Dyess_AFB A-Sub Relay Settings.pdf

Dyess AFB

Electrical Distribution System Description

3-4

3.3.2 Available Short Circuit Current

The Utility provides the main source of short circuit currents available throughout the circuit. Refer to Table 3-1 for a summary of the available short circuit current. These values are used as the basis for the short circuit study.

Table 3-1 Utility Main Substation Short Circuit Current

Utility Short Circuit Type

Voltage Reference Fault Current

AEP Texas Alpha 69kV Line

Three Phase 69 kV 982.1 MVA

Single line to ground

69 kV 727.1 MVA

AEP Texas Bravo 69kV Line

Three Phase 69 kV 973.7 MVA

Single line to ground

69 kV 757.9 MVA

AEP Texas Charlie 69kV

Line

Three Phase 69 kV 808.9 MVA

Single line to ground

69 kV 574.6 MVA

3.3.3 Overcurrent Protection

Overcurrent protection is provided by a main breaker/relay on each feeder and/or distribution equipment. (Refer to Table 3-2, Table 3-3, and Table 3-4). For additional Neutral / Ground Overcurrent Protection settings, refer to Appendix R – Compiled OCPD Information Table.

Table 3-2 Dyess AFB Alpha Switchgear Overcurrent Protection Data

Relay FDR A1 FDR A2 Model GE SR 760 GE SR 760

CT ratio 1200/5 1200/5

Phase Settings Tap (pickup) 0.3 (360A) 0.3 (360A)

Dyess AFB Alpha Switchgear Overcurrent Protection Data

3-5

Time dial setting 1.2 1.2

Curve shape U4 Extremely Inverse

U4 Extremely Inverse

Instantaneous None None

Neutral Settings CT ratio 1000/5 1000/5

Tap (pickup) 0.15 (150A) 0.15 (150A)

Time dial setting 1.2 1.2

Curve shape U4 Extremely Inverse

U4 Extremely Inverse

Instantaneous None None

Table 3-3 Dyess AFB Bravo Switchgear Overcurrent Protection Data

Relay FDR B1 FDR B2 FDR B3 FDR B4 Model SEL-751 SEL-751 SEL-751 SEL-751

CT ratio 240/1 240/1 240/1 240/1

Phase Settings

Tap (pickup) 1.25 (173.205A)

1.25 (173.205A)

1.25 (173.205A)

1.25 (173.205A)

Time dial setting 2.85 2.85 2.85 2.85

Curve shape U3 Very Inverse

U3 Very Inverse

U3 Very Inverse

U3 Very Inverse

Instantaneous 12 (1662.77A) 15 (2078.46A) 15 (2078.46A) 10 (1385.64A)

Neutral Settings Tap (pickup) 0.5 (69.282A) 0.5 (69.282A) 0.5 (69.282A) 0.5 (69.282A)

Time dial setting 2 2 2 2

3-6

Curve shape U3 Very Inverse

U3 Very Inverse

U3 Very Inverse

U3 Very

Instantaneous None None None None

Relay RLY-S-G1-1 RLY-S-G1-2 RLY-SW-EG1-

UTILBKR

Model SEL-751 SEL-751 GE SR 750

CT ratio 240/1 240/1 1200/5

Phase Settings Tap (pickup) 2 (277.128A) 2 (277.128A) 0.68 (816A)

Time dial setting 2.5 2.5 6

Curve shape U3 Very Inverse

U3 Very Inverse

IAC Short Inverse

Instantaneous None None None

Neutral Settings Tap (pickup) 0.5 (69.282A) 0.5 (69.282A) 0.11 (132A)

Time dial setting 3.25 3.25 10.9

Curve shape U3 Very Inverse

U3 Very Inverse

U4 Extremely

Instantaneous None None None

Table 3-4 Dyess AFB Charlie Switchgear Overcurrent Protection Data

Relay FDR C1 FDR C2 FDR C3 FDR C4 Model SEL-751 SEL-751 SEL-751 SEL-751

CT ratio 120/1 120/1 120/1 120/1

Phase Settings Tap (pickup) 2.5 (300A) 2.5 (300A) 2.5 (300A) 2.5 (300A)

3-7

Time dial setting 2.85 3.23 3.1 3

Curve shape U3 Very Inverse

U3 Very Inverse

U3 Very Inverse

U3 Very Inverse

Instantaneous 29.17 (3500.4A)

29.17 (3500.4A)

29.17 (3500.4A) 29.17

(3500.4A)

Neutral Settings Tap (pickup) 1 (120A) 1 (120A) 1 (120A) 1 (120A)

Time dial setting 4.8 4.8 4.8 4.8

Curve shape U3 Very Inverse

U3 Very Inverse

U3 Very Inverse

U3 Very Inverse

Instantaneous 8.33 (999.6A)

0.2 sec Delay

8.33 (999.6A)

0.2 sec Delay

8.33 (999.6A)

0.2 sec Delay

8.33 (999.6A)

0.2 sec Delay

Relay FDR C5 FDR GPR-C- G1

FDR GPR-C-

G2

FDR IPR-C-

C7

Model SEL-751 SEL-751 SEL-751 SEL-751

CT ratio 120/1 1200/5 1200/5 1200/5

Phase Settings Tap (pickup) 2.5 (300A) 2.5 (600A) 2.5 (600A) 2.5 (600A)

Time dial setting 3 2.85 2.85 2.85

Curve shape U3 Very Inverse

U3 Very Inverse

U3 Very Inverse

U3 Very Inverse

Instantaneous 29.17 (3500.4A)

29.17 (7000.8A)

29.17 (7000.8A) 29.17

(7000.8A)

Neutral Settings Tap (pickup) 1 (120A) 1 (120A) 1 (120A) 1 (120A)

Time dial setting 4.8 4.8 4.8 4.8

3-8

Curve shape U3 Very Inverse

U3 Very Inverse

U3 Very Inverse

U3 Very Inverse

Instantaneous 8.33 (999.6A)

0.2 sec Delay

8.33 (1999.2A)

0.2 sec Delay

8.33 (1999.2A)

0.2 sec Delay

8.33 (1999.2A)

0.2 sec Delay

3.3.4 Utility Source (Substations)

Dyess Air Force Base (AFB) operates and maintains three on-site switching stations, designated Alpha, Bravo, and Charlie. These stations are powered by adjacent substations managed by American Electric Power Texas (AEP Texas). The base also features an on-site diesel generator (DG) standby plant, which is connected to the Bravo switching station. The DG plant serves as a standby power source for the main base, ensuring power supply to Bravo and Charlie in the event of a commercial power outage.

3.3.5 Switchgear Protection

At the Substation, SEL and GE relays are used for protection at the medium voltage level.

Throughout the rest of the distribution system, there is a combination of relays and fuses used for protection at the medium voltage level.

At the low voltage level, there are a combination of SSTs used. These include Sentron, Digi-Trip, Seltronic, Micrologic and Spectra RMS. Figure 3-4 shows an example of one of these relays. Some of these relays contain a ground element.

These relays fall into the Solid-State Trip (SST) category unlike an Intelligent Electronic Device (IED) category. SST provides no analytical assistance, historical databasing, or event recording.