Section A 2204 Draft.pdf

HZA Engineering, LLC Mechanical & Electrical Consulting Engineers

113 W. Northern Lights Blvd, Suite 240 • Anchorage, Alaska 99503 Tel 907 562 1012 • Fax 907 562 1013 • www.hza-eng.com

Arc-Flash Hazard Analysis and Electrical Survey

Buildings 2204, 2212, & 2218

JBER, Alaska

Section A – Building 2204

AFHA and Electrical Survey

U.S. Army Engineer District, AK

Contract No. W911KB-17-D-0013

Delivery Order No. W911KB18F0090

Task Order (TO) No. 0001

Task 1

Arc-Flash Hazard Analysis and Electrical Survey Contract # W911KB-17-D-0013

Buildings 2204, 2212, & 2218 Delivery Order # W911KB18F0090

JBER, Alaska Task Order # 0001

DRAFT – October 8, 2018

Arc-Flash Hazard Analysis and Electrical Survey Section A - Building 2204

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TABLE OF CONTENTS

1. Executive Summary 3

1.1 Overview 3

1.2 Short-Circuit 3

1.3 Coordination 4

1.4 Arc-Flash 4

1.5 System Observations 5

2 Introduction 6

3 Electrical Systems Description 7

4 Short-Circuit Analysis 8

4.1 General Procedures 8

4.2 Utility Transformer Data 9

4.3 Cable Data 9

4.4 Assumptions and Estimates 9

4.5 Short-Circuit Analysis – Results and Recommendations 10

5 Overcurrent Device Coordination Study 12

5.1 General Procedures 12

5.2 Molded Case Circuit Breakers 13

5.3 Selective Coordination Considerations 14

5.4 Selective Coordination Analysis – Results and Recommendations 15

6 Arc-Flash Hazard Analysis 20

6.1 General Procedures 20

6.2 Risk Assessment and Control 21

6.3 Hazard Categories 21

6.4 Labels 23

6.5 Arc-Flash Hazard Analysis – Results and Recommendations 24

7 System Considerations 30

7.1 Cable Protection 30

7.2 System Deficiencies 30

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Appendix A: Electrical Distribution System Riser Diagram – Existing Configuration

Appendix B: Short Circuit Input Data

Appendix C: Short Circuit Analysis – Riser Diagram

Appendix D: Overcurrent Device Coordination Analysis – Existing Settings

Appendix E: Overcurrent Device Coordination Analysis – Recommended Settings

Appendix F: Overcurrent Protection Device – Existing Settings

Appendix G: Overcurrent Protection Device – Recommended Settings

Appendix H: Arc-Flash Results – Existing Settings – Normal Power

Appendix I: Arc-Flash Results – Existing Settings – Generator Power

Appendix J: Arc-Flash Results – Recommended Settings – Normal Power

Appendix K: Arc-Flash Results – Recommended Settings – Generator Power

Appendix L: Photolog/Arc-Flash Labels

Appendix M: Cost Estimate

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1. Executive Summary

1.1 Overview

This report documents the results of an Arc-Flash Hazard Analysis and Electrical Survey for

Building 2204 of the USACE district headquarter facilities at JBER, Alaska. The objective of this section is to briefly outline the results of the analysis and highlight issues and findings discovered while analyzing the building’s electrical distribution system. The full analysis is found in the main body of the report.

1.2 Short-Circuit

The maximum available fault current is the short-circuit current that occurs when all three phase conductors are shorted together and reflects the worst-case short-circuit scenario. Overcurrent protective devices are intended to interrupt fault currents and are to have interrupting ratings not less than the maximum available fault current calculated at that location. Likewise, switchboards, panelboards, and electrical equipment are intended to be rated to withstand the maximum available fault current at their terminals or bus bars to minimize damage or danger to personnel until the circuit breakers trip and clear the fault.

Of the electrical devices evaluated for Building 2204, 3 device locations were identified that are not adequately rated to interrupt or withstand the maximum available fault current that was calculated.

The following devices were noted as having more fault current than their interrupt ratings:

1. Two Glycol Pump Motor Starters (Section 1) are each rated for a maximum of 5kA.

However, the calculated fault current at each starter is 8,849A.

2. Panel M (Section 2) with breakers rated for a maximum AIR of 10kA. However, the calculated fault current is 16,023A.

3. Panel EM (Section 2) with breakers rated for a maximum AIR of 10kA. However, the calculated fault current is 10,068A.

We recommend the existing circuit breakers in these panels be replaced with new circuit breakers with higher ampere interrupting ratings (AIR) to exceed the calculated available fault current at each location. Additionally, the motor starters should either be replaced with ones with a higher short-circuit rating or current limiting breakers or fuses should be added on the line side of the motor starters to limit the available fault current to levels appropriate for existing calculated fault currents.

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1.3 Coordination

Selective coordination is meant to isolate a fault to the circuit breaker or fuse closest to the fault.

Selective coordination requires that upstream circuit breakers hold until the downstream circuit breaker trips and clears the fault.

While selective coordination is not required by the National Electrical Code (NEC) for the electrical overcurrent protective devices in Building 2204, it was discovered with this analysis that the time-current characteristic curves for a number of the circuit breakers feeding the panelboards overlap.

As a result, a fault could potentially trip not only the nearest upstream circuit breaker, but also the main circuit breaker in the MDP, transfer switch, or generator distribution panel which could deenergize most or all of the building.

Many of the existing circuit breakers have fixed settings and therefore the trip characteristics cannot be adjusted and complete selective coordination cannot be easily achieved without replacing lots of equipment. For better coordination, we recommend adjusting the settings of the existing breakers that can be adjusted to the settings as indicated in Appendix G. In conjunction with the arc-flash recommendations in Section 6.5, we also recommend replacing and adjusting the settings for new breakers and/or trip units for optimum coordination.

1.4 Arc-Flash

An arc-flash is the result of a rapid release of energy due to an arcing fault between a phase bus bar and another phase bus bar, neutral or a ground. Arc-flashes at higher available fault currents can produce enough energy to vaporize metal and cause severe burns with sufficient blast pressure to break bones or worse. The magnitude of the available arcing fault current and the length of time the fault current is available before the overcurrent protective device operates are two components that affect arc-flash energy levels.

An incident energy value of 1.2 cal/cm2 is considered the threshold of second-degree burns, while incident energy values of approximately 8-12 cal/cm2 are considered the boundary line between

“low” and “high” PPE levels, and incident energy levels of 40 cal/cm2 are considered as “maximum allowable”. Many employers have used this level of 40 cal/cm2 as a threshold above which no energized work is to be performed under any conditions due to the increased risk of non-burn injuries (hearing damage, etc.).

We analyzed the system under existing conditions and found that most of the electrical devices’ incident energy levels were under the second-degree burn threshold (1.2 cal/cm2). Thus, requiring the lowest level of PPE if worked on while energized. There were a few electrical busses that had low and mid-level incident energies and 1 location was identified that had a high energy level over

40 cal/cm2; which is not safe to work on while energized.

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Reanalyzing the system with replacement breakers and/or adjusted circuit breaker setting recommendations provided in Sections 5.4 and 7.2 of this report, we found that the incident energy levels at the branch buses changed. Some incident energy levels decreased while others increased.

The increases can be attributed to an increased time-delay between circuit breaker trip currents for better selective coordination.

We recommend replacing the circuit breakers in each of the 2 outdoor transfer switches (ATS Old -

1200 amp and ATS Annex - 800 amp) as well as the two 1200 amp circuit breakers in the outdoor generator switchboard with breakers of the same rating but with arc-energy reduction capabilities

(ERMS/RELT). Arc-energy reduction breakers can be set to trip quickly when workers are performing maintenance on the electrical system. When set to maintenance mode, the arc-flash incident energy levels will be reduced throughout the electrical system. In most cases the arc-incident levels will be less than 1.2 cal/cm2. A few panels will still have mid-level energy levels;

however, all will be under the 40 cal/cm2 threshold.

Electrical work must only be accomplished by qualified electrical workers. Protection from arc-flash hazards can best be provided by working only on circuits or equipment that have been placed in an electrically safe work condition. This could mean eliminating the potential electrical hazard completely by deenergizing the entire system. Activation of the arc-energy reduction switches

(RELT/ERMS) should occur prior to work on the electrical systems. Qualified electrical workers will need to select appropriate PPE when working on this equipment.

1.5 System Observations

Additionally, code and safety issues were noted during the site investigation and analysis of

Building 2204. A circuit breaker was not properly protecting the conductors, overload heaters were installed improperly, and neutral conductors are not isolated from the ground bar.

We recommend up sizing the conductors or reducing the circuit breaker protection rating, deenergizing the overload heater to re-install properly, and installing adequate insulators to isolate the neutral conductors from the ground conductor to improve the safety of the electrical system.

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2. Introduction

HZA Engineering performed an arc-flash hazard analysis and electrical survey of the existing electrical distribution systems at the USACE Headquarter facilities, Buildings 2204, 2212, and 2218 at JBER, Alaska. Data acquired for the analysis was obtained by NPC Energy Services during the week of August 6-10, 2018. This particular section specifically details the findings and recommendations for Building 2204. Buildings 2212 and 2218 will be addressed in separate sections. The latest version of SKM Power Tools software was used to perform the study.

The study includes a short-circuit analysis, overcurrent device time-current coordination analysis, and arc-flash hazard analysis of the building’s existing electrical systems. Additionally, arc-flash labels with equipment specific safety information will be provided and installed at the existing electrical equipment for qualified personnel to determine safe working requirements prior to working on the electrical equipment.

Arc-flash labels will be based on existing conditions and settings, as it is recognized that recommendations in this report may not be implemented immediately in full. It should be noted that modification of equipment, changes to the system configuration, adjustment of protective device settings, or failure to properly maintain equipment may invalidate these results and labels will need to be updated.

The following report outlines the findings, study results, and recommendations for better overcurrent protective device coordination and arc-flash hazard mitigation solutions in more detail as well as cost estimates to implement the recommendations.

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3. Electrical System Description

Building 2204 is comprised of two halves; one half is the original building (also referred to as Old

Building) and the other half is an addition (also referred to as New or Annex) that was constructed a number of years after the original building. Each one has its own electrical service and transfer switch, but is connected to a common back-up generator.

The back-up generator is located outdoors and is considered an optional standby system and powers the entire building when a power outage occurs. The generator is manufactured by Caterpillar and rated for 400kW, 120/208 volts 3 phase and supplies power to an outdoor freestanding generator distribution switchboard with a single main breaker and distribution breakers for feeders to two outdoor freestanding automatic transfer switches, one serving the original building, while the other serves the Annex.

The original building is fed from a 500 kVA pad mounted transformer, with a secondary voltage of

120/208 volts. The transformer is located adjacent to the building and the secondary conductors are installed underground to an outdoor free-standing automatic transfer switch where the conductors are terminated at a 1200 amp main breaker on the utility input side of the switch. This breaker is considered one of the 2 main disconnects for the entire building. Two separate feeders are tapped from the load side of the transfer switch and supply power to two different sections of the MDP

(referred to MDP Section 1 and MDP Section 2) located in a first floor electrical/mechanical room.

Each section of the MDP is rated for 800 amp 120/208 volt 3 phase and has an 800 amp rated main breaker. Feeder breakers in both sections of the MDP supply power to branch panelboards located throughout the original building. Large mechanical equipment in the original building is also supplied from this MDP.

The Annex is fed from a 150 kVA pad mounted transformer, with a secondary voltage of 120/208 volts. The transformer is located adjacent to the building and the secondary conductors are installed underground to a CT Enclosure and then to an outdoor free-standing automatic transfer switch where the conductors are terminated at an 800 amp main breaker on the utility input side of the switch. This breaker is considered one of the 2 main disconnects for the entire building. After passing through the transfer switch the conductors terminate at an 800 amp rated main circuit breaker distribution panel (referred to as MDP Annex or MDP New) located in the first floor electrical room. MDP Annex is rated for 800 amp 120/208 volt 3 phase. Feeder breakers in the

MDP Annex supply power to branch panelboards located in the first floor mechanical and electrical rooms as well as the second-floor electrical room. Large mechanical equipment in the Annex is also supplied from this MDP.

See also Appendix A: Electrical Distribution System Riser Diagram – Existing Configuration.

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4. Short-Circuit Analysis

4.1 General Procedure

The maximum available fault current is the short-circuit current that occurs when all three phase conductors are shorted together and reflects the worst-case short-circuit scenario. Overcurrent protective devices are intended to interrupt fault currents and are to have interrupting ratings not less than the maximum available fault current at that location. Likewise, switchboards, panelboards and electrical equipment are intended to be rated to withstand the maximum available fault current at their terminals or bus bars to minimize damage or danger to personnel until the circuit breakers trip and clear the fault.

This electrical system short-circuit analysis is used to compare the calculated maximum fault current with the interrupting ratings of overcurrent protective devices such as fuses and circuit breakers; to verify the adequacy of other equipment, such as switches and equipment bussing, to withstand the effects of the calculated maximum fault current levels; to assist in the selection and/or determination of settings for relays, fuses, and circuit breakers; and to provide input for the arc-flash hazard analysis.

As part of this analysis, the maximum available three-phase, RMS symmetrical, short-circuit amperes at each piece of electrical equipment in the system is calculated. The calculation procedures are based on recommendations included in applicable ANSI/IEEE standards. The SKM

Power Tools software simulates a bolted three-phase fault at the electrical equipment (switchboards, panelboards, transfer switches, etc.) and calculates the maximum available short-circuit or fault current at that point without any reduction due to current-limiting overcurrent devices which may be present. The calculated available fault current 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. 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

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X/R ratio, the more asymmetrical the fault current can be. If the calculated X/R ratio exceeds a certain level, then the increased asymmetrical duty must be considered when breaker ratings are assessed.

4.2 Utility Transformer Data

The utility company provided us with transformer and secondary conductor information for each service to the building as follows:

Original Building: The available fault current (5023.4A 3 phase, 4526.4A line to ground) at the line side of the transformer, transformer rating (500kVA), impedance (5.12%Z), secondary voltage

120/208V, secondary conductor quantity, size, and material type (3 runs of #600 awg copper), and approximate length (40 feet).

Annex: The available fault current (5049.9A 3 phase, 4554.8A line to ground) at the line side of the transformer, transformer rating (150kVA), impedance (4.6%Z), secondary voltage 120/208V, secondary conductor quantity, size, and material type (3 runs of #250 awg copper), and approximate length (20 feet to CT Enclosure).

This information, along with the building cable data mentioned below was the basis used for determining the available fault current throughout the building’s electrical system.

4.3 Cable Data

Conductor and raceway information for each feeder segment including quantity per phase, size, conductor material, insulation type, conduit type, and length were entered into the calculation model and can be referenced in the riser diagram, see Appendix B: Short Circuit Input Data.

4.4 Assumptions and Estimates

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

Assumptions or estimates are needed because of limited access, safety concerns in obtaining equipment nameplate data, or lack of documentation. The following assumptions, or estimates, were made for the reasons given above:

1. Motor loads less than 50hp were not included, since these smaller motor loads contribute an insignificant increase in short-circuit current and can be neglected according to IEEE 141-

“Recommended Practice for Electric Power Distribution and Coordination of Industrial and

Commercial Power Systems”, (Red Book).

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2. Conductor lengths were determined from the as-built plans provided, approximating the length between electrical components (feeder panel to downstream panel).

3. Conductor sizes were determined from visual inspection.

4. Unless otherwise visible, the conductors were assumed to be installed in metallic conduit.

4.5 Short-Circuit Analysis – Results and Recommendations

After performing the short-circuit calculations, the existing electrical equipment was analyzed to determine its adequacy to interrupt or withstand the effects of the calculated maximum short-circuit current at the installed locations. For some solidly grounded systems, there is a potential that the bolted three-phase fault current may not result in the maximum fault current. For this reason, the larger of the calculated bolted three phase fault current was compared with the calculated bolted line-to-ground fault current at each electrical component and the larger of the two was used for evaluating that panel’s adequacy. Calculated maximum fault currents can be seen in Appendix C:

Short Circuit Analysis – Riser Diagram.

Comparing the calculated fault currents to the Ampere Interrupt Ratings (AIR) of the circuit breakers at Building 2204 shows that most of the equipment examined was identified as adequate to interrupt or withstand the maximum short-circuit current to which they could be subjected. Of the electrical devices evaluated for Building 2204, 3 device locations were identified that are not adequately rated to interrupt or withstand the maximum available fault current that was calculated.

The following devices were noted as having more fault current than their interrupt ratings:

1. Two Glycol Pump Motor Starters (Section 1) are each rated for a maximum of 5kA.

However, the calculated fault current at each starter is 8,849A.

2. Panel M (Section 2) with breakers rated for a maximum AIR of 10kA. However, the calculated fault current is 16,023A.

3. Panel EM (Section 2) with breakers rated for a maximum AIR of 10kA. However, the calculated fault current is 10,068A.

We recommend the existing circuit breakers in these panels be replaced with new circuit breakers with higher ampere interrupting ratings (AIR) to exceed the calculated available fault current at each location. Additionally, the motor starters should either be replaced with ones with a higher short-circuit rating or current limiting breakers or fuses should be added on the line side of the motor starters to limit the available fault current to levels appropriate for existing calculated fault currents.

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For a cost estimate of these recommendations, see Appendix M: Cost Estimate.

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5. Overcurrent Device Coordination Study

5.1 General Procedure

Selective coordination is meant to isolate a fault to the circuit breaker or fuse closest to the fault.

Selective coordination requires that the upstream circuit breakers hold until the downstream circuit breaker trips and clears the fault.

A coordination study is a procedure to examine an electrical system, specifically the overcurrent protective devices, with the goal of ensuring that they are properly rated and adjusted to provide protection and maximum service continuity.

System coordination requires that the overcurrent protection devices be rated, selected, and adjusted to allow the normal load currents to flow while quickly opening the circuit when a short-circuit, overload or fault occurs. System coordination is optimized when the overcurrent protective device nearest the fault opens and isolates the faulted circuit from the electrical distribution system while keeping the remaining system in operation. When a system is selectively coordinated the overcurrent protection device must isolate the fault for the full range of available overcurrents, from overload to the maximum available fault current and for the full range of overcurrent protective device opening times associated with those currents. Selective coordination is practically impossible to achieve with standard molded case circuit breakers with “fixed” trip settings. Selective coordination typically requires the use of circuit breakers with adjustable long- & short-time delay settings and larger frame sizes to be used farther from the load or fuses to be used nearer the load.

Selectively coordinated protective devices farther from the load typically perform as a backup protection for the devices nearer to the fault and consequently must be able to hold the fault current for the time period the over current device nearest the fault takes to open. This may allow longer duration faults when the point is nearer to the service entrance equipment.

Selection and setting of the overcurrent devices are determined from comparing the time-current characteristic curves of the various devices in series on a log-log graph. This procedure considers boundaries defined by load current, short-circuit currents, and ANSI and NEC requirements.

Coordination is obtained when each device’s time-current curve shows sufficient clear space or no overlap between the curves for the protective devices operating in series. The time-current characteristic curves are plotted along the fault current axis until the maximum available fault current is achieved for the device. Selective coordination is achieved when the curves do not overlap up to the level of the maximum available fault current indicated where the time-current characteristic curve for each device ends on the short-circuit current axis.

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5.2 Molded Case Circuit Breakers

Molded case circuit breakers typically will not fully coordinate into the instantaneous region

(approximately half cycle) unless time delays are provided in the circuit breakers further from the load. This condition is indicated in Figure 1 where circuit breaker B overlaps with circuit breaker

A in the instantaneous region. Circuit breaker C is fully coordinated with circuit breakers A & B since the time-current characteristic curve for circuit breaker C does not overlap for the full range of fault currents from the instantaneous fault region (initial period from 0 to a few milli-seconds), through the short-time region (middle region from a fraction of a second to a few seconds), to the long-time fault region (usually ranging from many seconds to multiple minutes).

Figure 1 – Example Molded Case Circuit Breaker Coordination

Greater separation between the instantaneous settings may increase the likelihood that the two devices will operate selectively. The potential lack of selective coordination is generally not considered critical, and can be avoided by adopting a different and, in general, less economical design, especially when the following are considered:

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1. Most faults occur in equipment such as motors, lighting panels, and process control panels which typically are located at the end of branch circuits, significantly reducing fault level and thereby reducing or eliminating the possibility of non-selective operation.

2. Lower magnitude arcing faults in rotating machinery and lighting panels are statistically more common than bolted three-phase faults.

3. Ground faults are more common than three-phase faults.

4. Maximum fault current is a random event depending on point-on-wave the fault occurs.

Other factors include X/R ratio, power factor, frequency, phase angle, and magnitude of the symmetrical fault current.

5. The device cutoff points on time-current coordination graphs are based on bolted fault current levels which correspond to zero impedance. Typical fault current impedance is usually greater than zero so the actual fault current seen by overcurrent devices can be less than what is shown on the time-current coordination graphs.

5.3 Selective Coordination Considerations

The objective is to determine the best coordination for the entire system, however, selective coordination is not always considered essential or economically viable unless required for the continuation of the electrical service for safety considerations.

Selective coordination is often difficult to achieve when overcurrent devices with fixed settings are used. Selective coordination typically requires upstream panels to have larger bussing and circuit breaker frame sizes with adjustable circuit breaker settings. Greater selectivity generally requires longer holding times which can adversely affect arc-flash.

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. This approach necessitates tradeoffs in selectivity for some parts of the system to achieve maximum coordination in more critical areas.

The NEC does not require all electrical systems to be selectively coordinated in all facilities.

Instead, the NEC requires selective coordination for only a few electrical systems, such as: certain health care facilities, emergency power systems, legally required standby systems, critical operations power or data systems, and where multiple elevators are fed from a single feeder.

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5.4 Selective Coordination Analysis – Results and Recommendations

The results of the coordination study are the time-current characteristic graphs; which show the degree of coordination between each of the overcurrent protective devices connected in series in this electrical system. Smaller overcurrent devices with fixed time-current characteristics are not shown on the graphs unless they directly affect the setting of an adjustable upstream device.

It is our understanding that Building 2204 does not have the functions or electrical system features that the NEC requires to be selectively coordinated. Although selective coordination is not required, we have reviewed the time-current characteristic curves and noted that some of the circuit breakers in the existing electrical distribution system overlap. As a result, a fault could potentially trip not only the nearest upstream circuit breaker but also further upstream circuit breakers; which could deenergize multiple panelboards.

Unless otherwise indicated, circuit breakers in series with each other, and no other breakers or loads, are not addressed in this report. Coordination between these breakers is not required and will not have any affect, as a fault at either bus will have the same result.

Specific devices lacking selective coordination are as follows:

1. The main disconnect (800 amp) in the ATS Annex has time-current characteristics that overlap with the main circuit breaker (800 amp) in the MDP Annex. However, these breakers are in series, with no other breakers and a fault at either bus will have the same result. Therefore, coordination between these breakers is not required and will not have any affect.

However, in conjunction with the arc-flash recommendations in Section 6.5, We recommend, replacing the existing 800 amp breaker in the ATS with one that has better time-current characteristics and adjusting the settings as indicated in Appendix G.

2. The main circuit breaker (800 amp) in the MDP Annex has time-current characteristics that overlap with the elevator feeder circuit breaker (200 amp) and the Panel M feeder circuit breaker 225 amp). As a result, a fault below either the 200 amp breaker or 225 amp breaker could potentially trip the MDP main circuit breaker (800 amp); which could deenergize the entire service to the Annex.

For better coordination, we recommend adjusting the settings of the existing 800 amp main circuit breaker as indicated in Appendix G.

3. The main disconnect (1200 amp) in ATS Old has time-current characteristics that overlap with the main circuit breakers (800 amp) in MDP Section 1 and Section 2. As a result, a fault below the 800 amp breaker could potentially trip the main disconnect (1200 amp); which could deenergize the entire service to the Old Building.

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For better coordination, we recommend adjusting the settings of the existing 800 amp main circuit breakers as indicated in Appendix G. In conjunction with the arc-flash recommendations in Section 6.5, we also recommend, replacing the existing 1200 amp breaker trip unit with one that has better time-current characteristics and adjusting the settings as indicated in Appendix G.

4. The main circuit breaker (800 amp) in MDP Section 1 has time-current characteristics that overlap with the Panel B, E, H feeder circuit breaker (300 amp). As a result, a fault below the

300 amp breaker could potentially trip the MDP Section 1 main circuit breaker (800 amp);

which could deenergize multiple panelboards.

For better coordination, we recommend adjusting the settings of the existing 300 amp feeder circuit breaker as indicated in Appendix G. This will provide better coordination with upstream circuit breakers; however, it will reduce the coordination with downstream circuit breaker Panel

H.

5. The Panel A, D, G feeder circuit breaker (300 amp) has time-current characteristics that overlap with the Panel G and GG (225 amp) main circuit breakers. As a result, a fault below the 225 amp breakers could potentially trip the Panel A, D, G feeder circuit breaker (300 amp); which could deenergize multiple panelboards.

circuit breaker as indicated in Appendix G. This will provide better coordination with downstream circuit breakers. However, complete coordination cannot be achieved through setting adjustments without causing less coordination with upstream circuit breakers.

Coordination is not required and we do not recommend any other coordination efforts as complete coordination cannot be easily achieved without replacing equipment.

6. The Panel B, E, H feeder circuit breaker (300 amp) has time-current characteristics that overlap with the Panel H (225 amp) circuit breaker. As a result, a fault below the 225 amp breaker could potentially trip the Panel B, E, H feeder circuit breaker (300 amp); which could deenergize multiple panelboards.

circuit breaker as indicated in Appendix G. This will provide better coordination with upstream circuit breakers. However, complete coordination cannot be achieved through setting adjustments without causing less coordination with downstream circuit breakers. Coordination is not required and we do not recommend any other coordination efforts as complete coordination cannot be easily achieved without replacing equipment.

7. The Panel C, F, J feeder circuit breaker (300 amp) has time-current characteristics that overlap with the Panel J and JJ (225 amp) circuit breakers. As a result, a fault below the 225 amp

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We do not recommend adjusting settings for either breaker. Adjusting settings will cause an overlap with the upstream MDP Section 1 (800 amp) circuit breaker. Coordination is not required and we do not recommend any other coordination efforts as complete coordination cannot be easily achieved without replacing equipment.

8. The Panel U feeder circuit breaker (225 amp) in the MDP Section 2 has time-current characteristics that overlap with the circuit breaker disconnect (150 amp) for Panel Server room.

As a result, a fault below the 150 amp breakers could potentially trip the Panel U feeder circuit breaker (225 amp); which could deenergize the Panel Server room and Panel U.

For better coordination, we recommend adjusting the settings of both breakers as indicated in

Appendix G. However, complete coordination cannot be achieved through setting adjustments.

9. The Panel U feeder circuit breaker (225 amp) in the MDP Section 2 has time-current characteristics that overlap with the main circuit breaker (125 amp) in Panel U. As a result, a fault below the 125 amp breakers could potentially trip the nearest upstream circuit breaker (125 amp) and the Panel U feeder circuit breaker (225 amp); which could deenergize multiple panelboards.

For better coordination, we recommend adjusting the settings of both breakers as indicated in

Appendix G. However, complete coordination cannot be achieved through setting adjustments.

10. The Panel M feeder circuit breaker (225 amp) in MDP Section 2 has time-current characteristics that overlap with the Panel MR feeder circuit breaker (60 amp) and the MCC feeder circuit breaker (50 amp) in Panel M. As a result, a fault below the 50 or 60 amp breakers could potentially trip the Panel M feeder circuit breaker (225 amp) in MDP Section 2; which could

For better coordination, we recommend adjusting the settings of the existing 225 amp feeder circuit breaker as indicated in Appendix G. However, complete coordination cannot be achieved through setting adjustments. Coordination is not required and we do not recommend any other coordination efforts as complete coordination cannot be easily achieved without replacing equipment.

11. The Panel 1 feeder circuit breaker (125 amp) in MDP Section 2, has time-current characteristics

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Page -18 that overlap with the main circuit breaker (225 amp) in Panel 1, and the Panel 3 feeder circuit breaker (125 amp). However, the 125 amp feeder breaker in MDP Section 2 and the 225 amp main circuit breaker in Panel 1 are in series with no other breakers and a fault at either bus will have the same result. Coordination between these breakers is not required.

We offer no recommendations for better coordination between the Panel 1 feeder breaker (125 amp) in MDP Section 2 and the Panel 3 feeder breaker (125 amp) in Panel 1 as the Panel 3 feeder circuit breaker has fixed settings; while the upstream 125 amp circuit breaker is already set to the highest setting. Coordination is not required and we do not recommend any other coordination efforts as complete coordination cannot be easily achieved without replacing equipment.

12. The main circuit breaker (800 amp) in MDP Section 2 has time-current characteristics that overlap with the Panel Elevator feeder circuit breaker (400 amp) in MDP Section 2. As a result, a fault below the 400 amp breaker could potentially trip the MDP Section 2 main circuit breaker

(800 amp); which could deenergize multiple panelboards.

For better coordination, we recommend adjusting the settings of the 400 amp breaker as indicated in Appendix G. However, complete coordination cannot be achieved through setting adjustments. Coordination is not required and we do not recommend any other coordination efforts as complete coordination cannot be easily achieved without replacing equipment.

13. The Panel Elevator feeder circuit breaker (400 amp) in MDP Section 2 has time-current characteristics that overlap with the Elevator feeder circuit breaker (225 amp). As a result, a fault below the 225 amp breaker could potentially trip the Panel Elevator feeder circuit breaker

(400 amp) in MDP Section 2; which could deenergize multiple panelboards.

For better coordination, we recommend adjusting the settings of the 225 amp breaker as indicated in Appendix G. However, complete coordination cannot be achieved through setting adjustments. Coordination is not required and we do not recommend any other coordination efforts as complete coordination cannot be easily achieved without replacing equipment.

14. The Panel Elevator feeder circuit breaker (400 amp) in MDP Section 2 has time-current characteristics that overlap with the Panel EM feeder circuit breaker (125 amp). As a result, a fault below the 125 amp breaker could potentially trip the Panel Elevator feeder circuit breaker

(400 amp) in MDP Section 2; which could deenergize multiple panelboards.

Complete coordination cannot be achieved through setting adjustments without causing less coordination with upstream circuit breakers. Coordination is not required and we do not recommend any other coordination efforts as complete coordination cannot be easily achieved without replacing equipment.

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15. The generator switchboard existing circuit breaker settings were not able to be determined as they are not visible unless the generator is turned on. We assumed worst-case settings. With this assumption, the main circuit breaker disconnect (1200 amp) in the generator switchboard has time-current characteristics that overlap with the generator switchboard feeder circuit breakers

(600 amp and 1200 amp) as well as all three of the main breakers in the MDPs (MDP Annex, MDP Section 1, and MDP Section 2). As a result, a fault below the main breakers in the MDPs could potentially trip the main breaker in the Generator Switchboard (1200 amp); which could deenergize the entire building.

For better coordination, and in conjunction with the arc-flash recommendations in Section 6.5, we recommend, replacing both 1200 amp breaker trip units with new trip units that have better time-current characteristics and adjusting the settings for the remaining 4 breakers as indicated in Appendix G.

See Appendix D: Overcurrent Device Coordination Analysis – Existing Settings for existing circuit breaker time-current curves and settings.

See Appendix E: Overcurrent Device Coordination Analysis – Recommended Settings for recommended circuit breaker time-current curves and settings.

See Appendix F: Overcurrent Protection Device – Existing Settings for existing circuit breaker settings.

See Appendix G: Overcurrent Protection Device – Recommended Settings for recommended circuit breaker settings.

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6. Arc-Flash Hazard Analysis

6.1 General Procedures

An arc-flash is the result of a rapid release of energy due to an arcing fault between a phase bus bar and another phase bus bar, neutral or a ground. Most faults occur during maintenance or during manual operation of the equipment, such as closing a circuit breaker under short-circuit or dropping a tool on the live bus bars, etc. The electrical arc lasts until the opening of the overcurrent protective device on the supply side of the fault. Arc-flashes at higher available fault currents can produce enough energy to vaporize metal and cause severe burns with sufficient blast pressure to break bones or worse. The magnitude of the available arcing fault current and the length of time the fault current is available before the overcurrent protective device operates are two components that affect arc-flash energy levels.

An arc-flash hazard analysis was performed for the existing electrical systems at Building 2204 to determine the arc-flash hazards that currently exist and provide recommendations to mitigate these hazards.

The arc-flash hazard analysis was calculated using SKM Power Tools with the IEEE 1584-2018 calculation method. The IEEE 1584 analysis procedure begins with a complete data collection of the existing power system. Characteristics of the power source – utility and generator – and the power system components such as: transformers, cables, and the tripping characteristics of overcurrent protective devices, are all entered into the computer program. The program first calculates the bolted 3-phase short-circuit current at each bus of concern in the system. Then the arc-fault current is calculated at each bus location. Next, under the arc-fault current condition, the clearing time of the protective device protecting the bus is determined. For fuses, the manufacturer’s total clearing time is used. For low voltage breakers, the right-hand side of the manufacturer’s time-current curve band is used. For relayed medium voltage breakers, the relay’s curve shows only the relay operating time, consequently, the particular breaker’s opening time must be added to this time. Following the clearing time determination, the working distance at each bus is selected. Next, incident energies are calculated for each bus. Incident energy is the amount of energy impressed on the face and body of the electrical worker. One of the units used to measure incident energy is calories/cm2. The flash protection boundary based on an incident energy of 1.2 calories/cm2 is calculated. This is the generally accepted energy level that causes the onset of a second-degree burn. Finally, the hazard risk category and the worker’s personal protection equipment (PPE) for each bus under consideration are determined.

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6.2 Risk Assessment and Control

NFPA 70E indicates a “hierarchy of controls” when controlling risk.

1. This hierarchy prioritizes the elimination of the hazard as the first priority. For electrical hazards, this typically means removing unnecessary equipment or eliminating the need to expose energized parts. It can also mean de-energizing equipment and creating an electrically safe condition which also eliminates electrical hazards.

2. When hazard elimination is not possible, the next priority is substitution. For example, this may mean replacing older electrical equipment with newer equipment designed to reduce risk.

3. The third risk control method in the hierarchy of controls is engineering controls. For electrical hazards, engineering controls may be the addition of cover plates, shielding to prevent exposure to energized parts, or simply changing circuit breaker trip settings.

4. The fourth risk control method in the hierarchy is awareness and administrative controls.

Examples of awareness and administrative controls may be written procedures, signage and training used to restrict access to hazard areas.

5. Finally, the least effective risk control method and the last choice in the hierarchy of controls to reduce risk is to protect the worker with personal protective equipment (PPE).

6.3 Hazard Categories

The SKM Power Tool software can calculate the arc-flash hazard for each bus, motor starter, disconnect, etc. The hazard will be referred to as incident energy. The incident energy will be calculated in calories per centimeter squared (Cal/cm2). There are also tables that show this energy in joules per centimeter squared (J/cm2). For the purposes of this report Cal/cm2 will be used as this is the standard in the NFPA 70E.

When selecting the appropriate PPE to work on equipment, 2018 NFPA 70E, 130.5(F) allows for two separate methods: The Incident Energy Analysis Method and the Arc-Flash PPE Category

Method. NFPA 70E states that “Either, but not both, methods may be used on the same piece of equipment. The results of an incident energy analysis to specify an arc-flash PPE category in Table

130.7(C)(15) shall not be permitted.” Both methods will be explained below, however this analysis calculates the incident energy and therefore the Incident Energy Analysis Method should used to select the appropriate PPE.

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With the Incident Energy Analysis Method, the incident energy at each electrical device is calculated and the appropriate PPE is selected from Table 130.5(g) of NFPA 70E (2018):

Incident energy exposures equal to 1.2 Cal/cm2 up to 12 Cal/cm2

Arc-rated clothing with an arc rating equal to or greater than the estimated incident energy

Long-sleeve shirt and pants or coverall or arc-flash suit (SR)

Arc-rated face shield and arc-rated balaclava or arc-flash suit hood (SR)

Arc-rated outerwear (e.g., jacket, parka, rainwear, hard hat liner) (AN)

Heavy-duty leather gloves, arc-rated gloves, or rubber insulating gloves with leather protectors

(SR)

Hard hat

Safety glasses or safety goggles (SR)

Hearing protection

Leather footwear

Incident energy exposures greater than 12 Cal/cm2

Arc-rated clothing with an arc rating equal to or greater than the estimated incident energy

Long-sleeve shirt and pants or coverall or arc-flash suit (SR)

Arc-rated arc-flash suit hood

Arc-rated outerwear (e.g., jacket, parka, rainwear, hard hat liner) (AN)

Arc-rated gloves or rubber insulating gloves with leather protectors (SR)

Hard hat

Safety glasses or safety goggles (SR)

Hearing protection

Leather footwear

When using this table, the minimum PPE rating must exceed the maximum incident energy calculated on the report for the specific piece of equipment to be accessed; PPE may be layered. All the PPE is required in the categories listed above.

With the Arc-Flash PPE Category Method, the estimated maximum available fault current, maximum fault clearing times, and minimum working distances for each electrical device is needed before determining the Arc-Flash PPE category from Table 130.7(C)(15)(a) of NFPA 70E (2018).

Once the Arc-Flash PPE category is determined, the appropriate PPE can be selected from Table

130.7(C)(15)(c) of NFPA 70E (2018), being mindful not to exceed the Cal/cm2 listed in each category.

Category 1 Arc-rated clothing of at least 4 Cal/cm2.

This must include arc-rated long sleeves and long pants or arc-rated coveralls. Also required is an arc-rated face shield or an arc-rated flash suit hood.

Category 2 Arc-rated clothing of at least 8 Cal/cm2.

This must include arc-rated long sleeves and long pants or arc-rated coveralls. Also required is an arc-rated face shield combined with an arc-rated balaclava or an arc-rated flash suit hood.

Category 3 Arc-rated clothing that provides a minimum of 25 Cal/cm2.

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This system of arc-rated clothing may consist of any combination of the following provided that the chosen combination has been tested and verified to provide the required level of arc-flash protection: arc-rated long sleeves, arc-rated long pants, arc-rated coveralls, arc-rated flash suit pants and arc-rated flash suit jacket. Also required is an arc-rated flash suit

Category 4 Arc-rated clothing that provides a minimum of 40 Cal/cm2.

This system of arc-rated clothing may consist of any combination of the following provided that the chosen combination has been tested and verified to provide the required level of arc-flash protection: arc-rated long sleeves, arc-rated long pants, arc-rated coveralls, arc-rated flash suit pants and arc-rated flash suit jacket.