana
• Angle Stability limits found to be slightly lower
than voltage stability limits
• Rating of the McKnight-Franklin 500kV line
limited to 2,070 MVA due to unacceptable
damping
– With Webre-Richard out of service, the flow limit is 1,958
MVA
– With Daniel-McKnight out of service, the flow limit is 1,522
MVA
• No transient voltage security violations
observed
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III. Stability Problem in Entergy’s
WOTAB area
12
Problem Area
North Arkansas
Mississippi
West of the Atchafalaya Basin
(WOTAB)
Southeast Louisiana
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Results/WOTAB
• The limiting contingency is the Mt. Olive - Hartburg
500 kV line.
• Without PSS, the limit is 2,700 MW based on damping
criteria ( < 3% damping).
• With PSS on new generating units, the export limit
was found to be 3300 MW based on voltage collapse
criteria.
• Limit based on voltage decline criteria (0.92 pu) is
2,100 MW.
• Major transmission improvements may be required to
increase export limits.
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New Areas of Stability Concern
North Arkansas
Mississippi
West of the Atchafalaya Basin
(WOTAB)
Southeast Louisiana
V. Western Region
Voltage Stability
IV. Amite South Stability
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IV. Stability Problem in Entergy’s
Amite South Area
16
Problem Area
North Arkansas
Mississippi
West of the Atchafalaya Basin
(WOTAB)
Southeast Louisiana
Amite South Region
17
Background
• Major Load Center
• Large Concentration of Generation
• Expected 2003 conditions:
– 6,280 MW of load (including CLECO & LaGEN
loads)
– 8,400 MW of native and new generation
18
Background
• 230 kV loop out of Waterford is critical
– Approximately 3,100 MW generation in the loop
– System stable for primary clearing faults
– Additional generation can lead to instability for
stuck breaker faults
19
Results
• Under stuck breaker faults
– Fault clearing time very important for the stability
of the region
– Units in Amite south region and close vicinity can
separate from the rest of the system
– Can lead to lines tripping
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System Separation
21
Solutions Proposed
• Faster fault clearing devices (relays, breakers)
• Remedial action scheme to trip certain units to
protect against stuck breaker fault conditions
• Power system stabilizers on the new units
• IPO breakers
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V. Voltage Stability Problem in
Entergy’s Western Region
23
Areas of Stability Concern
North Arkansas
Mississippi
West of the Atchafalaya Basin
(WOTAB)
Southeast Louisiana
Western Region
24
Background
• Western Region load growth: ~ 5.1 %
• Generation sources: Two Lewis Creek units
(226MW & 230MW, 150 MVAR each)
• With one Lewis Creek unit out of service,
certain line outages can cause low voltages
leading to potential voltage collapse.
• Critical tie lines are Grimes – Crockett 345 kV
and China – Jacinto 230 kV.
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Background
• Currently, Under Voltage Load Shedding (UVLS)
scheme is in place.
– Voltage at critical buses below 0.92 pu
– Loss of both Lewis Creek generators
– Lewis Creek units go into over excitation mode
• Series Compensation on China – Jacinto 230 kV line
• Static capacitors installed – 770 MVAR
• Two D-SMES units (8 MVA each) installed at New
Caney and Metro in 2001
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Power – Voltage (P-V) Curve
Loss of one Lewis Creek unit and Grimes – Crockett 345 kV line
1.04
1.02
Metro138
Conroe138
Lewis138
Tamina138
1
Voltage (P.U.)
Goslin138
Jacinto138
Jacinto230
0.98
NAVSOTA138
Grimes138
CALVERT69
0.96
NewCaney138
Rivtrin138
Dayton138
0.94
0.92
1300.00
Cypress138
1350.00
1400.00
1450.00
1500.00
Western Region Load Level (MW)
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1550.00
1600.00
Voltage Profile at Critical Buses
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Results for 2005 Summer Peak
• Voltage Instability
– Slow voltage recovery
– Several motor loads at risk
– Depressed voltages can lead to UVLS operation
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Possible Solutions
• Static Devices – MS Shunt Cap Banks
• Series Compensation
• New transmission facilities (for details, see
EGSI-TX’s area planning presentation)
• Dynamic VAR support device (e.g., SVC,
STATCOM, D-SMES)
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System Stability Summary
• PSS installation mandatory for all new generation
locating on the Entergy system
• PSS tuning mandatory in WOTAB and Southeast
Louisiana
• Traditional methods are needed to fix stability
problems (alleviate thermal constraints, additional
static reactive power support devices, series
compensation)
• New technologies (FACTS devices, e.g., SVC,
STATCOM, D-SMES, UPFC, etc.) may be required.
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