Bowling 3 year info Part 2.pdf

Power System Engineering

June 2014

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 along with the proprietary methodologies and analysis tools of SEES. 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 Highlights

1.3.1 Short-Circuit Results

1.3.2 Coordination Results

1.3.3 Arc Flash Results

1.3.4 Other Results

2 INTRODUCTION

3 SYSTEM FINDINGS

3.1 Electrical System Description

3.2 Study Analysis

3.2.1 Short-Circuit

3.2.2 Coordination

3.2.3 Arc Flash

3.2.4 Other Results

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

4.2.6 Assumptions and Estimates

4.3 Short-Circuit Analysis Results and Recommendations

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 Time-Overcurrent Relay Coordination

5.2.4 Low-Voltage Ground-Fault Relay Settings

5.2.5 Transformer Protective Devices

5.2.6 Cable Protection

5.2.7 Selective Coordination and the National Electric Code

5.2.8 Assumptions and Estimates

5.3 Analysis of Results and Recommendations

5.3.1 NEC Compliance Issues and Other Issues

5.3.2 TCC Plot Remarks

5.4 Overcurrent Device Setting Table – AS FOUND Relay Settings

5.5 Overcurrent Device Setting Table – AS FOUND LV Breaker Settings

5.6 Time-Current Coordination Graphs – AS FOUND Settings

6 ARC FLASH HAZARD ANALYSIS

6.1 General Procedure

6.2 Specific Procedure

6.3 AF Hazard Analysis Results and Recommendations

6.3.1 Arc Flash Hazard Table Headings Guide and PPE Table

6.3.2 Arc Flash Hazard Analysis Table – AS-FOUND Settings

6.4 Power System Engineering Arc Flash Labeling Practice

6.4.1 Arc Flash Information Labels

6.4.2 General Safety Labels

APPENDIX A: ABBREVIATIONS AND TRADEMARKS

APPENDIX B: SHORT CIRCUIT INPUT TABULATIONS

APPENDIX C: SHORT CIRCUIT OUTPUT TABULATIONS

APPENDIX D: REFERENCES

APPENDIX E: SYSTEM STUDY ONE-LINE DIAGRAM

1 EXECUTIVE SUMMARY

1.1 Overview

This report documents the results of a Power System Engineering analysis for the Cooper Division of the Lexington VA Medical Center in Lexington, KY. 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. This study is intended to cover the Main, Tower, and Chiller buildings at the Lexington VAMC. Data collection for this project was performed at the site from January through March of 2014. Every effort is made to ensure that this power system study accurately represents the system as it exists at this time. Any changes made after these dates may not be reflected in this power system study.

The primary purpose of this power system study is to provide a short circuit, coordination, and arc flash analysis for the Lexington VAMC. The short circuit study evaluates the adequacy of the equipment to withstand the available fault current. The coordination study evaluates coordination between overcurrent protective devices as they are currently set. No specific settings recommendations are made in this power system study; however, general coordination issues are noted. The arc flash analysis evaluates the arc flash hazard for the equipment in the system based on the existing system configuration (breaker settings, generator setup, etc.) and the utility fault current as obtained during this data collection time frame.

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.

Revision #1 – June 17, 2014 This revision was initiated by Schneider Electric in order to correct issues in the study which were noticed during the process of affixing arc flash labels.

The working distance for switchgear ESB (032) in the tower building was changed to 24 in. The arc flash results are updated accordingly

It was observed in the field that the CATH LAB #2 (311) and CATH LAB #1

(312) busplugs were on the North Wing Riser (SBF) instead of the Emergency Riser (SBE). The model and study are updated accordingly to reflect this.

1.3 Study Highlights

1.3.1 Short-Circuit Results

Of the 383 device locations evaluated for adequacy to interrupt or withstand the maximum three-phase short-circuit current to which they could be subjected, forty one (41) 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 Analysis – Short Circuit section (Section 3.2.1) for a list of the equipment determined to be inadequate.

Inadequate

11%

Adequate 89%

Graph of equipment short-circuit capability

1.3.2 Coordination Results

This power system study considers only the AS-FOUND settings for this system. The Overcurrent Device Settings Tables in sections 5.4 and 5.5 document the settings used for this power system study to assess coordination and provide arc flash labels. No settings are recommended in this report.

Overall, the coordination study showed that acceptable levels of selectivity were not achieved among devices in the system. It is recommended that a comprehensive coordination study be performed in order to provide new settings for the overcurrent protective devices in this system.

1.3.3 Arc Flash Results

Four hundred and fifty three (453) locations were analyzed to determine the level of arc flash incident energy to which a worker might be exposed during an arc flash event. The majority of locations were determined to be category 0 (lowest). The highest category for which personal protective equipment may be used is category 4. It is not recommended work be performed live for equipment with the “Over 40 cal./cm2” designation (twenty-one (21) locations).

0 50 100 150 200 250 300

Cat 0

Cat 1

Cat 2

Cat 3

Cat 4

Over 40cal/cm2

Graph of arc flash hazard category occurrence

1.3.4 Other Results

Other issues, which are not formally in the scope of work, were observed in the course of data collection and analysis. These could be NEC compliance issues, equipment having poor condition of maintenance, or some other critical factor. Refer to the Study Analysis – Other Issues section (Section 3.2.4) for a list of issues noticed.

2 INTRODUCTION

This report has the following components:

Studies were performed using Power*Tools for Windows Software, version 7.0.2.5.

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 analyzes coordination as it currently exists in the system.

The flash hazard 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 SYSTEM FINDINGS

3.1 Electrical System Description

The facility at the Lexington VAMC is divided into three (3) distinct buildings. There is the main building, the tower building, and the chiller building. Power is provided to the system by KU at 12,470V to the main building. From here, the service entrance switchgear at 12,470V feeds the tower building, the chiller building, and the low voltage switchgear for the main building. For the chiller building, there are two (2) transformers which step the voltage down to 480V to serve the chiller building equipment. For the tower building, the main building MV gear feeds four (4) transformers which step the voltage down to 480V for distribution throughout the tower building.

The tower building transformers feed two (2) 3000A service busways, which subsequently feed the LV switchgear for the tower building.

There are two (2) different sets of generators for the Lexington VAMC. There is one (1) generator for the main building, and there are two (2) generators which feed paralleling switchgear for the tower building. The main building and tower building generation systems are entirely separate.

3.2 Study Analysis

Refer to each of the following sections for details. If issues are 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.

3.2.1 Short-Circuit

The results of the short-circuit analysis show that the equipment considered in the study is adequately rated for the projected fault current levels except for the following:

This section is intended to provide a list of the inadequate equipment; for bus ID numbers and device location on drawings refer to the complete Short Circuit Analysis Results and Recommendations section (Section 4.3)

Main Building Motor Control Center MCC4N Motor Control Center MCC3N Panel ELPGA Panel LP1C Panel LP2C Panel LP4C Panel LPGA Panel LPUH Panel LP1A Panel LP2A Panel LP3A Panel LP4A

Chiller Building Motor Control Center MCC#1

Tower Building Network Protectors for T1 and T4

SBD, SBE, SBC, SBH, SBA, SBB

NOTE: The ratings shown in the Short Circuit Evaluation table for this equipment represent the lowest rated breaker in the switchgear. This equipment could not be accessed in the field, and as such the ratings for the breakers were based on test reports which had been obtained prior to data collection. It is recommended that the equipment ratings for this equipment (switchgear bus bracing and breaker AIC rating) be verified.

Motor Control Center MCB Panel CLC Manual Transfer Switch for Panel CCU Panel CLA Panel CLG Panel HEMG Panel ELC

CATH LAB #1 DISC

Manual Transfer Switch for Panel ELE Panel LF Panel LE-1 Panel LE-2 Panel LG Primary Breaker for transformer T-PPP Panel LG – 6th Floor north Bus Plug for Panel L2 Panel LL

For more detailed information on this inadequate equipment, refer to the Short Circuit Analysis Results and Recommendations section (Section 4.3).

3.2.2 Coordination

This power system study considers only the AS-FOUND settings for this system. The Overcurrent Device Settings Tables in sections 5.4 and 5.5 document the settings used for this power system study to assess coordination and provide arc flash labels.

Overall, the coordination study showed that acceptable levels of selectivity were not achieved among devices in the system. It is recommended that a comprehensive coordination study be performed in order to provide new settings for the overcurrent protective devices in this system.

In some cases, it was observed that coordination issues could be remedied with different breaker settings. In other cases, the coordination issues would exist regardless of settings due the characteristics of the overcurrent protective device. A comprehensive coordination study can help determine the breakers where settings adjustment can improve coordination.

In addition to this, it is noted that many of the breakers in the tower building switchgear (SBA, SBB, SBC, SBD, SBE, and SBF) are equipped with older trip units without instantaneous functions (ie “LS” type breakers). It is recommended that these breakers be retrofitted with newer electronic LSI trip units. It is also recommended that the Siemens breakers in the main building low voltage switchgear (029) and the chiller low voltage switchgear (170) with the Static Trip II trip units be retrofitted with newer LSIG trip units.

Existing setting levels are provided in the Overcurrent Device Setting Tables section. These are the settings which are used to determine the arc flash hazard categories as shown in the Arc Flash Hazard Analysis Table in section 6.3.2.

It should be noted that if settings are changed for coordination concerns, it will be necessary to revisit the arc flash hazard analysis and determine if the hazard category has changed due to any breaker settings changes.

It is noted on the time current curves that some transformer inrush points are within the operating band of the primary breaker. Exact transformer inrush data could not be obtained for this job; as such, a default inrush value of 12.0 times the transformer primary FLA was assumed. This value may or may not be indicative of the actual transformer inrush value in the field for the transformer.

As this facility is currently in operation, it is recommended that transformer inrush issues be addressed on a case by case basis. If there is a circuit where nuisance tripping due to inrush is expected to be causing an issue, this circuit can be individually examined in more detail. It should be noted that more detailed information on the transformer will be required to facilitate this analysis.

3.2.3 Arc Flash

The results of the arc flash analysis show both the calculated arc flash incident energy (AFIE) and arc flash boundary distances at each bus under study.

Overly conservative available fault current values should not be used solely for an arc flash analysis. Therefore, multiple arc flash fault current scenarios were considered. These are described below.

Case #1 High Utility Source

Source Currents o KU Feed 136Q – 11,311 Amps at 12,470V (given fault current) o KU Feed 119P – 10,091 Amps at 12,470V (given fault current)

System Configuration o Normal operating conditions. For all switchgear with tie breakers, the ties were open and both mains were closed.

Case #2 Low Utility Source

Source Currents o KU Feed 136Q – 1,620 Amps at 12,470V (assumed low fault current) o KU Feed 119P – 1,620 Amps at 12,470V (assumed low fault current)

System Configuration o Normal operating conditions. For all switchgear with tie breakers, the ties were open and both mains were closed.

Case #3 High Utility Source

Source Currents o KU Feed 136Q – 11,311 Amps at 12,470V (given fault current)

System Configuration (refer to one line in Appendix E for breaker designations) o 003-01A closed (Main) o 003-01T closed (Tie) o 003-01B open (Main) o 039-001A closed (Main) o 039-001T closed (Tie) o 039-001B open (Main) o 170-01A closed (Main) o 170-01T closed (Tie) o 170-01B open (Main)

Case #4 Low Utility Source

Source Currents o KU Feed 136Q – 1,620 Amps at 12,470V (assumed low fault current)

System Configuration (refer to one line in Appendix E for breaker designations) o 003-01A closed (Main) o 003-01T closed (Tie) o 003-01B open (Main) o 039-001A closed (Main) o 039-001T closed (Tie) o 039-001B open (Main) o 170-01A closed (Main) o 170-01T closed (Tie) o 170-01B open (Main)

Case #5 Generator Source – “High”

Source Currents – Main Building o Generator Running Source Currents – Tower Building o Both (2) Generators Running

Case #6 Generator Source – “Low”

Source Currents – Tower Building o One (1) Generator Running

Case #7 Assumed Maximum Utility Source

Source Currents o KU Feed 136Q – 80,000 Amps at 12,470V (assumed fault current) o KU Feed 119P – 80,000 Amps at 12,470V (assumed fault current)

System Configuration o Normal operating conditions. For all switchgear with tie breakers, the ties were open and both mains were closed.

The results of all the scenarios were combined into one composite table showing the worst case results for each piece of equipment evaluated.

It is recognized that recommendations in this report may not be implemented simultaneously. It is customer’s responsibility to apply and update labels as recommendations are implemented or as conditions change.

There were twenty-one (21) locations where the arc flash incident energy level is greater than 40 cal/cm2 which is considered the upper limit defined by NFPA 70E. These are listed below

Main Building

MAIN BLDG LV SWG (039)

Chiller Building

CHILLER LV SWG (170)

Tower Building

FIRE PUMP NORM DISC (019)

FIRE PUMP ATS (033)

NETWORK PROTECTORS (200, 201, 202, 203)

MAIN SERVICE BUSWAYS (204, 205)

FIRE PUMP (206)

SBD, SBH, SBA, SBB, SBF, SBG (208, 211, 212, 213, 214, 215)

BUSPLUG CLR/CPR (352)

SBN-1 and SBN-2 DISC (356, 357)

This section is intended to provide a list of the dangerous equipment; for more information on these dangerous locations, and equipment location on drawings, refer to the Arc Flash Hazard Analysis Table in section 6.3.2 and the Arc Flash Hazard Analysis Results and Recommendations in section 6.3.

The arc flash hazard analysis and recommended PPE levels are no substitutes for safe work practices. As stated in NFPA 70E, burn injuries can occur even when adequate PPE is employed, and the recommended PPE may provide little or no protection against arc blast and its effects.

Protection from arc flash can best be provided by working only on circuits or equipment that have been placed in an electrically safe work condition. Work should not be performed on or near equipment listed “Dangerous” unless it has been placed in an electrically safe work condition.

3.2.4 Other Results

Other issues, which are not formally in the scope of work, were observed in the course of data collection and analysis. These could be NEC compliance issues, equipment having poor condition of maintenance, or some other critical factor. Refer to the NEC Compliance Issues and Other Issues section (Section 5.3.1) for more information on the potential NEC compliance issues.

This section is intended to provide a list of the potential issues; for bus ID numbers and device location on drawings refer to the complete NEC Compliance Issues and Other Issues section (Section 5.3.1).

Possible NEC violations follow:

NEC cable protection violations were noticed at the following locations; and either the pickup must be reduced or cable size must be increased.

Switchboard ESB3, Feeder to REMOTE RAD PANEL Busplug for LPUH, Feeder to LPUH SBC, Feeder to CPK SBC, Feeder to MCB Busplug for T-CPF, Feeder to T-CPF SBE, Feeder to HEMG1 SBE, Feeder to T-EPB Busplug for CATH LAB #2, Feeder to CATH LAB #2 SBA, Feeders to T-PCC and T-PFF SBA, Feeder to MCA SBA, Feeder to ATS-LS SBB, Feeder to SBJ SBB, Feeder to LE-1/PDD/PGG SBB, Feeder to T-SBK SBB, Feeder to T-PPP and T-SBL SBK, Feeder to PV-2 SBK, Feeder to PT

It should also be noted several cables appear to be in violation of NEC 240.21(C), which is commonly referred to as the tap rule. The following taps should be reviewed, and proper protection installed where necessary. It is assumed that there is overcurrent protection within the generator controls which protect the cables from the generators to the respective load side distribution equipment.

Feeder tap from secondary terminals of T-PKK, low-voltage transformer, to PKK Feeder tap from secondary terminals of T-CPL [PENTHOUSE], low-voltage transformer, to CPL [PENTHOUSE] Feeder tap from secondary terminals of T-PAA, low-voltage transformer, to PAA Feeder tap from secondary terminals of T-PY-2, low-voltage transformer, to PY-2, downstream panel

Apparent NEC Article 450 (primary protection) violations exist for the following transformers

75 KVA transformer which feeds CPH 45 KVA transformer which feeds CPF 30 KVA transformer which feeds EPB 30 KVA transformer which feeds EPC 45 KVA transformer which feeds PKK 45 KVA transformer which feeds PNN 45 KVA transformer which feeds PS

The following issues may or may not be NEC compliance issues, but were noticed during the data collection effort.

Room BU00 – This room on the ground floor of the tower building serves equipment both in and out of the room. There are wireways in this room which feed the equipment. The wireways are cluttered, and it is difficult to determine the sources and loads to and from the wireways. In addition to this, based on observations in the field it appears that some wireways in this room have multiple sources of power. This presents a safety hazard as it is more difficult to determine if the wireway is in an electrically safe work condition due to multiple sources of current. It is recommended that this room be completely reorganized and redone, with all wireways being removed and replaced with panelboards or other suitable equipment.

Panel LPE2 – It was observed that this panel is missing two (2) blanks.

Bus plug for panel PP1D – It was observed that this busplug does not have the required clearances.

Bus plug for panel EPP3D – It was observed that there are clearance issues for this bus plug due to the new conduit.

Panel PP3D SECT #1 – It was observed that this panel is missing one (1) blank.

Bus plug for panel LP3A – It was observed that the door for this bus plug is damaged.

Panel LPP3 – It was observed that the handle for this panel is broken.

Bus plug for panel PM – This bus plug is in room AU305 in the tower building. It was advised that the equipment which was fed from this bus plug has been removed, and the conduit dead ends in room BU301. It is recommended that this bus plug be taken out of service, and clearly marked that the equipment has been removed.

Bus plug for panel EPPGTC – It was observed that there are clearance issues for this bus plug.

Bus plug for CATH LAB #1 – It was observed that there are clearance issues for this bus plug.

Panel CPE – It was observed that the latch for this panel is broken.

Bus plug for panel CLE – It was observed that the latch on this bus plug is damaged.

Bus plug for CT SCAN (room AU104) – It was observed that the door for this bus plug is broken.

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 was made utilizing SKM Power Tools software. The software was programmed to calculate the 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 standards C37.13, C37.010, and C37.5.

The AFAULT module of the Power*Tools 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 SKM 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.

The included one-line diagram is a simplified version of the system drawings, showing only those parts of the electrical system under consideration. The various circuit locations on the diagram 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

There are two (2) separate utility feeds which provide power to the Lexington VAMC.

One utility feed is denoted “CIRCUIT 119 (P)”, and provides power to the MV gear in the Main Building through breaker 52-7. Kentucky Utilities has advised that their system is capable of delivering a maximum available three-phase short-circuit current of 10,091 Amps at 12,470V with an X/R ratio of 23.67 for this feed. Overcurrent protection for this feed is provided by CO-11 relays for both phase and ground protection.

The other utility feed is denoted “CIRCUIT 136 (Q)”, and provides power to the MV gear in the Main Building through breaker 52-1. Kentucky Utilities has advised that their system is capable of delivering a maximum available three-phase short-circuit current of 11,311 Amps at 12,470V with an X/R ratio of 21.33 for this feed. Overcurrent protection for this feed is provided by CO-11 relays for both phase and ground protection.

Refer to the one line diagram in Appendix E for more information on how the utility is connected to the system. These values determined the starting point for the analysis. No minimum or alternate switching levels were given.

4.2.2 Generator Data

There are two (2) separate generator systems present in this facility. There is one system in the main building (Drawing 1 of 10), and there is another system in the tower building (Drawing 10 of 10). The backup generation systems for each building are completely independent.

Generator data was obtained though field verification of nameplate values. Where information could not be obtained from the generator nameplates, typical values were assumed which yield conservative results.

MAIN BUILDING

There is one (1) generator in the Main Building which provides power to the emergency system.

It has been determined from the nameplate that the generator is a 660kW/825kVA generator. A subtransient reactance of 10% with and an estimated X/R ratio of 20 at 480V were assumed for this generator. 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.

TOWER BUILDING

There are two (2) generators in the Tower Building which provide power to the emergency system. These generators are connected to the system through paralleling switchgear ESB (032), and it is assumed that both generators are capable of operating simultaneously and in parallel. It has been determined from the nameplates that both generators are 1000kW/1250kVA generators.

A subtransient reactance of 10% with and an estimated X/R ratio of 23.4 at 480V were assumed for both of these generators. 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 "FEEDER INPUT DATA" computer printouts list the conductor (cable and/or busway) data used for each circuit segment. 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 diagram.

Resistance values are based on 25 degrees Celsius (room temperature) rather than the full load temperature usually shown in descriptive literature since short-circuits can occur when the circuit is initially energized or lightly loaded as well as when fully loaded. The resistance and reactance values are typical values obtained from a study of data from various conductor manufacturers.

Values are tabulated according to whether several single conductors or one multiple conductor is used and whether the conduit is steel, aluminum or plastic.

4.2.4 Transformer Data

Every effort was made to obtain accurate transformer impedance information in the field.

However, in some cases the transformer %Z value was not on the physical nameplate. In this case, a percent impedance value of 2.5% was assumed in order to facilitate a conservative analysis. The exact R and X component values used are shown on the "TRANSFORMER INPUT DATA" printouts.

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 reactances and branch-circuit conductor lengths is often difficult to obtain, assumptions regarding the motors’ subtransient reactances 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, an equivalent subtransient reactance of 0.25 pu, resulting in a fault contribution of 4 times rated current, is assumed. Larger motors (50 hp and above) have an assumed subtransient reactance of 0.2 pu, resulting in a fault contribution of 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 "CONTRIBUTION DATA" computer printouts, 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 on the "CONTRIBUTION DATA" and the "FAULT REPORT" computer printouts.

4.2.6 Assumptions and Estimates

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. Where motor sizes were not available, or motors were sized less than 50hp, motor loads were estimated based on the size of the cable and breaker feeding for the motor. These estimates are noted on the one line diagram in Appendix E.

2. For motor control centers (MCCs), motor load at each MCC was modeled as a lumped motor load of motors sized less than 50hp. The size of this lumped load was assumed based on the ampacity of the cable feeding the MCC.

3. No additional assumed motor load was modeled for this analysis. The only motor loads considered were lumped motor loads at each MCC and motors specifically called out on the one line diagrams.

4. Every effort was made to obtain correct cable data in the field. However, in some cases it was not possible to obtain cable sizes due to positioning of the cables, inability to read the size of the cables, safety concerns, etc. In these cases, the size of the cable was assumed based on the old one line diagrams and estimated size of the conductor. Cable sizes were also assumed per NEC 2011 Edition table 310.15(B)(16). These estimates are noted on the one-line diagram.

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

6. A distance of 20’ was assumed between building floors for vertical busway risers.

7. It was assumed that there is no point in the system (other that the Tower Building paralleling gear) where the two utility sources can be paralleled. Equivalently, it is assumed that for all switchgear with a tie breaker, the switchgear is never intended to operate with the tie AND both mains closed.

8. The vacuum switch at the exterior of the tower building (Drawing 5 of 10) is understood to have two utility feeds, and a single “tie” switch. Figure 4.1 shows the vacuum switch based on a received one line from the VA hospital. As shown by this drawing, the “tie” for the vacuum switch is normally open. No short circuit or arc flash case was considered with this “tie” closed, as it is assumed that this circuit configuration is not likely to occur in practice for an extended duration of time. If this configuration is expected to occur, then the analysis can be re-evaluated to include this case.

Figure 4.1 – Tower Building Vacuum Switch

4.3 Short-Circuit Analysis Results and Recommendations

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. The power systems engineer performing the study considered applicable buses and has reported bolted line-to-ground fault current when required. The results are listed in the "SHORT-CIRCUIT EVALUATION

TABLE".

Short-circuit case description: In order to estimate the short circuit current available at each point in the system, the following system configuration is considered:

All tie breakers are considered to be open, and all main breakers are considered to be closed. Fault current to the system is provided by both utility feeds. This configuration is assumed to represent the normal operating conditions for the facility.

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 following:

Motor Control Center MCC4N (Drawing 3 of 10) MCC4N (045) is inadequate with an 18kA interrupting rating for the buckets. This rating was obtained from field markings on the motor control center. It is recommended that the equipment ratings in the motor control center be verified to see if the actual motor control center rating is higher for the specific equipment in the field. Bus number 047 XFMR PP-4N PRI CB represents a breaker inside MCC4N, and is also inadequate with a rating of 18kA. This equipment is also shown in line 047 of the short circuit evaluation table.

Motor Control Center MCC3N (Drawing 3 of 10) The E4A circuit breaker in MCC3N (046) is inadequate with a rating of 18kA for available fault current of 23.066kA. The equipment ratings can be increased by replacing the breakers with ones of greater interrupting capacity provided the busing is adequate.

Panel ELPGA (Drawing 1 of 10) The E4A circuit breakers in panel ELPGA (075) are inadequate with ratings of 18kA for available fault current of 19.564kA. The equipment ratings can be increased by replacing the breakers with ones of greater interrupting capacity provided the busing is adequate.

Panel LP1C (Drawing 2 of 10) The E4A circuit breakers in panel LP1C (117) are inadequate with ratings of 18kA for available fault current of 20.379kA. Similarly, the ED4 breakers in LP1C are under rated at 18kA for available fault of 20.379kA. The equipment ratings can be increased by replacing the breakers with ones of greater interrupting capacity provided the busing is adequate.

Panel LP2C (Drawing 2 of 10) The E4A circuit breakers in panel LP2C (120) are inadequate with ratings of 18kA for available fault current of 18.691kA. The equipment ratings can be increased by replacing the breakers with ones of greater interrupting capacity provided the busing is adequate.

Panel LP4C (Drawing 3 of 10) The E4A circuit breakers in panel LP4C (127) are inadequate with ratings of 18kA for available fault current of 18.991kA. The equipment ratings can be increased by replacing the breakers with ones of greater interrupting capacity provided the busing is adequate.

Panel LPGA (Drawing 3 of 10) The E4A circuit breakers in panel LPGA (144) are inadequate with ratings of 18kA for available fault current of 26.220kA. Similarly, the E4 breakers in panel LPGA are under rated at 22kA for available fault of 26.220kA. The ED4 breakers in panel LPGA are also under rated at 18kA for available fault of 26.220kA. The equipment ratings can be increased by replacing the breakers with ones of greater interrupting capacity provided the busing is adequate.

Panel LPUH (Drawing 3 of 10) The E4A circuit breakers in panel LPUH (147) are inadequate with ratings of 18kA for available fault current of 18.855kA. Similarly, the ED4 breakers in panel LPUH are under rated at 18kA for available fault of 18.855kA. The equipment ratings can be increased by replacing the breakers with ones of greater interrupting capacity provided the busing is adequate.

Panel LP1A (Drawing 3 of 10) The E4A circuit breakers in panel LP1A (148) are inadequate with ratings of 18kA for an adjusted available fault current of 27.120kA. Similarly, the E4 breakers in panel LP1A are under rated at 22kA for an adjusted available fault of 26.821kA. The equipment ratings can be increased by replacing the breakers with ones of greater interrupting capacity provided the busing is adequate.

Panel LP2A (Drawing 3 of 10) The E4A circuit breakers in panel LP2A (151) are inadequate with ratings of 18kA for available fault current of 25.419kA. Similarly, the E4 breakers in panel LP2A are under rated at 22kA for available fault of 25.419kA. The equipment ratings can be increased by replacing the breakers with ones of greater interrupting capacity provided the busing is adequate.

Panel LP3A (Drawing 3 of 10) The E4 circuit breakers in panel LP3A (154) are inadequate with ratings of 22kA for available fault current of 25.993kA. The equipment ratings can be increased by replacing the breakers with ones of greater interrupting capacity provided the busing is adequate.

Panel LP4A (Drawing 3 of 10) The E4A circuit breakers in panel LP4A (157) are inadequate with ratings of 18kA for available fault current of 24.060kA. Similarly, the E4 breakers in panel LP4A are under rated at 22kA for available fault of 24.060kA. The equipment ratings can be increased by replacing the breakers with ones of greater interrupting capacity provided the busing is adequate.

Motor Control Center MCC#1 (Drawing 4 of 10) MCC#1 is inadequate with an 18kA interrupting rating for the buckets. This rating was obtained from field markings on the motor control center. Also, review the comments for T-PP PRI CB and Panel LP, which are located inside this motor control center. It is recommended that the equipment ratings in the motor control center be verified to see if the actual motor control center rating is higher for the specific equipment in the field.

T-PP PRI CB (Drawing 4 of 10) The primary circuit breaker for transformer T-PP in the motor control center MCC #1

(182) is inadequate with a rating of 18kA for available fault current of 32.457kA. The equipment ratings can be increased by replacing the breaker with one of greater interrupting capacity provided the busing is adequate.

Panel LP (Drawing 4 of 10) The ED4 circuit breakers in panel LP (181) are inadequate with ratings of 18kA for available fault current of 43.361kA. Similarly, the HE4A breakers in panel LP are under rated at 25kA for available fault current of 43.361kA. The equipment ratings can be increased by replacing the breakers with ones of greater interrupting capacity provided the busing is adequate.

Network Protectors T1 and T4 (Drawing 5 of 10) The network protectors T1 and T4 (200 and 203) are inadequate with a 30kA interrupting rating.

These network protectors are at the secondary of transformers T1 and T4.

SBD, SBE, SBC, SBH, SBA, SBB (Drawings 5, 6, 7, and 8) Based on obtained data, some breakers in the following switchgear may be inadequate.

SBD (208)

SBE (209)

SBC (210)

SBH (211)

SBA (212)

SBB (213)

The ratings shown in the Short Circuit Evaluation table for this equipment represent the lowest rated breaker in the switchgear. This equipment could not be accessed in the field, and as such the ratings for the breakers are based on test reports which had been obtained prior to data collection.

As these ratings could not be verified in the field, it is recommended that the equipment ratings for this equipment (switchgear bus bracing and breaker AIC rating) be verified.

Motor Control Center MCB (Drawing 5 of 10) The TED circuit breaker in motor control center MCB (223) is inadequate with a rating of 14kA for available fault current of 34.841kA. The equipment ratings can be increased by replacing the breakers with ones of greater interrupting capacity provided the busing is adequate.

Panel CLC (Drawing 5 of 10) The TED circuit breakers in CLC (250) are inadequate with ratings of 14kA for available fault current of 24.084kA. The equipment ratings can be increased by replacing the breakers with ones of greater interrupting capacity provided the busing is adequate.

Manual Transfer Switch for Panel CCU (Drawing 6 of 10) The manual transfer switch for panel CCU (260) is inadequate with a 10kA interrupting rating for an available fault current of 21.033kA. This rating was obtained from field markings on the transfer switch. There is a potential series rating that may exist if this switch is protected by Class J fuses. It is recommended that this series rating be verified and if possible appropriate overcurrent protection installed to allow for the use of a series rating.

Panel CLA (Drawing 6 of 10) The BQD circuit breakers in CLA (271) are inadequate with ratings of 14kA for available fault current of 19.432kA. The equipment ratings can be increased by replacing the breakers with ones of greater interrupting capacity provided the busing is adequate.

Panel CLG (Drawing 6 of 10) The TED circuit…