Attachment 17 VA Med Center El Paso Power Analysis RPT.pdf

Cover Page

Power System Analysis VA Medical Health Care

El Paso, TX

Power System Engineering

COVER LETTER

COVER PAGE

POWER SYSTEM ANALYSIS

VA Medical Health Care El Paso, TX

Prepared by Marsela Jakub-Wood under the supervision and direct control of

Schneider Electric Engineering Services, LLC Texas Firm No. F-10107

Job Number Rev. Date Description Prepared By S4: 50753956 - November 12, 2024 SC & TCC MJ

1 - - - 2 - - -

This document has been authorized for release by the engineer whose seal and signature are hereto affixed. Altering this document is unlawful unless performed by or under the direction of a licensed professional engineer. Any changes shall be described and the engineer authorizing such alterations shall seal, sign, and date the revised document.

For Information, contact StudiesSupport.PSE@se.com

FILE: VA Med Center El Paso

11/13/2024

DISCLAIMER

The following report was prepared by the Power System Engineering group of Schneider Electric Engineering Services, LLC (SEES) utilizing industry-accepted standards and practices. Data used in this analysis was acquired by Power System Engineering and provided by others, through onsite discovery, published information, equipment nameplates, manufacturer ratings, testing, analysis, or other means.

SEES assumes no responsibility for inaccuracies in data provided by others. The study is intended for use by qualified individuals to facilitate the installation, operation, maintenance, and safety of the electrical power system depicted. Modification of equipment, changes to system configuration, adjustment of protective device settings, or failure to properly maintain equipment may invalidate these results.

The stylized trademarks “Square D” and “Schneider Electric” and any other trademarks and trade names that are the property of Schneider Electric USA, Inc are used by permission.

TABLE OF CONTENTS

1 EXECUTIVE SUMMARY

1.1 OVERVIEW

1.2 REVISION HISTORY

1.3 STUDY RECOMMENDATIONS

1.4 STUDY HIGHLIGHTS

1.4.1 SHORT-CIRCUIT

1.4.2 COORDINATION

1.4.3 ARC FLASH

2 INTRODUCTION

3 STUDY DATA

3.1 IMPORTANCE

3.2 MISSING DATA

3.3 ESTIMATES & ASSUMPTIONS

4 SHORT-CIRCUIT ANALYSIS

4.1 GENERAL PROCEDURE

4.2 DATA USED IN THE CALCULATIONS

4.2.1 POWER COMPANY DATA

4.2.2 GENERATOR DATA

4.2.3 CABLE DATA

4.2.4 TRANSFORMER DATA

4.2.5 MOTOR CONTRIBUTION TO SHORT-CIRCUIT CURRENT

4.3 SHORT-CIRCUIT ANALYSIS RESULTS

4.4 SHORT-CIRCUIT EVALUATION TABLE

5 OVERCURRENT DEVICE COORDINATION ANALYSIS

5.1 GENERAL PROCEDURE

5.2 SPECIFIC PROCEDURE

5.2.1 SHORT-CIRCUIT CURRENT CONSIDERATIONS

5.2.2 MOLDED CASE BREAKER COORDINATION

5.2.3 LOW-VOLTAGE GROUND-FAULT SETTINGS

5.2.4 TRANSFORMER PROTECTIVE DEVICES

5.2.5 CABLE PROTECTION

5.2.6 SELECTIVE COORDINATION AND THE NATIONAL ELECTRICAL CODE

5.3 OVERCURRENT DEVICE COORDINATION ANALYSIS RESULTS

5.4 OVERCURRENT DEVICE SETTING TABLE

5.5 TIME-CURRENT COORDINATION GRAPHS - AS FOUND SETTINGS

5.6 TIME-CURRENT COORDINATION GRAPHS – RECOMMENDED SETTINGS

6 ARC FLASH HAZARD ANALYSIS

APPENDIX A: ABBREVIATIONS AND TRADEMARKS

APPENDIX B: SHORT CIRCUIT INPUT/OUTPUT DATA

APPENDIX C: REFERENCES

APPENDIX D: SYSTEM STUDY ONE-LINE DIAGRAMS

1 EXECUTIVE SUMMARY

1.1 Overview

This report documents the results of a Power System Engineering analysis for the VA Medical Health Care in El Paso, TX. The objective of this section is to briefly summarize the results of the analysis and highlight key issues and findings in the electrical distribution equipment. For items addressed by equipment, conductor, or device settings changes, the power system study results may need to be re-evaluated in a revision to this study. The full analysis can be found in the main body of the report.

The scope of this study is limited to that equipment shown on the study one-line diagrams located in the back of the report. Packaged end-use equipment (e.g., elevators, HVAC, etc.) should be installed per manufacturer requirements, and the sizing of the maximum overcurrent protection (MOCP) device and wiring based on minimum circuit ampacity (MCA) is outside the scope of this study.

Data for this study was obtained from the following sources:

1. Data collection completed by PDM on 8/19/2024 – 9/24/2024

2. Previous power system study completed by Schneider Electric on 1/23/2024 under project number 43690218.

3. Previous power system study completed by Schneider Electric on 2/18/2015 under project number 34801189.

4. Previous power system study completed by SSOE. Partial report was provided for the 2015 study.

1.2 Revision History

This section will document revision history after the initial study has been submitted.

Subsequent revision numbers are each listed on the front cover of the report and are explained below by indicating the following details: date of issue, reason for revision, and who initiated the revision. When necessary, engineer’s comments and/or pertinent emails will be referred to in the references section of the report.

1.3 Study Recommendations

Priority Guidance for Recommendations:

High – Recommendations related to potential NEC violations, safety, meeting customer specifications, or data required to complete analyses. Changes are often needed.

Medium – Recommendations related to general improvements, system performance, or issues that are unclear at time of study. Changes are sometimes needed.

Low – General comments/notes. Changes are rarely needed.

VA Medical Healthcare

El Paso, TX

Q2C: 50753956

POWER SYSTEM ENGINEERING

Item # Priority Description Reference Recommendation

1 High Missing Data Section 3.2 Provide data listed in Section 3.2

2 High Coordination ‐ NEC 517 Health Care (above

0.1 sec)

TCC 2205 ‐ PNL 1DCHA

ETCC 2206 ‐ PNL 2HC

ETCC 2220 ‐ S. CRIT BUS

ETCC 2924 ‐ PNL MPPAE

ETCC 2933 ‐ PNL MPPBE

TCC 2942 ‐ PNL D1DNL

TCC 2610 ‐ N. CRIT BUS

Study used SSOE study to obtain breaker information for these circuits. Confirm breaker modeled in the study reflect actual breakers installed.

3 High Coordination ‐ NEC 517 Health Care (above

0.1 sec)

TCC 2010 ‐ PNL MP2CC

TCC 2015 ‐ PNL MP3CC

TCC 2020 ‐ PNL MP4CC

Replace the following breakers:

Panel MP1CC:

Replace (3) thermal‐magnetic 225A JD breaker with JD

250AS/225AT Micrologic LI trip unit

Panel MP2CC:

Replace thermal‐magnetic 225A JD main breaker with JD

250AS/225AT Micrologic LI trip unit

Panel MP3CC:

Replace thermal‐magnetic 225A JD main breaker with JD

250AS/225AT Micrologic LI trip unit

Panel MP4CC:

Replace thermal‐magnetic 125A HD main breaker with HD

150AS/125AT Micrologic LI trip unit

4 High Coordination ‐ NEC 517 Health Care (above

0.1 sec)

ETCC 2410 ‐ PNL MP1CE

TCC 2660 ‐ 4BCLB

Increase device trip ratios and/or change circuit breakers to electronic trip unit type. Other options may be redistributing loads to reduce zones of protection. Contact study engineer for guidance.

5 High Coordination ‐ NEC 517 Health Care (above

0.1 sec)

TCC 2520 ‐ PNL MP2CE

Replace the following breakers:

Panel D1DQH:

Replace 400AF/200AT SGHA breaker with electronic trip breaker.

6 High Coordination ‐ NEC 517 Health Care (above

0.1 sec)

TCC 2225 ‐ PNL 2ACLA

TCC 2240 ‐ PNL 3ACLA

Replace the following breakers:

PNL 2ACLA:

Replace thermal‐magnetic 100A HD main breaker with HD

100AS/100AT Micrologic LI trip unit

PNL 3ACLA:

Replace thermal‐magnetic 100A QD main breaker with HD

100AS/100AT Micrologic LI trip unit

Study used SSOE study to obtain breaker information for the busplugs. Confirm breaker modeled in the study reflect actual breakers installed. If no changes were made since the

SSOE study, then further breaker replacement will be required.

7 High Coordination ‐ NEC 517 Health Care (above

0.1 sec)

Multiple breakers with recommended settings marked in RED in the settings table

In order to achieve selectivity, multiple breakers in the

Essential Electrical System require breaker setting adjustment. Implement recommended settings to comply with the selective coordination requirements.

8 High Coordination ‐ NEC 517 Health Care (above

0.1 sec)

TCC 2620 ‐ PNL 1BCLA

Replace the following breakers:

Panel 1BCLA:

Replace thermal‐magnetic 60A HG main breaker with HD

100AS/60AT Micrologic LI trip unit

RECOMMENDATIONS TABLE

#Public

El Paso, TX

Q2C: 50753956

POWER SYSTEM ENGINEERING

Item # Priority Description Reference Recommendation

RECOMMENDATIONS TABLE

9 High NEC 240.4 ‐ Cables not protected

Cable29‐ ATS‐CR1 to 1DCHA

Cable3‐ MSA toD3XHA

Cable40‐ ATS‐LS to 1DLHA

Cable48‐ MSB to ATS‐EQ2

Cable49‐ ATS‐EQ2 to D1DQH

Cable56‐ SC BUSWAY to 1BCHA

Cable57 ‐ X1BC to 1BCLA

Cable75‐ 2BNLD to 2BNLA

Cable82‐ MSA to ATS‐EQ5

Cable83‐ ATS‐EQ5 to 1DEHA

Cable90‐ EDS to ATS‐EQ5

Cable7‐ X4AN to D4ANL

Verify cable size and upstream breaker information.

Increase cable size or reduce circuit breaker trip to meet protection requirement as needed.

10 High

NEC 240.21(C) ‐ Transformer Secondary

Conductors. Overcurrent protection on secondary side of transformer is greater than 25 feet.

X1BN

X2BNA

Verify cable lengths. Install appropriately sized overcurrent protection within 25 feet of the transformer secondary as needed.

11 High Inadequately rated equipment

PNL 1HM

PNL 1H

PNL MPPAE

PNL MPPBE

Reevaluate with actual cable lengths. Study used SSOE study to obtain breaker information for these panels. Confirm breaker modeled in the study reflect actual breakers installed.

12 High Inadequately rated equipment PNL 1DCHA

Study used SSOE study to obtain breaker information for these panels. Confirm breaker modeled in the study reflect actual breakers installed.

If necessary replace TEY breakers with 22kA rated breakers

13 High Inadequately rated equipment PNL D1DEH

Study used SSOE study to obtain breaker information for these panels. Confirm breaker modeled in the study reflect actual breakers installed.

Replace breakers SGHA breakers with 50kA rated breakers

14 High Inadequately rated equipment PNL 1DLHA Replace breakers SEHA breakers with 35kA rated breakers

15 Medium Equipment evaluated based on SSOE study Multiple Equipment in Short

Circuit Table with Note 3 and 4.

Equipment information was obtained from SSOE study and

2015 study. Confirm equipment are modeled correctly to ensure adequacy.

16 Low Coordination ‐ General

Multiple breakers with recommended settings marked in RED in the settings table

Implement recommended settings to normal circuit breakers to improve coordination.

1.4 Study Highlights

1.4.1 Short-Circuit

Of the 115 device locations evaluated for adequacy to interrupt or withstand the maximum three-phase short-circuit current to which they could be subjected, 7 were identified to be INADEQUATE. The Short-Circuit Evaluation Table lists equipment that was not evaluated because the equipment’s rating could not be determined. Refer to the study recommendation table for corrective actions.

1.4.2 Coordination

Setting recommendations have been made for adjustable devices to ensure optimum selectivity, reduce arc flash, or protect equipment. Time-current coordination (TCC) graphs were used to perform the evaluation for the overcurrent devices. Overall, the results showed that acceptable levels of selectivity were achieved among devices in the system except as discussed in Study Recommendations section.

The essential electrical system for this health care facility does not meet the 0.1 second coordination requirement as specified by the latest edition of the NEC. Consult the Study Recommendations section for more information.

While the electrical system does not meet the selective coordination requirements as specified in the latest edition of the NEC, coordination has been optimized as far as practicable.

The breakers in the system should be set to the recommended levels found in the Overcurrent Device Setting Tables section.

Recommendations for equipment changes can result in equipment which is larger in ampacity and/or physical footprint, may require changes to other parts of the electrical design (e.g., cable and conduit sizing), and could also impact the architectural design.

1.4.3 Arc Flash

This analysis will be added upon receipt of the requested data in section 3.2 Missing Data.

2 INTRODUCTION

This report has the following components:

Studies were performed using nationally recognized electrical engineering analysis software.

The system short-circuit analysis evaluates the adequacy of the distribution equipment shown on the enclosed one-line diagrams to withstand or to interrupt the calculated maximum available short-circuit current at its location.

The overcurrent device time-current coordination analysis determines the suggested settings and, where appropriate, the ampere ratings and types for the electrical power system protective devices to achieve the desired system protection and electrical service continuity goals.

The arc flash analysis establishes the arc flash boundary around electrical equipment within which a worker exposed to an arcing fault would expect to receive 2nd degree burns if not adequately protected. The analysis also determines the incident energy levels at specific working distances from equipment, which can be used to select appropriate personal protective equipment (PPE) to be worn when working within the arc flash boundary.

This report supersedes and invalidates results from any prior study for the scope of equipment being reviewed.

Electrical system changes within the facility or in the utility system can have a significant impact on the results of this power system analysis, which is a “snapshot” of as-found system conditions. As such, it is recommended that this analysis be re-evaluated on a regular basis, not to exceed 5 years, to account for electrical system changes. NFPA 70B and 70E address the issue of equipment maintenance and failure to properly maintain equipment may invalidate these results

A “REFERENCES” section near the end of the report cites who supplied information or how the data was obtained. The majority of this data is filed with the project and has not been reproduced in this report. Abbreviations and trademarks referenced throughout this report are also listed in an appendix.

3 STUDY DATA

3.1 Importance

The results of the study analyses are highly dependent on the accuracy of study data.

Modifications or clarifications of study data will likely alter study results. This study recommends a re-evaluation with actual utility data and cable lengths.

Short-circuit calculations can be conservatively estimated in order to evaluate equipment short-circuit ratings. Overcurrent device coordination can be evaluated using estimated short-circuit values to determine how well the system coordinates. For the following study types, it is essential to have accurate and complete data because of the significant impact the data has on the arc flash results.

This study will be revised to include these analyses once all the required data has been obtained. See section 0 Missing Data for a full list of data needed.

3.2 Missing Data

The following pages list critical information that was not available:

Updated utility primary fault current and confirmation of utility transformer and fuse information

Cable sets (per phase), size (AWG), type (Cu/Al), and length for the cables shown on the following pages.

Existing breaker information as listed on the following pages. Please provide breaker catalog number, model, trip unit, and existing settings as applicable.

ATS submittal (including withstand rating) for the following ATSs:

o ATS-LS o ATS-EQE o ATS-FP (Fire Pump controller)

The system one-line diagram identifies equipment with missing data.

Typical One-line color codes Black = Verified/Complete Orange = Assumed/Estimated Red = Incomplete/Missing

MISSING FEEDER INFORMATION VA Medical Healthcare

1 El Paso, TX

POWER SYSTEM ENGINEERING 1 Q2C: 50753956

Cable ID From To Cable Sets

(per phase) Size (AWG)

Type

(Cu/Al)

Length

(ft)

Cable100 3050 EDS ATS‐EQE

Cable101 1030 D4ANL 1034 4ANLD

Cable103 1030 D4ANL 1033 4ANLC

Cable104 1800 D1DNH 1810 1DNHA

Cable105 XPAE 2925 PAELA

Cable106 1030 D4ANL 1032 4ANLB

Cable107 1030 D4ANL 1031 4ANLA

Cable109 1055 D3ANL 1056 3ANLA

Cable110 1800 D1DNH 1850 1DNHB

Cable111 1055 D3ANL 1057 3ANLB

Cable112 1055 D3ANL 1058 3ANLC

Cable113 1055 D3ANL 1059 3ANLD

Cable114 1055 D3ANL 1060 3ANLE

Cable115 2920 MPPAE S‐1

Cable116 1055 D3ANL 1061 3ANLF

Cable117 2920 MPPAE S‐2

Cable118 1000 MSA 1100 1HM

Cable119 1000 MSA 1110 1H

Cable120 XPBE 2931 PBELA

Cable122 2930 MPPBE XPBE

Cable123 1500 MSB 1700 MTCE ENERG FAC

Cable125 1500 MSB 1750 MRI

Cable126 1810 1DNHA X1DNA

Cable127 1500 MSB 1800 D1DNH

Cable128 2930 MPPBE ELEV T‐1

Cable129 2910 D1DEH 2920 MPPAE

Cable130 2930 MPPBE ELEV T‐2

Cable131 2910 D1DEH 2930 MPPBE

Cable133 2910 D1DEH X1DNC

Cable134 2940 D1DNL 2941 1BLNB

Cable135 X1DNC 2940 D1DNL

Cable136 X1DNA 1820 1DNLA

Cable137 2920 MPPAE ELEV P‐1

Cable138 2940 D1DNL 2942 1BLNC

Cable139 2920 MPPAE ELEV P‐2

Cable141 1820 1DNLA 1830 1DNLB

Cable143 1580 2BNLA 1581 2BNLB

Cable145 1580 2BNLA 1582 2BNLC

Cable147 2205 1DCHA 2206 2HC

Cable149 2205 1DCHA X1DC

Cable151 X1DC 2207 1DCLA

Cable155 2245 SC 4TH FL BP 2250 4ACHA

Cable157 2245 SC 4TH FL BP X4AC

Cable159 X4AC 2255 4ACLA

Cable165 X2BC 2635 2BCLA

Cable166 2630 2BCHA X2BC

Cable167 2625 NC 2ND FL BP 2630 2BCHA

MISSING FEEDER INFORMATION VA Medical Healthcare

1 El Paso, TX

POWER SYSTEM ENGINEERING 1 Q2C: 50753956

Cable ID From To Cable Sets

(per phase) Size (AWG)

Type

(Cu/Al)

Length

(ft)

Cable169 X3BC 2646 3BCLA

Cable170 2645 3BCHA X3BC

Cable171 2640 NC 3RD FL BP 2645 3BCHA

Cable175 2650 NC 4TH FL BP 2651 4BCHA

Cable98 1020 D2ANH 1086 4ANHA

Cable99 2920 MPPAE XPAE

Q2C: 50753956

POWER SYSTEM ENGINEERING

Item # Equipment Name Breaker Name Breaker Catalog Number, Model, Trip Unit, and Settings (if applicable)

1 1000 MSA 1000-10 CH3 FDR*

2 1000 MSA 1000-11 1HM FDR*

3 1000 MSA 1000-12 1H FDR*

4 1110 1H 1110-00 1H MAIN*

5 1110 1H 1100-01 1HM LGST*

6 3050 EDS 3050-06 ATS-EQ5 FDR*

7 3050 EDS 3050-10 ATS-EQE FDR*

8 2910 D1DEH 2910-01 MPPAE FDR*

9 2910 D1DEH 2910-02 MPPBE FDR*

10 2940 D1DNL 2940 D1DNL MAIN*

11 2205 1DCHA 2205 1DCHA MAIN*

12 2205 1DCHA 2205-03 SC BUS FDR*

13 2205 1DCHA 2205-02 2HC FDR*

14 2207 1DCLA 2207-00 1DCLA MAIN*

15 2910 D1DEH 2910-03 X1DNC FDR*

16 1500 MSB 1500-06 MTCE ENERG FDR*

17 1500 MSB 1500-07 MRI FDR*

18 1500 MSB 1500-08 D1DNH FDR*

19 1800 D1DNH 1800-01 1DNHA FDR*

20 1810 1DNHA 1810-01 X1DNA FDR*

21 1800 D1DNH 1800-01 1DNHB FDR*

22 1580 2BNLA 1580-00 2BNLA MAIN*

23 2215 SC 2ND FL BP 2215-01 2ACHA FDR*

24 2230 SC 3RD FL BP 2230-01 3ACHA FDR*

25 2245 SC 4TH FL BP 2245-01 4ACHA FDR*

26 2245 SC 4TH FL BP 2245-02 X4AC FDR*

27 2610 NC 1ST FL BP 2610-01 1BCHA FDR*

28 2625 NC 2ND FL BP 2625-01 2BCHA FDR*

29 2640 NC 3RD FL BP 2640-01 3BCHA FDR*

30 2650 NC 4TH FL BP 2650-01 4BCHA FDR*

31 2650 NC 4TH FL BP 2650-02 X4BC FDR*

32 1055 D3ANL 1055-01 3ANLA FDR*

33 1055 D3ANL 1055-02 3ANLB FDR*

34 1055 D3ANL 1055-03 3ANLC FDR*

35 1055 D3ANL 1055-04 3ANLD FDR*

36 1055 D3ANL 1055-05 3ANLE FDR*

37 1055 D3ANL 1055-06 3ANLF FDR*

38 1100 1HM 1100 1HM LGST*

39 1100 1HM 1100-00 1HM MAIN*

40 1110 1H 1100-02 1HM LGST*

41 1010 D3XHA 1010-01 D3XHA LGST*

42 2920 MPPAE 2920-00 MPPAE MAIN*

43 2930 MPPBE 2930-00 MPPBE MAIN*

44 2940 D1DNL 2940-01 1BNLC*

45 2920 MPPAE 2920-01 ELEV P-1 FDR*

46 2920 MPPAE 2920-02 ELEV P-2 FDR*

47 2920 MPPAE 2920-05 XPAE FDR*

48 2925 PAELA 2925 PAELA MAIN*

49 2920 MPPAE 2920-03 S-1 FDR*

50 2920 MPPAE 2920-04 S-2 FDR*

51 2930 MPPBE 2930-01 XPBE FDR*

52 2931 PBELA 2931 PBELA MAIN*

53 2930 MPPBE 2930-02 ELEV T-1 FDR*

54 2930 MPPBE 2930-03 ELEV T-2 FDR*

MISSING BREAKER INFORMATION

Q2C: 50753956

POWER SYSTEM ENGINEERING

Item # Equipment Name Breaker Name Breaker Catalog Number, Model, Trip Unit, and Settings (if applicable)

MISSING BREAKER INFORMATION

55 2940 D1DNL 2940-01 1BNLB FDR*

56 2206 2HC 2206-00 2HC MAIN*

57 2205 1DCHA 2205-01 X1DC FDR*

58 1595 1BNLA 1595-00 1BNLA MAIN*

59 1820 1DNLA 1820-00 1DNLA MAIN*

60 1820 1DNLA 1820-01 1DNLB FDR*

61 1830 1DNLB 1830-00 1DNLB MAIN*

62 1580 2BNLA 1580-01 2BNLB FDR*

63 1580 2BNLA 1580-02 2BNLC FDR*

64 2255 4ACLA 2255-00 4ACLA MAIN*

65 2635 2BCLA 2635-00 2BCLA MAIN*

66 2630 2BCHA 2630-01 X2BC FDR*

67 2646 3BCLA 2646-00 3BCLA MAIN*

68 2645 3BCHA 2645-01 X3BC FDR*

69 3300 GPS 3300-01 EDS FDR*

3.3 Estimates & Assumptions

Some assumptions, or estimates, were required and may affect the results of this study.

In general, assumptions, or estimates, are needed because of limited access, safety concerns in obtaining equipment nameplate data, or lack of documentation. Significant differences between the assumptions, or estimates, listed here and actual values will require that this power system analysis be revised.

The following assumptions, or estimates, were made for the reasons given above:

1. Motor loads located at MSA and MSB were estimated to be 30% of the main breaker rating.

2. Where conductor lengths were not available, a length of 9 feet was used.

3. Where conductor sizes could not be determined, cables sized per NEC Edition table 310.15(B)(16) were used in the analysis. These estimates are noted on the one-line diagrams.

4. Equivalent ampacity Square D busway impedance values were used for busway runs where exact impedance data is unknown.

5. For low-voltage circuit breakers where the adjustable setting(s) was undeterminable, the recommended setting(s) was used.

4 SHORT-CIRCUIT ANALYSIS

4.1 General Procedure

An electrical system short-circuit analysis is used for the following:

1) To compare the calculated maximum fault current with the interrupting ratings of overcurrent protective devices such as fuses and circuit breakers.

2) To investigate applicable short-circuit series ratings and the protection of electrical equipment by current-limiting devices.

3) To verify the adequacy of other equipment, such as switches and equipment bussing, to withstand the effects of the calculated maximum fault current levels.

4) To assist in the selection and/or determination of settings for relays, fuses and circuit breakers.

5) To provide input (along with device trip characteristics) to an arc flash hazard analysis.

This analysis calculates maximum available three-phase, RMS symmetrical, short-circuit amperes at each piece of equipment in the system. The calculation procedures are based on recommendations included in ANSI/IEEE/IEC standards: 399 (Brown Book), 551 (Violet Book), 62271-37-013 (supersedes C37.013), C37.04, C37.13, & C37.010.

The modeling software simulates a bolted three-phase fault at each point of consideration in the system and calculates the maximum available short-circuit current at that point without any reduction due to current-limiting overcurrent devices which may be present. (However, the effects of current-limiting devices are considered when determining the adequacy of the equipment.) The calculated short-circuit values are RMS symmetrical amperes and are comparable with the RMS symmetrical short-circuit ratings of electrical equipment.

Electrical distribution equipment must be able to withstand and/or interrupt the most severe fault duty that it may be subjected to at its location in the system. In particular, NEC Section 110.9 requires circuit breakers to have a rating sufficient for interrupting the maximum available fault current present at their line side terminals. For locations where calculated fault currents exceed the ratings of the equipment, recommendations for corrective actions are provided.

Equipment short-circuit withstand and interrupting ratings are expressed in symmetrical RMS current. However, fault currents are not purely symmetrical in practice, as system inductance introduces a degree of asymmetry for at least the first few cycles of a fault.

The magnitude and duration of this asymmetrical component depends on several factors, including characteristics of system components (conductors, transformers, and loads) and the exact point on the current waveform that the fault begins—the level of asymmetry even differs from phase to phase in a three-phase system. Because of the uncertainty in asymmetry for a given fault event, the capability of devices to interrupt asymmetrical fault current is based on the maximum possible asymmetrical fault current level at the point of application. The more inductive the circuit, as measured by the calculated system X/R ratio, the more asymmetrical the fault current can be. If the calculated X/R level exceeds a certain level, then the increased asymmetrical duty must be taken into account when breaker ratings are assessed.

Low-voltage circuit breakers and fuses are tested to establish their interrupting ratings based on a circuit with a fixed X/R ratio, as defined in the various product standards (UL and ANSI). For example, an ANSI low-voltage power circuit breaker is tested in a circuit with an X/R ratio of 6.591. If such a breaker is applied at a system bus with a calculated X/R ratio of 6.591 or less and the calculated RMS symmetrical fault current is within the symmetrical interrupting rating of the breaker, then it is assumed that the breaker is also able to interrupt and withstand the asymmetrical current resulting from a fault at that location. If a low voltage breaker is applied at a location with an X/R ratio greater than that of the design test circuit, the calculated fault current must be multiplied by an adjustment factor that accounts for this. This resultant “fault duty,” which is greater than the calculated fault current, is then compared to the breaker’s interrupting rating in order to determine if the breaker is adequately rated. Different classes of low-voltage breakers have different test X/R values, and each type has its own set of multiplication factors. Design test circuit power factors and associated X/R ratios are as shown in Table 1. The low-voltage short-circuit output report shows the calculated fault duty levels calculated at each bus, and when these values differ from the calculated short-circuit current levels, they are used in the device evaluation tables. See IEEE 1015-1997, IEEE Recommended Practice for Applying Low-Voltage Circuit Breakers Used in Industrial and Commercial Power Systems, for additional details.

Table 1: Summary of Test Power Factor and X/R Values for LV Devices.

Device pf X/R Ratio Power circuit breaker, unfused 0.15 6.591

Power circuit breaker, fused 0.20 4.899 Molded case breaker, interrupting rating greater than 20000 A 0.15-0.20 6.591-4.899

Molded case breaker, interrupting rating 10001 to 20000 A 0.25-0.30 3.9-3.18

Molded case breaker, interrupting rating 10000 A and less 0.45-0.50 2.0-1.732

For power circuit breakers, the power factors are taken from ANSI/IEEE C37.13. For molded case breakers, the power factors are taken from NEMA standard AB1. Since the NEMA standard specifies a range of test circuit power factors, the highest value (lowest X/R ratio) is used to determine the multiplying factor. This produces the most conservative (largest) factor.

For equipment supplied from more than one source, there is no industry standard that defines hard requirements for whether the equipment must be rated for the short-circuit contribution from all sources. The National Electrical Code requires that “consideration shall be given to the contribution of fault currents from all interconnected power sources for the interrupting and short-circuit current ratings of equipment on interactive systems”. This does not require full rating to the sum of source short-circuit contributions, but rather consideration of the specific application. It is common industry practice to allow equipment which parallels sources for only very short windows of time – typically during closed-transition load transfers between sources – to have short-circuit/interrupting ratings suitable for the short-circuit contribution from the single source with the highest available fault current. The paralleling time may be limited to a specific value, such as 100ms, by the serving utility, or may otherwise be undefined but presumed to have no intentional paralleling delay and thus be approximately 100ms, or less. The value of 100ms is also mentioned in IEEE 1547-2018 as a paralleling time below which that standard does not apply to other than application with utility network systems.

In this analysis, equipment supplied by multiple sources where there is a reasonable expectation of “no intentional paralleling delay”, the highest single-source fault duty is given as the basis of adequacy of short-circuit withstand/interrupting ratings. This is not intended to construe that all risks due to faults in different locations relative to the equipment during a paralleled condition have been evaluated, but rather as a tool to allow the system designer to perform such evaluation. It is advised that a means of limiting the paralleling time to approximately 100ms, outside of an automation controller, PLC, or similar device, be considered in the over-all mitigation of risk.

Further, this is not intended to construe that all utility restrictions on paralleling time have been met; such considerations are within the purview of the system designer and beyond the scope of this study.

For equipment supplied by multiple sources where there is not a reasonable expectation of “no intentional paralleling delay”, such as sources that are intentionally paralleled continuously or for a finite period of time for soft load transfers, the full short-circuit contribution from all sources of supply is used as the basis for adequacy of short-circuit withstand/interrupting ratings.

The included one-line diagrams are a simplified version of the system drawings, showing only those parts of the electrical system under consideration. The various circuit locations on the diagrams have been labeled with bus identification numbers so input data could be supplied to the computer and the computer output could be readily interpreted.

4.2 Data Used in the Calculations

4.2.1 Power Company Data

Rio Grande Electric Coop has advised that the maximum available three-phase short-circuit current is 41.193kA at 480V. An X/R ratio of 8 was assumed for this fault current.

These values determined the starting point for the analysis. No minimum or alternate switching levels were given.

4.2.2 Generator Data

It has been determined that the 750kW generator has a subtransient reactance of 12.65% with an 80% PF and an estimated X/R ratio of 20 at 480V. The calculated maximum available bolted three-phase RMS symmetrical short-circuit current at the point of common coupling to the system (i.e. ATS) is considerably higher from the normal source compared to the generator source. The "Short Circuit Evaluation Table" is based on the higher source calculations. Therefore, all equipment determined to be adequate under normal utility supply conditions will also be adequate when the generator is in operation.

4.2.3 Cable Data

The conductor (cable and/or busway) data used for each circuit segment are shown in the SHORT CIRCUIT INPUT/OUTPUT DATA appendix. Included are lengths, number per phase, size, conductor material, cable insulation type, conduit material and resistance and reactance values. Also, conductor lengths, number per phase, and size and conductor material are recorded on the one-line diagrams.

Resistance values are based on 25 degrees Celsius (room temperature) rather than the full load temperature usually shown in descriptive literature because short-circuits can occur when the circuit is initially energized or lightly loaded as well as when fully loaded.

4.2.4 Transformer Data

Nameplate transformer percent impedance and typical X/R ratio values were used for all transformers. The exact R and X component values used are shown in the SHORT CIRCUIT INPUT/OUTPUT DATA appendix.

4.2.5 Motor Contribution to Short-Circuit Current

Motor contribution to the short-circuit current is taken into account in this short-circuit analysis. During the first few cycles of a fault, running motors act as generators and produce a current which will combine with the source short-circuit current flowing to the fault as illustrated in Figure 1. Sources may be, but are not limited to, the Power Company, local generators, or both.

Figure 1: Example motor contribution.

Connected motors shown on the study one-line were assumed to be running at the time of the fault. Motors fed by adjustable speed drives equipped with bypass contactors were considered to contribute to system fault currents as well. However, motors fed by drives without bypass contactors were not considered since they do not contribute to fault current. Redundant motors shown on the study one-line were also assumed to be running at the time of the fault unless operating controls prohibit these conditions.

A motor’s contribution to a fault at its terminals is equal to the full-load ampere (FLA) rating of the motor divided by its per-unit subtransient reactance, similar to the contribution from a generator. However, at the upstream switchboard, panelboard, or motor-control center, the fault contribution from the individual motors is reduced by the impedance of the motor branch circuit conductors. Since data on motor subtransient reactance and branch-circuit conductor lengths is often difficult to obtain, assumptions regarding the motors’ subtransient reactance are typically made when the system model is built.

For calculation of low-voltage fault duty, the contribution from induction motors and synchronous motors in the system are considered. For small induction motors (less than 50 hp) where the impedance of the installation (i.e., motor and conductor) is not known, a fault contribution of approximately 4 times rated current, is estimated. Larger motors (50 hp and above) have an estimated fault contribution of approximately 5 times rated current. This is consistent with recommendations in IEEE Std. 141, IEEE Recommended Practice for Electric Power Distribution for Industrial Plants (the IEEE Red Book).

If applicable, multiplying factors are adjusted per Table 7 of ANSI/IEEE C37.010, IEEE Application Guide for AC High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis for medium/high voltage fault duty. The table also shows contributions from induction motors less than 50 hp to be neglected.

The motor short-circuit contribution is determined and included in the computer short-circuit analysis so that the results should represent the highest short-circuit current to which the equipment might be subjected.

Unless otherwise indicated in the SC Computer Input Tabulations appendix, some motor loads are modeled as lumped induction motors connected directly to the low voltage buses using the recommended subtransient reactance values from C37.010, C37.13, and IEEE Std. 141. These modeled values appear in the appendices.

4.3 Short-Circuit Analysis Results

After making the calculations, the distribution equipment was checked to determine its adequacy to interrupt or withstand the effects of the calculated maximum short-circuit current at its location. For some solidly-grounded systems, like close-coupled unit substations and generator gear, it is possible the bolted three-phase fault current is not the maximum fault current. When applicable, the bolted line-to-ground fault current was considered instead. The results are listed in the "SHORT-CIRCUIT EVALUATION

TABLE".

Listed in the tables are the calculated short-circuit currents at each piece of equipment and the ratings of the lowest rated device in the equipment enclosure. Comparing the two sets of values shows that all of the equipment examined is either adequate by itself or when used in series with another circuit breaker or protected by a line side current-limiting fuse or circuit breaker except for the equipment discussed in the Study Recommendations section.

The short-circuit evaluation table shows buses with #N/A in the “NOTES” column. This is defined at the bottom of the table as #N/A = Number not available. Some of these buses do not require evaluation and may correspond to equipment such as transformer windings or motor terminals.

The table also lists some equipment that was not evaluated because the equipment’s rating could not be determined at the time of study preparation. These are identified by Note #1 in the far right hand column of the table. Evaluation of this equipment by the customer is necessary to verify the equipment’s short-circuit current rating is greater than the calculated fault duty, which can be evaluated by referring to the short-circuit output report. For each bus modeled, that report contains evaluations for UL and ANSI equipment and if necessary, Power System Engineering can assist in this evaluation.

For equipment evaluation, if a low voltage breaker is applied at a location with an X/R ratio greater than that of the design test circuit, the calculated fault current must be multiplied by an adjustment factor found in industry standards.

Refer to the Summary of Test Power Factor and X/R Values for LV Devices table in the General Procedure section for more information.

NEC 110.9 requires equipment to have a rating sufficient for interrupting the maximum available fault current present at the line side terminals of the equipment. NFPA 70E Article 210 also requires electrical equipment to have appropriate ratings to withstand or interrupt the available fault current. Where calculated available fault currents exceed the ratings of the equipment, remedial action, possibly including upgrade or replacement of the affected equipment, is required to comply with the NEC, NFPA 70E, and OSHA regulations. A risk of equipment damage, property damage, and personal injury exists when equipment has either inadequate withstand ratings or contains overcurrent protective devices (OCPDs) with inadequate interrupting ratings.

Equipment with inadequate ratings in this category can suffer damage which may include bent busbars, melted contactors, ruptured enclosures, or OCPDs may not be able to interrupt faults (three-phase bolted or arcing) properly.

Input data and short-circuit output data are included in the appendices.

4.4 Short-Circuit Evaluation Table

El Paso, TX

POWER SYSTEM ENGINEERING Q2C: 50753956

EQUIP. DESCRIPTION LOWEST RATED DEVICE MAXIMUM LINE SIDE LINE SIDE

BUS PER SYSTEM ONE NOMINAL IN EQUIPMENT ENCLOSURE AVAILABLE X/R MAXIMUM SERIES NOTES

1000 MSA 480 #N/A 46270.49 7.3181 #N/A

1000 MSA 480 PJ 65,000 50,039 7.32 Adequate

1005 MC1DN 480 LJ 65,000 43,032 5.51 Adequate

1006 MP2AN 480 BD/SQD 18,000 13,740 1.22 Adequate

1007 MP3AN 480 EDB 18,000 11,458 1.17 Adequate

1008 MP4AN 480 EDB 18,000 9,824 1.14 Adequate

1010 D3XHA 480 THFK 25,000 15,149 2.13 Adequate 4

1020 D2ANH 480 BG/SQD 35,000 12,906 1.58 Adequate

1025 X4AN ECB 480 JG 35,000 10,998 1.47 Adequate

1030 D4ANL 208 BD/SQD 25,000 6,768 1.60 Adequate

1031 4ANLA 208 SCCR10 10,000 6,376 1.46 Adequate 5

1032 4ANLB 208 SCCR10 10,000 6,376 1.46 Adequate 5

1033 4ANLC 208 SCCR10 10,000 6,376 1.46 Adequate 5

1034 4ANLD 208 SCCR10 10,000 6,376 1.46 Adequate 5

1040 4ANLE 208 QOB‐VH 22,000 5,274 1.17 Adequate 5

1050 X3AN ECB 480 JG 35,000 11,733 1.51 Adequate

1055 D3ANL 208 THQD 22,000 6,683 2.55 Adequate

1056 3ANLA 208 SCCR10 10,000 6,783 2.22 Adequate 5

1057 3ANLB 208 SCCR10 10,000 6,783 2.22 Adequate 5

1058 3ANLC 208 SCCR10 10,000 6,783 2.22 Adequate 5

1059 3ANLD 208 SCCR10 10,000 6,783 2.22 Adequate 5

1060 3ANLE 208 SCCR10 10,000 6,783 2.22 Adequate 5

1061 3ANLF 208 SCCR10 10,000 6,783 2.22 Adequate 5

1062 3ANLG 208 QOB‐VH 22,000 5,648 1.74 Adequate

1065 D2ANL 208 QD 25,000 6,858 1.39 Adequate

1070 2ANLF 208 QOB‐VH 22,000 4,728 0.96 Adequate

1080 2ANHA 480 #N/A 10,467 1.21 #N/A 1

1085 3ANHA 480 SCCR10 10,000 9,746 1.13 Adequate 5

1086 4ANHA 480 #N/A 12,282 1.47 #N/A 1

1090 CH3 480 #N/A 36,315 5.28 #N/A 1

1100 1HM 480 TEY(3P) 14,000 48,017 5.25 INADEQUATE 4, 6

1110 1H 480 TED(3P) 18,000 51,566 6.08 INADEQUATE 4, 6

1110 1H 480 SFH(3P) 35,000 46,354 6.08 INADEQUATE 4, 6

1110 1H 480 SGH4 35,000 46,354 6.08 INADEQUATE 4, 6

1500 MSB 480 LJ 65,000 49,496 6.99 Adequate 1

1505 CH2 480 #N/A 34,256 5.34 #N/A 1

SHORT‐CIRCUIT

EVALUATION TABLE

#N/A = Number not available.

ETAP SCET Page 1 of 5

[Template Ver. 14.8] #Internal

El Paso, TX

POWER SYSTEM ENGINEERING Q2C: 50753956

EQUIP. DESCRIPTION LOWEST RATED DEVICE MAXIMUM LINE SIDE LINE SIDE

BUS PER SYSTEM ONE NOMINAL IN EQUIPMENT ENCLOSURE AVAILABLE X/R MAXIMUM SERIES NOTES

1000 MSA 480 #N/A 46270.49 7.3181 #N/A

SHORT‐CIRCUIT

EVALUATION TABLE

1510 D1BNH 480 LH 35,000 18,667 1.40 Adequate

1515 X3BN ECB 480 LG 35,000 14,336 1.16 Adequate

1520 D3BNL 208 BD/SQD 25,000 8,007 2.01 Adequate

1525 3BNLE 208 QOB‐VH 22,000 6,067 1.31 Adequate

1530 X4BN ECB 480 JG 35,000 12,874 1.24 Adequate

1540 4BNLA 208 QOB‐VH 22,000 7,156 1.55 Adequate

1545 4BNLB 208 SCCR10 10,000 6,489 1.36 Adequate 5

1550 4BNLC 208 SCCR10 10,000 5,844 1.20 Adequate 5

1570 X2BNA ECB 480 JG 35,000 13,310 1.18 Adequate

1575 2BNLD 208 QOB‐VH 22,000 6,462 1.23 Adequate

1580 2BNLA 208 THQD 22,000 5,818 1.18 Adequate

1581 2BNLB 208 SCCR10 10,000 5,503 1.11 Adequate 5

1582 2BNLC 208 SCCR10 10,000 5,503 1.11 Adequate 5

1585 X2BNB ECB 480 JG 35,000 12,802 1.16 Adequate

1590 1BNLD 208 QOB‐VH 22,000 3,510 1.57 Adequate

1595 1BNLA 208 THQD 22,000 3,179 1.41 Adequate

1600 1BNHA 480 #N/A 15,015 1.10 #N/A 1

1610 2BNHA 480 #N/A 10,676 0.85 #N/A 1

1700 MTCE ENERG FAC 480 #N/A 42,382 5.10 #N/A 1

1750 MRI 480 #N/A 42,842 5.96 #N/A 1

1800 D1DNH 480 SEL(3P) 65,000 46,500 6.18 Adequate 4

1810 1DNHA 480 SEL(3P) 65,000 39,944 3.50 Adequate 4

1820 1DNLA 208 THQB 10,000 2,608 1.65 Adequate

1830 1DNLB 208 THQB 10,000 2,540 1.57 Adequate

1850 1DNHB 480 #N/A 33,646 1.44 #N/A 1

2000 ATS‐EQ3(E) 480 SCCR35 35,000 14,008 4.26 Adequate 2

2000 ATS‐EQ3(N) 480 SCCR35 35,000 33,385 2.75 Adequate 2

2005 MP1CC 480 LD 18,000 14,633 1.26 Adequate

2010 MP2CC 480 EDB 18,000 12,271 1.20 Adequate

2015 MP3CC 480 EDB 18,000 10,712 1.17 Adequate

2020 MP4CC 480 EDB 18,000 7,186 0.74 Adequate

2100 ATS‐EQ4(E) 480 SCCR50 50,000 15,740 5.96 Adequate

2100 ATS‐EQ4(N) 480 SCCR50 50,000 36,045 3.20 Adequate

2110 CH1 480 #N/A 27,532 2.50 #N/A 1

2200 ATS‐CR1(E) 480 SCCR42 42,000 14,030 4.81 Adequate 3

#N/A = Number not available.

ETAP SCET Page 2 of 5

El Paso, TX

POWER SYSTEM ENGINEERING Q2C: 50753956

EQUIP. DESCRIPTION LOWEST RATED DEVICE MAXIMUM LINE SIDE LINE SIDE

BUS PER SYSTEM ONE NOMINAL IN EQUIPMENT ENCLOSURE AVAILABLE X/R MAXIMUM SERIES NOTES

1000 MSA 480 #N/A 46270.49 7.3181 #N/A

SHORT‐CIRCUIT

EVALUATION TABLE

2200 ATS‐CR1(N) 480 SCCR42 42,000 28,158 2.26 Adequate 3

2205 1DCHA 480 SFL(3P) 65,000 24,616 1.79 Adequate 4

2205 1DCHA 480 SEL(3P) 65,000 24,616 1.79 Adequate 4

2205 1DCHA 480 SGH4 35,000 24,616 1.79 Adequate 4

2205 1DCHA 480 TEY(3P) 14,000 24,616 1.79 INADEQUATE 4

2206 2HC 480 SEL(3P) 65,000 21,786 1.40 Adequate 4

2207 1DCLA 208 SEL(3P) 100,000 1,604 1.59 Adequate

2210 SOUTH CRITICAL BUS 480 SCCR10 10,000 7,686 1.31 Adequate

2215 SC 2ND FL BP 480 SED(3P) 18,000 7,331 1.29 Adequate

2220 2ACHA 480 TEY(3P) 14,000 6,642 1.14 Adequate

2225 2ACLA 208 QOB‐VH 22,000 1,396 1.55 Adequate

2230 SC 3RD FL BP 480 SED(3P) 18,000 7,007 1.27 Adequate

2235 3ACHA 480 TEY(3P) 14,000 6,787 1.22 Adequate

2240 3ACLA 208 QOB‐VH 22,000 1,397 1.56 Adequate

2245 SC 4TH FL BP 480 SED(3P) 18,000 6,710 1.25 Adequate

2250 4ACHA 480 SCCR10 10,000 6,459 1.18 Adequate

2255 4ACLA 208 SCCR10 10,000 2,290 1.56 Adequate

2300 ATS‐LS(E) 480 #N/A 14,471 5.39 #N/A

2300 ATS‐LS(N) 480 #N/A 33,654 2.86 #N/A

2305 1DLHA 480 SEH(3P)‐GE 25,000 29,719 2.31 INADEQUATE

2305 1DLHA 480 SFH(3P) 35,000 29,719 2.31 Adequate 4

2320 3ELHA 480 EGB 35,000 2,934 0.51 Adequate

2400 ATS‐EQ1(E) 480 SCCR42 42,000 15,208 5.76 Adequate 3

2400 ATS‐EQ1(N) 480 SCCR42 42,000 29,163 2.35 Adequate 3

2405 MP1DE 480 SGH4 35,000 19,662 1.68 Adequate 4

2410 MP1CE 480 EDB 18,000 13,560 1.07 Adequate

2500 ATS‐EQ2(E) 480 SCCR50 50,000 17,673 10.26 Adequate 3

2500 ATS‐EQ2(N) 480 SCCR50 50,000 41,059 4.65 Adequate 3

2510 D1DQH 480 SGH4 35,000 39,717 4.28 INADEQUATE 4

2510 D1DQH 480 SKH12 50,000 39,717 4.28 Adequate 4

2515 MP4CE 480 EDB 18,000 12,583 1.17 Adequate

2520 MP2CE 480 EDB 18,000 9,068 1.24 Adequate

2600 ATS‐CR2(E) 480 SCCR42 42,000 14,363 5.08 Adequate 3

2600 ATS‐CR2(N) 480 SCCR42 42,000 32,503 2.69 Adequate 3

2605 NORTH CRITICAL BUS 480 #N/A 10,085 2.40 #N/A 1

#N/A = Number not available.

ETAP SCET Page 3 of 5

El Paso, TX

POWER SYSTEM ENGINEERING Q2C: 50753956

EQUIP. DESCRIPTION LOWEST RATED DEVICE MAXIMUM LINE SIDE LINE SIDE

BUS PER SYSTEM ONE NOMINAL IN EQUIPMENT ENCLOSURE AVAILABLE X/R MAXIMUM SERIES NOTES

1000 MSA 480 #N/A 46270.49 7.3181 #N/A

SHORT‐CIRCUIT

EVALUATION TABLE

2610 NC 1ST FL BP 480 SFH(3P) 35,000 9,524 2.24 Adequate

2615 1BCHA 480 TEY(3P) 14,000 9,182 2.06 Adequate

2620 1BCLA 208 QOB‐VH 22,000 1,299 1.03 Adequate

2625 NC 2ND FL BP 480 SED(3P) 18,000 9,017 2.11 Adequate

2630 2BCHA 480 TEY(3P) 14,000 8,645 1.88 Adequate

2635 2BCLA 208 THHQB 22,000 1,415 1.58 Adequate

2640 NC 3RD FL BP 480 SED(3P) 18,000 8,558 2.00 Adequate

2645 3BCHA 480 TEY(3P) 14,000 8,216 1.80 Adequate

2646 3BCLA 208 THHQB 22,000 1,415 1.60 Adequate

2650 NC 4TH FL BP 480 SFH(3P) 35,000 8,140 1.91 Adequate

2650 NC 4TH FL BP 480 SED(3P) 18,000 8,140 1.91 Adequate

2651 4BCHA 480 SCCR10 10,000 8,063 1.84 Adequate 5

2655 4BCLA 208 THQD 22,000 2,198 1.67 Adequate

2655 4BCLA 208 SFL(3P) 100,000 2,198 1.67 Adequate

2660 4BCLB 208 QOB‐VH 22,000 2,166 1.63 Adequate

2700 ATS‐EQ5(E) 480 SCCR35 35,000 14,363 4.68 Adequate 2

2700 ATS‐EQ5(N) 480 SCCR65 65,000 27,040 1.89 Adequate

2710 1DEHA 480 EGB 35,000 24,277 1.70 Adequate

2800 ATS‐FP(E) 480 #N/A 2,109 0.29 #N/A

2800 ATS‐FP(N) 480 #N/A 2,208 0.25 #N/A

2900 ATS‐EQE(E) 480 #N/A 16,026 10.99 #N/A

2900 ATS‐EQE(N) 480 #N/A 41,250 5.72 #N/A

2910 D1DEH 480 SGH4 35,000 41,699 5.58 INADEQUATE 4

2910 D1DEH 480 SKH8 50,000 41,699 5.58 Adequate

2920 MPPAE 480 TED(3P) 18,000 42,887 5.15 INADEQUATE 4, 6

2921 ELEV P‐1 480 #N/A 34,817 3.34 #N/A 1

2922 ELEV P‐2 480 #N/A 34,817 3.34 #N/A 1

2923 S‐1 480 #N/A 34,852 3.35 #N/A 1

2924 S‐2 480 #N/A 34,852 3.35 #N/A 1

2925 PAELA 208 THHQB 22,000 1,546 4.73 Adequate 4

2930 MPPBE 480 TED(3P) 18,000 43,605 4.96 INADEQUATE 4, 6

2930 MPPBE 480 TFJ(3P) 22,000 39,198 4.96 INADEQUATE 4, 6

2931 PBELA 208 THHQB 22,000 1,547 4.72 Adequate 4

2932 ELEV T‐1 480 #N/A 35,637 3.25 #N/A 1

2933 ELEV T‐2 480 #N/A 35,637 3.25 #N/A 1

#N/A = Number not available.

ETAP SCET Page 4 of 5

El Paso, TX

POWER SYSTEM ENGINEERING Q2C: 50753956

EQUIP. DESCRIPTION LOWEST RATED DEVICE MAXIMUM LINE SIDE LINE SIDE

BUS PER SYSTEM ONE NOMINAL IN EQUIPMENT ENCLOSURE AVAILABLE X/R MAXIMUM SERIES NOTES

1000 MSA 480 #N/A 46270.49 7.3181 #N/A

SHORT‐CIRCUIT

EVALUATION TABLE

2940 D1DNL 208 THHQB 22,000 6,736 3.46 Adequate

2940 D1DNL 208 SGD 65,000 6,736 3.46 Adequate

2941 1BLNB 208 SCCR10 10,000 7,068 2.58 Adequate 5

2942 1BLNC 208 SCCR10 10,000 7,738 3.24 Adequate 5

3000 GEN#1 480 PG 35,000 20,144 15.57 Adequate

3050 EDS 480 JJ 65,000 19,103 12.18 Adequate

3200 GEN#2 480 PG 35,000 20,144 15.57 Adequate

3300 GPS 480 #N/A 16,885 13.70 #N/A 1

1 Check the interrupting ratings against maximum available fault current.

2 Evaluation based on time based rating.

3 Evaluation based on 34801189 study completed on Feb 2015. It is possible that the modeled device is not the lowest rated device in the equipment.

4 Evaluation based on devices modeled in the SSOE study provided in 2015. It is possible that the modeled device is not the lowest rated device in the equipment.

5 Evaluation based on the industry standard minimum rating for distribution panel and busway.

6 Re‐evaluated equipment with actual feeder lengths.

#N/A = Number not available.

ETAP SCET Page 5 of 5

5 OVERCURRENT DEVICE COORDINATION ANALYSIS

5.1 General Procedure

An overcurrent device time-current coordination analysis is an organized effort to determine the settings and, where appropriate, the ampere ratings and types for the over-current protective devices in an electrical system. The objective of the coordination analysis is to establish time-current coordination among the devices, thereby achieving the desired system protection and electrical service continuity goals.

Maximum protection requires that the overcurrent protective devices be rated, selected, and adjusted to allow the normal load currents to flow while instantaneously opening the circuit when abnormal currents flow.

However, maximum service continuity requires that the overcurrent protective devices be rated, selected, and adjusted so that only the overcurrent protective device nearest the fault opens and isolates the faulted circuit from the system, permitting the rest of the system to remain in operation. Protective devices farther from the fault location should therefore essentially act as backup protection for the devices nearer to the fault, allowing the fault to be cleared with a minimum of disruption to the system. This is referred to as “coordination” between the protective devices. This may allow longer duration faults when the fault point is nearer the service entrance; however, such faults are not as common, and setting the protective devices to operate in this manner is generally more desirable than deenergizing most or all of the system for a fault near one of the loads.

Selecting and setting the overcurrent devices is a procedure where the time-current characteristic curves of the various devices in series are compared with one another on a log-log graph. This procedure should take into account boundaries defined by load currents, short-circuit currents, and ANSI and NEC requirements.

Coordination usually will be obtained when the log-log plots of time-current characteristics show sufficient clear space or no overlap between the curves for the protective devices operating in series. Coordination will often stop short of complete selectivity when an acceptable compromise is reached between the various boundaries imposed on the selecting and setting procedure.

As shown on the one-line diagrams, each overcurrent protective device or motor under consideration by the program has been assigned an identification number so that the computer output could be readily interpreted.

5.2 Specific Procedure

5.2.1 Short-Circuit Current Considerations

All protective device characteristic curves shown on the time-current graphs end at the calculated maximum short-circuit current at that device.

5.2.2 Molded Case Breaker Coordination

A molded case circuit breaker will trip with no intentional time delay for short-circuit currents above its instantaneous trip setting. Because of this, molded case breakers in series can only be selectively coordinated with each other if there is sufficient impedance between them so that the maximum available…