Stability Issues in Entergy System

Transcription

1 Stability Issues in Entergy System Sharma Kolluri Sujit Mandal Entergy Services, Inc. TVA/NERC Stability Workshop Chattanooga, TN May 24,

2 Presentation Outline Background on Entergy Criteria Stability Problems Summary Issues/Concerns 2

3 Over 15,500 miles of transmission lines in four states 1,450 transmission substations 2.6 million customers 40,400 MW of interconnected generating plant capability Of which, 13,670 MW is uncommitted capacity Entergy s Transmission System 22,000 MW of Entergy native load plus additional 3,500 MW of wholesale & network service customer load 3

4 New Generation (EWG or QF) with Filed IOAs Since 1998 Lonoke Co. (Wrightsville) Mississippi Co. area Freeport Hot Springs Panola Co. Operational Under Construction/On Hold North AR Central Amite South WOTAB Union Co. (Panda) Ouachita Parish area Pine Bluff Warren Co. Attala Co. Choctaw Co. Hinds Co. Tenaska Baton Rouge Bogalusa As of April Beaumont/ Lake Charles New Orleans

5 Voltage Stability Criteria Limits Corresponding to Voltage Decline Criteria p.u. Voltage Limits Corresponding to 5 % margin from Nose Point Nose Point ( point before voltage collapse) LO A D > 5

6 Dynamic Voltage Stability Criteria 6

7 Generator angle (degrees) 210 Damping Criteria: 3 % Time in seconds 7

8 Areas of Stability Concern North Arkansas West of the Atchafalaya Basin (WOTAB) Western Region Voltage Stability Stability problem in WOTAB Area Export Limits Import Limits Southeast Louisiana McKnight-Franklin Flow Limits 8

9 Stability Problem in Entergy s WOTAB area 9

10 Problem Area North Arkansas Mississippi West of the Atchafalaya Basin (WOTAB) Southeast Louisiana 10

11 WOTAB Export Limits WOTAB region is a high profile industrial area accounting for ~25% of total Entergy load Two major 500kV tie lines are primary sources for WOTAB region Weber Wells 500kV line Mt. Olive Hartburg 500kV line (~180 mile long) Approximately 4,000 MW of additional generation in-service The limiting contingency is the Mt. Olive - Hartburg 500 kv line. 11

12 SABINE GRANT LASALLE NATCHITOCHES LIMESTONE LEON TEXAS NACOGDOCHES SAN AUGUSTINE HOUSTON ANGELINA SABINE ROBERTSON TRINITY VERNON RAPI DES MADISON NEWTON LOUISIANA AVOYELLES BRAZOS POLK JASPER GRIMES WALKER SAN JACINTO TYLER BEAUREGARD ALLEN EVANGELINE ST. LANDRY BURLESON JEFFERSON DAVIS HARDIN WASHINGTON WALLER MONTGOMERY LIBERTY K CALCASIEU ACADIA LAFAYETTE J CAMERON HARRIS VERMILION JEFFERSON CHAMBERS BRAZORIA GALVESTON S AB IN E RIVER 12

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15 WOTAB Export Limits 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. Major transmission improvements required to increase export limits. 15

16 WOTAB Import Limits Background Under normal operating condition, high eastwest MW flow on Weber-Wells 500kV line and low north-south MW flow on Mt. Olive Hartburg 500kV line Upon loss of Weber-Wells 500kV line, most of the flow transfer onto the 180 mile long Mt. Olive Hartburg line. This causes a severe voltage dip in WOTAB region 16

17 WOTAB Import Limits North Arkansas Mt. Olive Hartburg 500kV line Mississippi West of the Atchafalaya Basin (WOTAB) Weber Wells 500kV line 17

18 Stability limits on Mt. Olive Hartburg 500kV Line 18

19 WOTAB Import Limits Conclusions WOTAB area is susceptible to transient voltage swings under certain extreme system conditions The low voltage dynamic swings are in violation of the Entergy criteria A flow based stability limit was established on the Mt. Olive Hartburg 500kV line 19

20 McKnight-Franklin Flow Limits 20

21 Background Entergy performed a reliability upgrade on the McKnight Franklin line to raise the thermal limit from a 2000 A (1732 MVA) rating to a 3000 A (2598 MVA) rating Detailed study to assess voltage and angle stability problems was conducted to establish power flow limits under base and critical contingency conditions 21

22 Loss of Webre-Wells-Richard & Grand Gulf Franklin To Richard McKnight Webre Bogalusa Daniel Daniel-McKnight 22

23 Buf. Binary Result File Scenario Contingency Thursday, March 14, 2002, 13:41:14 6 mktfrankrating.bin Fault and Trip Mcknight-Franklin with Daniel-Mcknight O/S - Stability Index Unstable 1 -- MKT-FRK OUT Generator angle (degrees) Bus # Bus Name ID Buf G6NELSON G1RVRBN G5WGLEN WAT U NMIL U GGULF ANO U ISES U DANIST BARRY Time in seconds Mcknight-Franklin PreContingency Flow 1619 MW, 35 MVAR TSAT Transient Security Assessment Tool 23 Powertech Labs Inc. Nanjing Automation Research Institute Copyright 2002 All rights reserved

24 Wednesday, April 24, 2002, 09:38:34 Buf. Binary Result File Scenario Contingency 2 mktfrankrating.bin Fault and Trip Mcknight-Franklin with Daniel-Mcknight O/S - Damping Ratio Stable 1 -- MKT-FRK OUT Generator angle (degrees) Bus # Bus Name ID Buf G6NELSON G1RVRBN G5WGLEN WAT U NMIL U GGULF ANO U ISES U DANIST BARRY Time in seconds Mcknight-Franklin PreContingency Flow 1522 MW, 56 MVAR TSAT Transient Security Assessment Tool 24 Powertech Labs Inc. Nanjing Automation Research Institute Copyright 2002 All rights reserved

25 Results Angle Stability limits found to be 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 25

26 Voltage Stability Problem in Entergy s s Western Region 26

27 Areas of Stability Concern North Arkansas Mississippi West of the Atchafalaya Basin (WOTAB) Western Region Southeast Louisiana 27

28 Western Region Overview Conroe Network 138 kv Tie Lines 230 kv Tie Lines Woodlands Network New Caney Network Generation Load Center 28

29 Criteria Voltage (pu) Prevent UVLS activation Minimize motor tripping 29

30 Results Without motor tripping being simulated Voltage (pu) Voltage = 0.7 pu Legend Grimes Rivtrin Navasota Conroe Goslin Oakridge 30

31 Results With motor tripping being simulated Criterion for motor trip : Voltage < 0.7 pu for > 20 cycles Voltage (pu) System recovers to healthy voltages Motors Trip Legend Grimes Rivtrin Navasota Conroe Goslin Oakridge 31

32 SVC Performance Dynamic Rating Voltage (pu) Legend Grimes Rivtrin Navasota Conroe VAR output of the SVC 32

33 Overall Summary PSS installation mandatory for all new generation locating on the Entergy system Flow limits imposed to address stability issues SVCs installed to solve voltage stability problems 33

34 Stability Issues/Concerns Load Modeling static load motor load Generation Modeling and Testing Generators Exciters Governors PSS Reactive Power Margin Stability Criteria Voltage dip, Damping Ratio Tools for Real Time Stability Analysis 34