August 7, 2003August 7, 2003Loss of Load / Generation EventLoss of Load / Generation Event

in Rio Grande Valley in Rio Grande Valley

North Edinburg

50204350

4345

5000

5010

4655

5015

5030

5035 5025

CTG1 STG3 CTG2

MVEC GEN

1400

1405

1425

1420

1415

CTG1STG3 CTG2

1410

1360

HEC GEN

HEC SS

SIMPLIFIED ONELINESIMPLIFIED ONELINE

SE Edinburg

Aderhold

SIMPLIFIED ONELINE – 14:23:15.00SIMPLIFIED ONELINE – 14:23:15.00

1) C Phase to Ground Fault – Surge Arrestor on Line Failed

North Edinburg

50204350

4345

5000

5010

4655

5015

5030

5035 5025

CTG1 STG3 CTG2

MVEC GEN

1400

1405

1425

1420

1415

CTG1STG3 CTG2

1410

1360

HEC GEN

HEC SS

37095 amps

4820 amps

18,447 amps

SE Edinburg

Aderhold

North Edinburg

50204350

4345

5000

5010

4655

5015

5030

5035 5025

CTG1 STG3 CTG2

MVEC GEN

1400

1405

1425

1420

1415

CTG1STG3 CTG2

1410

1360

HEC GEN

HEC SS

SIMPLIFIED ONELINE – 14:23:15.05SIMPLIFIED ONELINE – 14:23:15.05

1) 14:23:15.05 15:23:16N. Ed. To HEC Tripped (1)

SE Edinburg

Aderhold

SYSTEM ONELINE - 15:23:16SYSTEM ONELINE - 15:23:16

138 KV Load

138 KV LineUnit Trip

69 KV Line

69 KV Load

1) 14:23:15.05 15:23:16N. Ed. To HEC Tripped (1)

CTG2

SIMPLIFIED ONELINE – 14:23:15.59SIMPLIFIED ONELINE – 14:23:15.59

1) 14:23:15.59 15:23:18N. Ed. To HEC Closed

North Edinburg

50204350

4345

5000

5010

4655

5015

5030

5035 5025

CTG1 STG3 CTG2

MVEC GEN

1400

1405

1425

1420

1415

CTG1STG3

1410

1360

HEC GEN

HEC SS

41340 amps

12037 amps

SE Edinburg

Aderhold

North Edinburg

50204350

4345

5000

5010

4655

5015

5030

5035 5025

CTG1 STG3 CTG2

MVEC GEN

1400

1405

1425

1420

1415

CTG1STG3 CTG2

1410

1360

HEC GEN

HEC SS

SIMPLIFIED ONELINE – 14:23:15.66SIMPLIFIED ONELINE – 14:23:15.66

1) 14:23:15.66 15:23:18N Ed To HEC Tripped (2)

SE Edinburg

Aderhold

North Edinburg

50204350

4345

5000

5010

4655

5015

5030

5035 5025

CTG1 STG3 CTG2

MVEC GEN

1400

1405

1425

1420

1415

CTG1STG3 CTG2

1410

1360

HEC GEN

HEC SS

SIMPLIFIED ONELINE – 14:23:15.68SIMPLIFIED ONELINE – 14:23:15.68

1) 14:23:15.68 15:23:18 HEC STG #3 Tripped15:23:18Santa Rosa, Pharr, N. McAllen,

Polk Ave 12KV Load Tripped15:23:18Bates 69KV Tripped

SE Edinburg

Aderhold

SYSTEM ONELINE - 15:23:18SYSTEM ONELINE - 15:23:18

1) 14:23:15.68 15:23:18 HEC STG #3 Tripped15:23:18Santa Rosa, Pharr, N. McAllen,

Polk Ave 12KV Load Tripped15:23:18Bates 69KV Tripped

138 KV Load

138 KV LineUnit Trip

69 KV Line

69 KV Load

SYSTEM ONELINE - 15:23:20SYSTEM ONELINE - 15:23:20

138 KV Load

138 KV LineUnit Trip

69 KV Line

69 KV Load

1) 15:23:20Hall Acres 12KV Load Tripped

2) 15:23:20Bates 69KV Closed

SYSTEM ONELINE - 15:23:22 & 24SYSTEM ONELINE - 15:23:22 & 24

138 KV Load

138 KV LineUnit Trip

69 KV Line

69 KV Load

1) 15:23:22Bates 69KV Tripped

2) 15:23:24Pharr 12KV Load Tripped & Closed

SYSTEM ONELINE - 15:23:26SYSTEM ONELINE - 15:23:26

138 KV Load

138 KV LineUnit Trip

69 KV Line

69 KV Load

1) 15:23:26Bates 69KV Closed15:23:26S. McAllen To N. McAllen Tripped15:23:26S McAllen 12KV Load Tripped15:23:26N McAllen 12KV Load Tripped & Closed

SYSTEM ONELINE - 15:23:28SYSTEM ONELINE - 15:23:28

138 KV Load

138 KV LineUnit Trip

69 KV Line

69 KV Load

1) 15:23:28Hall Acres 12KV Load Tripped15:23:28S. McAllen To N. McAllen Closed

North Edinburg

50204350

4345

5000

5010

4655

5015

5030

5035 5025

CTG1 STG3 CTG2

MVEC GEN

1400

1405

1425

1420

1415

CTG1STG3 CTG2

1410

1360

HEC GEN

HEC SS

39813 amps

7170 amps

SIMPLIFIED ONELINE – 14:23:25.65SIMPLIFIED ONELINE – 14:23:25.65

1) 14:23:25.65 15:23:30N. Ed. To HEC Closed14:23:25.74 15:23:30N. Ed to HEC Tripped (3)14:23:25.76 15:23:30N. Ed. To MVEC Tripped (CTG1)

SE Edinburg

Aderhold

North Edinburg

50204350

4345

5000

5010

4655

5015

5030

5035 5025

CTG1 STG3 CTG2

MVEC GEN

1400

1405

1425

1420

1415

CTG1STG3 CTG2

1410

1360

HEC GEN

HEC SS

SIMPLIFIED ONELINE – 14:23:25.74SIMPLIFIED ONELINE – 14:23:25.74

1) 14:23:25.65 15:23:30N. Ed. To HEC Closed14:23:25.74 15:23:30N. Ed to HEC Tripped (3)14:23:25.76 15:23:30N. Ed. To MVEC Tripped (CTG1)

SE Edinburg

Aderhold

North Edinburg

50204350

4345

5000

5010

4655

5015

5030

5035 5025

CTG1 STG3 CTG2

MVEC GEN

1400

1405

1425

1420

1415

CTG1STG3 CTG2

1410

1360

HEC GEN

HEC SS

SIMPLIFIED ONELINE – 14:23:25.76SIMPLIFIED ONELINE – 14:23:25.76

1) 14:23:25.65 15:23:30N. Ed. To HEC Closed14:23:25.74 15:23:30N. Ed to HEC Tripped (3)14:23:25.76 15:23:30N. Ed. To MVEC Tripped (CTG1)

SE Edinburg

Aderhold

SYSTEM ONELINE - 15:23:30SYSTEM ONELINE - 15:23:30

1) 14:23:25.65 15:23:30N. Ed. To HEC Closed14:23:25.74 15:23:30N. Ed to HEC Tripped (3)14:23:25.76 15:23:30N. Ed. To MVEC Tripped (CTG1)

138 KV Load

138 KV LineUnit Trip

69 KV Line

69 KV Load

SYSTEM ONELINE - 15:23:38SYSTEM ONELINE - 15:23:38

1) 15:23:38Various 12KV Feeders Tripping &Closing over 15 Minute period.

138 KV Load

138 KV LineUnit Trip

69 KV Line

69 KV Load

North Edinburg

50204350

4345

5000

5010

4655

5015

5030

5035 5025

CTG1 STG3 CTG2

MVEC GEN

1400

1405

1425

1420

1415

CTG1STG3 CTG2

1410

1360

HEC GEN

HEC SS

SIMPLIFIED ONELINE – 14:37:21.97SIMPLIFIED ONELINE – 14:37:21.97

1) 14:37:21.97 15:37:30MVEC CTG2 Tripped

SE Edinburg

Aderhold

North Edinburg

50204350

4345

5000

5010

4655

5015

5030

5035 5025

CTG1 STG3 CTG2

MVEC GEN

1400

1405

1425

1420

1415

CTG1STG3 CTG2

1410

1360

HEC GEN

HEC SS

SIMPLIFIED ONELINE – 14:37:28.94SIMPLIFIED ONELINE – 14:37:28.94

1) 14:37:28.94 MVEC STG3 Tripped

SE Edinburg

Aderhold

SYSTEM ONELINE - 15:37:30 & 15:45SYSTEM ONELINE - 15:37:30 & 15:45

10) 14:37:21.97 15:37:30MVEC CTG2 Tripped16) 14:37:28.94 MVEC STG3 Tripped 17) 15:45 Found blown Surge Arrester

at North Edinburg

138 KV Load

138 KV LineUnit Trip

69 KV Line

69 KV Load

HEC GTG1 (1)HEC GTG1 (1)

-8.4 MVARS +135.9 MVARS

HEC GTG2 (1)HEC GTG2 (1)

+81 MVARS +190.5 MVARS

HEC STG3 (1)HEC STG3 (1)

+10.2 MVARS -109.7 MVARS

MVEC CTG1 (1)MVEC CTG1 (1)

+176 MVARS +370 MVARS

Total Load LossTotal Load Loss

Approximately 375 MW of load loss.

(From 4650 MW to 4275 MW.)

1) Two AEP Totalizers Tripped

Feeder Trip SummaryFeeder Trip Summary

300 amps

100 amps 100 amps 100 amps

2) 22 AEP Feeders Tripped across Valley

3) Sympathetic Tripping -most by ground over current, a few by under voltage relay

Transmission Issues FoundTransmission Issues Found

1) 138 KV N. Ed 1 reclosed one more time than design

Found wrong setting on SEL279 & Corrected

2) 138 KV N. McAllen to S. McAllen Overtripped

Found closed ground switch on carrier & Corrected

3) 69KV Bates to N. Ed Tripped

Blown PT fuse replaced.

4) North Alamo Totalizer Ground tripped due to Sypathetic Trip

Ground settings reviewed and increased

5) Polk Ave Totalizer Ground tripped due to Sypathetic Trip

Ground settings reviewed and increased