Section B 2212 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 B – Building 2212

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 B - Building 2212

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TABLE OF CONTENTS

1. Executive Summary 3

1.1 Overview 3

1.2 Short-Circuit 3

1.3 Coordination 3

1.4 Arc-Flash 4

1.5 System Observations 4

2 Introduction 5

3 Electrical Systems Description 6

4 Short-Circuit Analysis 7

4.1 General Procedures 7

4.2 Utility Transformer Data 8

4.3 Cable Data 8

4.4 Assumptions and Estimates 8

4.5 Short-Circuit Analysis – Results and Recommendations 9

5 Overcurrent Device Coordination Study 10

5.1 General Procedures 10

5.2 Molded Case Circuit Breakers 10

5.3 Selective Coordination Considerations 12

5.4 Selective Coordination Analysis – Results and Recommendations 12

6 Arc-Flash Hazard Analysis 14

6.1 General Procedures 14

6.2 Risk Assessment and Control 15

6.3 Hazard Categories 15

6.4 Labels 17

6.5 Arc-Flash Hazard Analysis – Results and Recommendations 18

7 System Considerations 20

7.1 Cable Protection 20

7.2 System Deficiencies 20

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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

Appendix I: Arc-Flash Results – Recommended Settings

Appendix J: Photolog/Arc-Flash Labels

Appendix K: 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 2212 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 2212, all were found to be adequately rated to interrupt or withstand the maximum available fault current that was calculated.

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 2212, it was discovered with this analysis that the time-current characteristic curves for the main service disconnect, main circuit breaker in the MDP, and the Panel P feeder breaker overlap; indicating a lack of selective coordination.

Three circuit breakers (200 amp main service disconnect, 225 amp main circuit breaker in MDP, and 150 amp Panel P feeder breaker) overlap through all regions of the time-current curve plot. As a result, a fault below the 150 amp breaker could potentially trip not only the nearest upstream circuit breaker (150 amp), but also the upstream breakers (200 amp and 225 amp) which could deenergize not only Panels P and L, but also the MDP.

These circuit breakers have fixed settings and therefore the trip characteristics cannot be adjusted.

We recommend replacing the 150 amp circuit breaker with a 100 amp breaker to address a code violation indicated in Sections 1.5 and 7.2. In addition, the replacement circuit breaker will allow

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Page -4 for better selective coordination with the upstream circuit breakers by manipulating the time-delay of the Panel P feeder breaker.

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.).

After analyzing the existing system under existing conditions, we found that all of the electrical devices downstream of the main service disconnect had incident energy levels less than the second-degree burn threshold (1.2 cal/cm2). However, at the 200 amp main service disconnect, the calculated incident energy level was 15.3 cal/cm2.

Although this is much higher than at the other devices, it is still under the 40 cal/cm2 threshold. We do not offer any recommendations to lower the arc-flash incident levels. 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 2212. An equipment grounding conductor was not terminated and a feeder circuit breaker had a rating in excess of the two panelboards that it supplies power to.

Terminating the ground conductor and replacing the breaker with one that has an overcurrent protection rating that will protect the conductors will 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 2212. Buildings 2204 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 2212 is fed from (3) 50 kVA, pole mounted transformers with a secondary voltage of

120/208 volts. The feeders are installed underground to the building, before terminating at a 200 amp rated circuit breaker main service disconnect mounted on the exterior of the building. The feeder from the main service disconnect enters the building and terminates at a 225 amp rated main circuit breaker in the Main Distribution Panel (MDP). A feeder circuit breaker from the MDP supplies power to Panels P and L rated for 150 amps.

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

For Building 2212, the electrical utility company provided us with the available fault current

(5,298.9A 3 phase, 4843.2A line to ground) at the line side of the transformer, transformer rating (3 x 50kva), impedance (1.8%Z), secondary voltage 120/208V, secondary conductor quantity, size, and material type (1 run of #1/0 transitioned to 3/0 awg copper), and approximate length (248 feet).

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).

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.

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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 existing circuit breakers at Building 2212, confirms that all of the equipment examined were identified as adequate to interrupt or withstand the maximum short-circuit current to which they could be subjected.

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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.

5.2 Molded Case Circuit Breakers

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

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(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:

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.

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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.

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 2212 does not have the functions or electrical system features

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Page -13 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.

Specific devices lacking selective coordination are as follows:

1. The main disconnect circuit breaker (200 amp) and the main breaker (225 amp) in the MDP overlap in all three regions (instantaneous, short-time, and long-time) of the time-current curve plot. 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.

2. The main circuit breakers (200 amp disconnect and 225 amp MDP main) overlap with a downstream breaker (150 amp) in all three regions (instantaneous, short-time, and long-time) of the time-current curve plot. As a result, a fault below the 150 amp breaker could potentially trip not only the nearest upstream circuit breaker (150 amp), but also the upstream breakers (200 amp and 225 amp) which could deenergize not only Panels P and L, but also the MDP. These circuit breakers have fixed settings and therefore the trip characteristics cannot be adjusted.

Replacing the 150 amp breaker with a 100 amp breaker to address the code violation referenced in Section 7.2, does allow for better coordination between the Panel P feeder breaker and the upstream breakers. Additional coordination is not required and we do not recommend any other coordination efforts as complete coordination cannot be easily achieved without replacing equipment.

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.

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

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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 2212 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 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. Also required is an arc-rated flash suit

Each of the four arc-flash PPE categories (Arc-Flash PPE Category Method) also requires the following protective equipment: voltage-rated hardhat, safety glasses or safety goggles, ear canal insert-type hearing protection, leather footwear and leather gloves or voltage rated gloves with leather protectors. In addition, categories 3 and 4 requires that gloves be arc-rated.

The PPE categories have been streamlined in the 2018 NFPA 70E. Previous versions have an addi-tional category 0. Category 0 was ranged from 0-1.2 Cal/cm2. This meant that Category 1 ranged from 1.2-4 Cal/cm2. This change was made due to the understanding that any incident energy could cause injury and/or damage whether it be burn, hearing damage, blindness (temporary or perma-nent) or worse at any level. This allowed for protection at all levels of incident energy.

In all cases, the arc-flash boundary, must be adhered to. Inside this boundary the appropriate PPE must be worn only to be removed after exiting the boundary. To reduce these boundaries, it may be necessary to de-energize the gear or use an approved energy reduction management system (ERMS) or reduced energy let through system (RELT). In general, this will effectively reduce the boundary and incident energy.

6.4 Labels

Arc-Flash labels have been generated and can be found in Appendix J: Photolog/Arc-Flash Labels.

Labels will also be applied to each switchboard, panelboard, and motor control center to provide as a minimum the following information: panel designation, nominal voltage, Arc-Flash Incident

Energy, arc-flash boundary, approach boundaries, and Personal Protection Equipment (PPE) requirements. This information will be used by qualified electrical workers to assess existing conditions, establish boundaries, and determine appropriate PPE to work on the equipment

The arc-flash boundary as defined is the distance from the equipment at which someone could be exposed to heat equaling 1.2 cal/cm2, the amount required to cause second-degree burns. To cross this boundary, a person must use arc-rated protective equipment.

There are two approach boundaries for shock protection: Limited Approach Boundary and the

Restricted Approach Boundary. The Limited Approach Boundary is the shock protection boundary

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Page -18 farthest away from exposed energized electrical conductors or circuit parts and is established to keep unqualified persons a safe distance from exposed energized parts. Unqualified workers may not cross the Limited Approach Boundary unless briefed on the hazards and continuously escorted by a qualified person. The Restricted Approach Boundary is the shock protection boundary closest to the exposed energized parts and may only be crossed by qualified electrical workers following safe electrical work-practices which include wearing appropriate shock protection and using insulated tools.

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.

6.5 Arc-Flash Hazard Analysis – Results and Recommendations

The results of the arc-flash hazard analysis as presented in this report are based on the IEEE 1584 calculation procedures and assume that protective devices considered are in working order and will operate within their specified tolerances to clear faults from the system.

The full results can be found at the end of this report in Appendix H, and Appendix I, where each electrical bus (panel, switchboard, motor control center, transfer switch, etc.) is identified with corresponding voltage, working distance, fault current, incident energy, arc-flash boundary, and

PPE requirements.

The values shown in the arc-flash hazard analysis assume that the fault is cleared by the upstream protective device; even if the equipment contains a main overcurrent protective device. This assumption is intended to produce conservative results and therefore cover the case where faults originating in such equipment may propagate to the line side of the local main breaker. The calculations are cut off at a maximum arcing duration of 2.0 seconds.

A conservative fault current value may not reveal the worst-case Arc-Flash incident energy values that may be present. Lower fault currents sometimes result in higher arc-flash energies because a protective device may take longer to operate and extinguish the arc.

For reference, 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 an incident energy level of 40 cal/cm2 is considered as

“maximum allowable”.

While NFPA 70E does not explicitly prohibit work at locations with energy levels above 40 cal/cm2, research into the potential for non-burn injuries (internal injuries, hearing damage, etc.)

JBER, Alaska Task Order # 0001

Page -19 indicates that these other injuries become a significant concern at such high-energy locations. NFPA

70E does not define protective clothing classes with arc-ratings above 40 cal/cm2 and many employers have used this level as a threshold above which no energized work is allowed under any conditions due to the increased risk of non-burn injuries (hearing damage, etc.).

Achieving lower arc-flash incident energy targets, requires faster tripping of the overcurrent protective devices. This is somewhat contrary to the goal of selective coordination; where the upstream overcurrent protective devices are intentionally adjusted to hold for longer trip times to allow for the downstream devices nearest a fault to open and isolate the fault while keeping the remaining system in operation. As such, a compromise must be made between selective coordination or expensive mitigation systems.

We analyzed the system under existing conditions and found that all of the electrical device’s incident energy levels downstream of the main service disconnect were under the second-degree burn threshold (1.2 cal/cm2). Thus, requiring the lowest level of PPE if worked on while energized.

However, at the main disconnect, the calculated incident energy level was 15.3 cal/cm2. Although this is much higher than at the other devices, it is still under the 40 cal/cm2 threshold. Qualified electrical workers will need to select appropriate PPE when working on this equipment.

After reanalyzing the system with the replacement circuit breaker recommendations provided in

Sections 5.4 and 7.2 of this report, we found that the incident energy levels at the branch buses were slightly reduced. Alternatively, the energy level at the MDP increased to 9.2 cal/cm2. The higher incident energy level is in response to the increased time-delay between circuit breaker trip currents.

Although the incident energy level has increased, it is still under the 40 cal/cm2 threshold and will result in better selective coordination of the electrical system. We do not offer any other recommendations for lowering the arc-flash incident energy levels.

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.

For Arc-Flash results, corresponding to existing devices and settings connected to normal utility power, see Appendix H: Arc-Flash Results – Existing Settings.

For Arc-Flash results, corresponding to recommended devices and settings connected to normal utility power, see Appendix I: Arc-Flash Results – Recommended Settings.

JBER, Alaska Task Order # 0001

Page -20

7. System Considerations

7.1 Cable Protection

The National Electrical Code (NEC), article 240 requires that conductors be protected against overcurrent in accordance with their ampacities specified in NEC 310.15. Feeder overcurrent protective devices were reviewed to verify that the load side conductors are protected in accordance with NEC Articles 240 and 310. The analysis however, does not consider adjustment factors such as for voltage drop or conduit fill.

Conductors appeared to be adequately protected as required by the NEC, however we noted that the ampacity rating of the Panel P feeder conductors is rated less than the ampacity rating of the protecting circuit breaker. In this particular case, it would be a concern if the load exceeds the rating of the conductor but not the overcurrent protective device rating. The NEC has a provision that allows for the next higher standard overcurrent device rating (above the ampacity for the conductors being protected) where a set of conditions are met. One of the conditions is that the ampacity of the conductors does not correspond with the standard ampere rating of a fuse or circuit breaker.

7.2 System Deficiencies

As part of the site survey and analysis at Building 2212, we noticed the following additional issues and code violations:

1. An equipment grounding conductor is loose in the MDP and is not connected to the ground bar or ground lug. Since the grounding conductor is not terminated, there is no return path to ground. We recommend that a ground bar be installed and the grounding conductor be properly terminated.

2. The 150 amp feeder circuit breaker in the MDP that supplies Panels P and L is rated in excess of the Panel P and L ratings. As a result, Panels P and L are not adequately protected.

We recommend that the 150 amp circuit breaker be removed and replaced with a 100 amp circuit breaker that protects the feeder and panels.

JBER, Alaska Task Order # 0001

Appendix A

Electrical Distribution System Riser Diagram

Existing Configuration

BUILDING 2212 - ELECTRICAL DISTRIBUTION SYSTEM - RISER DIAGRAM

EXISTING CONFIGURATION - AUGUST 6, 2018

ENGINEERING SOLUTIONS

Tel. (907) 562-1012 Fax (907) 562-1013

113 W. Northern Lights Blvd., Suite 240 Anchorage, Alaska 99503

AK Corporation #: AECL881

JBER, Alaska Task Order # 0001

Appendix B

Short Circuit Input Data

Project: 2212 RECOMMENDED

Base Project

DAPPER Fault Analysis Input Report (English)

Utilities

Contribution From Name

Bus Name

In/Out Service

Nominal Voltage

-------- Contribution Data --------

Duty Units X/R

PU (100 MVA Base)

R PU

X PU

UTILITY T-PRIMARY In 12,470 3P:

SLG:

5,299 Amps 15.00

4,843 Amps 15.00

Pos: 0.058

Zero: 0.075

0.872

1.118

Cables

Cable From Bus

Name To Bus

In/Out Qty

Service /Ph Length

Feet

Size

------ Cable Description

Cond. Type

Duct Type Insul

Per Unit (100 MVA Base)

R pu jX pu

CBL- DISC TO MDP MAIN DISCONNECT

MDP

In 1 10 3/0 Copper Magnetic XLPE Pos:

Zero:

1.9323

6.0743

0.8506

2.4154

CBL-PANEL L PANEL P

PANEL L

In 1 5 1 Copper Magnetic Pos:

Zero:

1.8491

2.9401

0.6587

1.6758

CBL-PANEL P MDP

PANEL P

In 1 82 1 Copper Magnetic Pos:

Zero:

30.3254

48.2175

10.8034

27.4824

CBL-SECONDARY T SECONDARY

MAIN DISCONNECT

In 1 248 3/0 Copper - XLPE Pos:

Zero:1 47.9216

50.6435

16.8528

47.9216

2-Winding Transformers

Xformer In/Out ------------------Primary & Secondary--------------- Nominal Z PU (100 MVA Base)

Name Service Bus Conn. Volts FLA kVA R pu jX pu

Xformer In/Out ------------------Primary & Secondary--------------- Nominal Z PU (100 MVA Base)

Name Service Bus Conn. Volts FLA kVA R pu jX pu

T UTILITY #88,89,91In T-PRIMARY D 12,470 12 150.0 Pos: 2.9840 11.6233

T SECONDARY WG 208 718 Zero: 2.9840 11.6233

JBER, Alaska Task Order # 0001

Appendix C

Short Circuit Analysis

Riser Diagram

UTILITY

SP

T UTILITY #88,89,90

150 kVA Pri Delta Sec Wye-Ground Z% 1.8000 %

T-PRIMARY

Nominal 12470.0 V 3P 5298.90 A

SLG 4843.20 A

T SECONDARY

Nominal 208.0 V 3P 21583.92 A

SLG 22076.32 A

CBL-SECONDARY

Size 3/0 AWG 1 Runs/Phase Insulation XLPE Class TECK90 Raceway - Length 248.0 ft

MDP

Nominal 208.0 V 3P 5366.63 A

SLG 3433.48 A CB PANEL P

Sensor/Trip 150.0 A Plug 150.0 A

CBL-PANEL P

Size 1 AWG 1 Runs/Phase Insulation Class XHHW Raceway Magnetic Length 82.0 ft

CBL-PANEL L

Size 1 AWG 1 Runs/Phase Insulation Class XHHW Raceway Magnetic Length 5.0 ft

PANEL P

Nominal 208.0 V 3P 3539.55 A

SLG 2418.22 A

PANEL L

Nominal 208.0 V 3P 3467.18 A

SLG 2375.38 A

SERVICE DISCONNECT

Sensor/Trip 200.0 A Plug 200.0 A

CBL- DISC TO MDP

Size 3/0 AWG 1 Runs/Phase Insulation XLPE Class TECK90 Raceway Magnetic Length 10.0 ft

CBM MDP

Sensor/Trip 225.0 A Plug 225.0 A

MAIN DISC

Nominal 208.0 V 3P 5551.44 A

SLG 3562.46 A

JBER, Alaska Task Order # 0001

Appendix D

Overcurrent Device Coordination Analysis

Existing Settings

SIEMENS

QJ

QJ

Trip 150.0 A Plug 150.0 A Settings Phase Thermal Curve (Fixed) INST Fixed (1275A)

CB PANEL P

CUTLER-HAMMER

CA

CA

Trip 200.0 A Plug 200.0 A Settings Phase Fixed

SERVICE DISCONNECT

SIEMENS

QJ

QJ

Trip 225.0 A Plug 225.0 A Settings Phase Thermal Curve (Fixed) INST Fixed (1500A)

CBM MDP

SIEMENS

QJ

QJ

Trip 150.0 A Plug 150.0 A Settings Phase Thermal Curve (Fixed) INST Fixed (1275A)

CB PANEL P

CUTLER-HAMMER

CA

CA

Trip 200.0 A Plug 200.0 A Settings Phase Fixed

SERVICE DISCONNECT

SIEMENS

QJ

QJ

Trip 225.0 A Plug 225.0 A Settings Phase Thermal Curve (Fixed) INST Fixed (1500A)

CBM MDP

UTILITY

SP

T UTILITY #88,89,90

T-PRIMARY

T SECONDARY CBL-SECONDARY

MDP

CB PANEL P

CBL-PANEL P

CBL-PANEL L

PANEL P

PANEL L

SERVICE DISCONNECT

CBL- DISC TO MDP

CBM MDP

MAIN DISC

TCC: 2212 TCC AS-IS 09-19 Current Scale x 1 Reference Voltage: 208 September 19, 2018

Oct 05, 2018 07:44:35 Page 1

Project Name: 2212

TCC Name: 2212 TCC EXISTING.tcc

Reference Voltage: 208 V

Current Scale: X 10^0

TCC Notes:

TCC Comment:

Fault Duty Option: Study Result - Bus Fault Current

ALL INFORMATION PRESENTED IS FOR REVIEW, APPROVAL, INTERPRETATION,

AND APPLICATION BY A REGISTERED ENGINEER ONLY.

SKM DISCLAIMS ANY RESPONSIBILITY AND LIABILITY RESULTING

FROM THE USE AND INTERPRETATION OF THIS SOFTWARE.

CAPTOR (Computer Aided Plotting for Time Overcurrent Reporting)

COPYRIGHT SKM SYSTEMS ANALYSIS, INC. 1983-2018

Device Name: CB PANEL P TCC Name: 2212 TCC EXISTING.tcc

Bus Name: MDP Bus Voltage: 208.0V

Function Name: Phase

Manufacturer: SIEMENS

Description: 125-225A

Type: QJ

AIC Rating: 10kA Fault Duty: 5366.6A

Frame: QJ 240V 150A Tcc Current Multiplier: 1

Tcc Time Multiplier: 1 Tcc Time Adder: 0

Trip: 150A

Setting: 1) Thermal Curve (Fixed

2) INST Fixed (1275A)

Device Name: SERVICE DISCONNECT TCC Name: 2212 TCC EXISTING.tcc

Bus Name: MAIN DISC Bus Voltage: 208.0V

Function Name: Phase

Manufacturer: CUTLER-HAMMER

Description: 125-225A

Type: CA

AIC Rating: 10kA Fault Duty: 5551.4A

Frame: CA 240V 225A Tcc Current Multiplier: 1

Tcc Time Multiplier: 1 Tcc Time Adder: 0

Trip: 200A

Setting: 1) Fixed

Oct 05, 2018 07:44:35 Page 2

Device Name: CBM MDP TCC Name: 2212 TCC EXISTING.tcc

Bus Name: MDP Bus Voltage: 208.0V

Function Name: Phase

Manufacturer: SIEMENS

Description: 125-225A

Type: QJ

AIC Rating: 10kA Fault Duty: 5366.6A

Frame: QJ 240V 225A Tcc Current Multiplier: 1

Tcc Time Multiplier: 1 Tcc Time Adder: 0

Trip: 225A

2) INST Fixed (1500A)

JBER, Alaska Task Order # 0001

Appendix E

Overcurrent Device Coordination Analysis

Recommended Settings

0.5 1 10 1

K

K

0.01

0.10

CURRENT IN AMPERES

T I M E

I N

S E C O N D S

SIEMENS

QJ

QJ

Trip 225.0 A

Plug 225.0 A

Settings Phase

Thermal Curve (Fixed)

INST Fixed (1500A)

CBM MDP

SIEMENS

QJ2

QJ2

Trip 100.0 A

Plug 100.0 A

Settings Phase

Thermal Curve (Fixed)

INST Fixed (900A)

CB PANEL P

CUTLER-HAMMER

CA

CA

Trip 200.0 A

Plug 200.0 A

Settings Phase

Fixed

SERVICE DISCONNECT

SIEMENS

QJ

QJ

Trip 225.0 A

Plug 225.0 A

Settings Phase

Thermal Curve (Fixed)

INST Fixed (1500A)

CBM MDP

SIEMENS

QJ2

QJ2

Trip 100.0 A

Plug 100.0 A

Settings Phase

Thermal Curve (Fixed)

INST Fixed (900A)

CB PANEL P

CUTLER-HAMMER

CA

CA

Trip 200.0 A

Plug 200.0 A

Settings Phase

Fixed

SERVICE DISCONNECT

UTILITY

SP

T UTILITY #88,89,91

CBL-SECONDARY

MDP

CB PANEL P

CBL-PANEL P

CBL-PANEL L

PANEL P

PANEL L

SERVICE DISCONNECT

CBL- DISC TO MDP

CBM MDP

T-PRIMARY

T SECONDARY1

MAIN DISCONNECT

TCC: 2212 TCC RECOMMENDATION Current Scale x 1 Reference Voltage: 208 October 4, 2018

Oct 05, 2018 10:14:33 Page 1

Project Name: 2212 RECOMMENDED

TCC Name: 2212 TCC RECOMMENDATION.tcc

R…