Arc-Flash Study
Remake batch 25 and its neighbor re-points, batch 24 where missing, and the adopted-electrical-code parameter: brought in line with the authoring repository
Showing changes from Rev 6
to Rev 7
in Arc-Flash Study.
---
−title: Arc-Flash Hazard Analysis
+title: Arc-Flash Study
category: Electrical / Power Studies
−toc_depth: 3
description: >
− When to use: Engineering analysis to calculate incident energy and the arc-flash boundary at every piece of electrical equipment where workers may interact with the equipment while it is energized or while it could be placed into an electrically safe work condition. Applies to AC systems from 208V through medium voltage, in commercial, institutional, industrial, and healthcare facilities. The study produces equipment labels, PPE specifications, and the documentation that supports an NFPA 70E-compliant electrical safety program.
− Not intended for: Short-circuit analysis on its own (see [[sync/short-circuit-study]]), protective device coordination on its own (see [[sync/protective-coordination-study]]), DC system arc-flash analysis (covered by NFPA 70E Article 130.5 informational annexes rather than IEEE 1584), arc-flash analysis of utility-owned equipment upstream of the service point, or development of the site's electrical safety work practices program itself (the study is an input to the program, not a substitute for it).
+ When to use: The arc-flash study for a project's electrical power distribution system: the incident energy and the arc-flash boundary at every bus a worker examines, adjusts, services, or maintains while it is energized, on AC systems from 208 V through 38 kV with utility, generator, inverter-based, and paralleled sources, and on the DC side of battery, energy storage, and photovoltaic equipment where the project includes it. Covers who performs the study and when it is issued, the IEEE 1584-2018 method and the methods applied outside its range, the buses studied, the source operating cases and the maintenance-mode cases, the arcing current variation, the clearing time taken from the accepted coordination settings, the arc-flash input data the system model does not already carry (electrode configuration, enclosure dimensions, bus gap, working distance), the content of the arc-flash label, the PPE arc rating the facility's safety program consumes, the mitigation recommendations, the report, and the five-year review and the events that call for a re-study.
+
+ Not intended for: the bolted fault current, the X/R, and the system model that produce it ([[sync/short-circuit-study]]); the settings of the protective devices and their time-current selectivity ([[sync/protective-coordination-study]]); the tag as a manufactured product, its material, its attachment, and where it is placed on the equipment ([[sync/equipment-labeling]]); the facility's written procedures for energized work, its permits, and the training of qualified persons ([[sync/electrical-safety-program]]); the field verification of the installed trip and relay values before energization ([[sync/electrical-acceptance-testing]]); arc-resistant construction and arc energy reduction as switchgear features ([[sync/low-voltage-switchgear]], [[sync/medium-voltage-switchgear]]); and equipment on the utility's side of the point of delivery.
---
# Scope {toc}
−## This specification covers the engineering analysis required to determine the incident energy exposure and arc-flash boundary at each location in an electrical power system where a worker may interact with energized equipment, and to produce the equipment labels and the supporting documentation required by NFPA 70E and NFPA 70 (NEC).
+## This standard governs the arc-flash study as an engineering deliverable: the engineer who performs it and when it is issued, the calculation method, the buses studied, the cases, the inputs the study adds to the system model it inherits, the clearing time it takes from the coordination settings, the content of the label at each bus, the PPE arc rating it hands to the facility's safety program, the mitigation it recommends, the report, and the review cycle that keeps the labels true. {note}
−## The analysis shall be performed using the calculation methodology of IEEE 1584, current edition, supplemented for conditions outside the IEEE 1584 model range by methods identified in NFPA 70E Annex D.
+## NFPA 70E 130.5 requires an arc flash risk assessment for every task a worker performs on energized equipment, and NFPA 70 110.16 requires the equipment likely to be worked on energized to carry a label that warns of the hazard; 110.16(B) adds, for service and feeder equipment rated 1200 A and more, the incident energy or the arc rating the worker needs. OSHA 29 CFR 1910.333 and 1910.335 require the employer to protect the worker from the hazard the equipment presents. None of these can be met from a nameplate; each rests on the incident energy at the bus, and this study is that calculation. {note}
−## An arc-flash hazard analysis is not a stand-alone study because incident energy at any bus depends on both the arcing current at that bus (a short-circuit problem) and on the clearing time of the protective device upstream (a coordination problem). {note}
+## The arc-flash study is the last of three studies performed on one system model. The short-circuit study under [[sync/short-circuit-study]] gives the bolted fault current at every bus, the coordination study under [[sync/protective-coordination-study]] fixes the settings that decide how long the arc burns, and this study turns the two into incident energy, an arc-flash boundary, and a label. A change to either predecessor moves every result here, which is why this study is not started until the coordination settings are accepted and is re-run whenever they change. {note}
−## The arc-flash study shall be performed only after the short-circuit study per [[sync/short-circuit-study]] and the protective device coordination study per [[sync/protective-coordination-study]] are complete and the protective device settings are finalized.
+## The following are governed elsewhere and are outside this standard: {note}
−## The arc-flash calculation shall not be re-run with assumed device settings and reconciled later, because an arc-flash label is only valid when the device that clears the arc has been set to the values used in the calculation.
+- the bolted fault currents, the X/R ratios, the utility's contribution, the transformer, conductor, and machine impedances, the source operating configurations, and the survey of existing equipment that feeds the model, under [[sync/short-circuit-study]], which hands this study its model and its results
+- the protective device settings and the clearing times they produce, under [[sync/protective-coordination-study]], which this study reads and does not change
+- the arc-flash label as a physical product, its material, its lettering, its attachment, and its location on each item of equipment, under [[sync/equipment-labeling]]; this study supplies every value printed on it
+- the facility's written electrical safety program, the energized work permit, the task-level risk assessment, the shock protection boundaries as work rules, the training of qualified persons, and the procurement of PPE, under [[sync/electrical-safety-program]], which consumes the incident energy, the boundaries, and the arc ratings this study reports
+- the field verification that each trip unit and relay is set to the accepted settings, under [[sync/electrical-acceptance-testing]], whose as-left settings record this study is confirmed against
+- the arc energy reduction NFPA 70 240.67 and 240.87 require, the maintenance switch, the zone-selective interlocking, and the arc-resistant construction, as features the equipment is ordered with, under [[sync/low-voltage-switchgear]], [[sync/low-voltage-switchboards]], [[sync/medium-voltage-switchgear]], and the other equipment standards; this study calculates their effect and recommends them where they pay
+- the arc-flash warning on each item of equipment and the operating state its label states, which each equipment standard requires and this study supplies the values for, under [[sync/panelboards]], [[sync/motor-control-centers]], [[sync/busway]], [[sync/automatic-transfer-switches]], [[sync/generator-paralleling-switchgear]], [[sync/secondary-unit-substations]], [[sync/electrical-service-entrance]], [[sync/generators]], [[sync/industrial-control-panels]], [[sync/battery-energy-storage-systems]], [[sync/uninterruptible-power-supply-systems]], and [[sync/dc-battery-systems]]
+- equipment on the utility's side of the point of delivery, and the arc-flash practices of the utility's own workers under OSHA 29 CFR 1910.269
−## The study deliverable is twofold: a calculation report documenting the system model, input data, methodology, and bus-by-bus results, and a set of physical labels installed on the equipment. {note}
+## The study shall calculate the incident energy and the arc-flash boundary at every bus within the study boundary described under Buses Studied, in every operating case and maintenance-mode case this standard requires, with the clearing time taken from the coordination settings accepted under [[sync/protective-coordination-study]].
−## The study shall produce a calculation report that documents the system model, the input data, the methodology, and the results bus-by-bus.
−
−## The study shall produce a set of physical labels installed on the equipment so that a worker about to open a door or remove a cover can read, in front of the equipment, the incident energy at the working distance, the arc-flash boundary, the nominal voltage, and the PPE required to perform the intended task.
−
−## Both the calculation report and the physical labels are required; neither substitutes for the other.
−
−## This standard does not establish the site's electrical safety program; it produces the technical inputs that the safety program relies on. {note}
−
−## The Owner remains responsible for adopting NFPA 70E (or an equivalent standard), training qualified workers, establishing energized-work permitting, providing and maintaining PPE, and reviewing the analysis on the schedule required by NFPA 70E.
−
−## Work practices and training shall be coordinated with [[sync/electrical-safety-program]].
−
−## Equipment scope shall be coordinated with [[sync/low-voltage-switchgear]], [[sync/medium-voltage-switchgear]], [[sync/low-voltage-switchboards]], [[sync/panelboards]], [[sync/motor-control-centers]], [[sync/low-voltage-dry-type-transformers]], and [[sync/medium-voltage-transformers]].
−
−## The arc-flash study shall include every piece of equipment specified by the coordinated equipment standards that is within the analysis voltage threshold.
−
# Referenced Standards {toc}
−## Analysis, labeling, and documentation shall comply with the latest adopted edition of the following standards and codes.
+## The study, its model, and its report shall comply with the latest adopted edition of each of the following unless a specific edition is cited.
+## Where the contract documents, the adopted edition of NFPA 70, the Owner's electrical safety program, or two referenced standards impose conflicting requirements, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
+
| Standard | Title |
|----------|-------|
−| IEEE 1584 | Guide for Performing Arc-Flash Hazard Calculations |
+| IEEE 1584-2018 | Guide for Performing Arc-Flash Hazard Calculations |
| IEEE 1584.1 | Guide for the Specification of Scope and Deliverable Requirements for an Arc-Flash Hazard Calculation Study in Accordance with IEEE Std 1584 |
−| NFPA 70 | National Electrical Code (Articles 110.16, 130.5, 240.87) |
−| NFPA 70E | Standard for Electrical Safety in the Workplace |
−| OSHA 29 CFR 1910.269 | Electric Power Generation, Transmission, and Distribution |
−| OSHA 29 CFR 1910.333 | Selection and Use of Work Practices |
−| OSHA 29 CFR 1910.335 | Safeguards for Personnel Protection |
+| NFPA 70 | National Electrical Code (Articles 110.16, 110.24, 240.67, 240.87, and 409.110) |
+| NFPA 70E | Standard for Electrical Safety in the Workplace (Article 130 and Informative Annex D) |
+| NFPA 70B | Standard for Electrical Equipment Maintenance |
+| OSHA 29 CFR 1910.333 | Selection and Use of Work Practices (Subpart S, Electrical) |
+| OSHA 29 CFR 1910.335 | Safeguards for Personnel Protection (Subpart S, Electrical) |
| IEEE 551 | Recommended Practice for Calculating AC Short-Circuit Currents in Industrial and Commercial Power Systems (Violet Book) |
−| ANSI/IEEE C37.010 | Application Guide for AC High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis |
−| ANSI/IEEE C37.13 | Low-Voltage AC Power Circuit Breakers Used in Enclosures |
| IEEE 242 | Recommended Practice for Protection and Coordination of Industrial and Commercial Power Systems (Buff Book) |
+| IEEE C37.010 | Application Guide for AC High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis |
+| IEEE C37.13 | Low-Voltage AC Power Circuit Breakers Used in Enclosures |
+| IEEE C37.20.7 | Guide for Testing Switchgear Rated Up to 52 kV for Internal Arcing Faults |
+| UL 489 | Molded-Case Circuit Breakers, Molded-Case Switches, and Circuit-Breaker Enclosures |
+| UL 248 | Low-Voltage Fuses |
| ANSI Z535.4 | Product Safety Signs and Labels |
−| UL 969 | Marking and Labeling Systems |
+| ASTM F1506 | Standard Performance Specification for Flame Resistant and Electric Arc Rated Protective Clothing Worn by Workers Exposed to Flames and Electric Arcs |
−## Where the contract documents, the adopted edition of NFPA 70, or a referenced standard conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
−
−## NFPA 70E is the dominant authority for the worker-facing portion of the analysis (PPE, boundaries, labels, work practices), IEEE 1584 is the dominant authority for the calculation methodology, and OSHA 29 CFR Subpart S references both and is the enforceable federal requirement in the United States. {note}
−
# Submittals {toc}
## Action Submittals {toc}
−### Contractor or the Engineer of Record shall submit the following for review prior to performing the analysis, so that disagreements over scope do not surface only after the report is delivered:
+### The Contractor shall submit the following for review by the Engineer of Record:
−- Qualifications of the analyst, including degree, professional engineering registration, and a record of comparable completed studies
−- Identification of the calculation software, version, and the IEEE 1584 model edition the software implements
−- A scope statement listing every bus, switchboard, panelboard, motor control center, switchgear lineup, transformer, and other equipment to be included, and explicit identification of any equipment excluded from the study with justification
−- A list of source data the analyst will rely on, including utility short-circuit data, equipment nameplates, conductor sizes and lengths, and protective device settings
−- A field-survey plan for any data that must be collected on site
−- A draft single-line diagram showing the level of detail to be modeled, including where the model terminates at downstream branches
−- A proposed label format compliant with NFPA 70E 130.5(H) and any Owner-specific label requirements
−- A schedule milestone for delivery of the calculation report, draft labels, and final labels
+- the qualifications of the study engineer, giving the license, the firm, and the comparable studies described under Study Engineer
+- the study plan, giving the calculation method, the analysis software and its version, the buses to be studied as a preliminary one-line diagram carrying the bus identifiers the labels will use, the source operating cases and maintenance-mode cases to be run, the basis for the electrode configuration, enclosure dimensions, bus gap, and working distance at each equipment class, the method to be applied at any bus outside the IEEE 1584-2018 range, and the schedule of each issue against the acceptance of the coordination study and the energization date
+- a statement that the coordination study under [[sync/protective-coordination-study]] has been accepted, naming its revision, before the final issue is prepared
+- the study report described under Study Report, at each issue the datasheet selects under Study Issues
+- the label schedule described under Label Schedule, for the final issue
```datasheet
−label: Action Submittals Required
+label: Action Submittals
type: checkbox
options:
− - "Analyst qualifications and PE registration"
− - "Calculation software identification and version"
− - "Study scope statement (included / excluded equipment)"
− - "Source data list and field-survey plan"
− - "Draft single-line diagram for modeling"
− - "Proposed label format and content"
− - "Delivery schedule"
−default: "Analyst qualifications and PE registration"
+ - "Study engineer qualifications"
+ - "Study plan with preliminary one-line diagram"
+ - "Coordination study acceptance statement"
+ - "Study report at each issue"
+ - "Label schedule"
+default:
+ - "Study engineer qualifications"
+ - "Study plan with preliminary one-line diagram"
+ - "Coordination study acceptance statement"
+ - "Study report at each issue"
+ - "Label schedule"
+constraint: all_of
```
+### The study plan shall be reviewed and returned before the arc-flash calculation is run, and the final report shall not be submitted until the plan covering it has been returned.
+
+### The study plan settles, before any case is run, the questions that otherwise surface when the labels are already printed: which buses are in and which are out, which operating states the worker will meet, whether the enclosure sizes are typical or measured, and whether the study will be back before the equipment is energized. A plan returned with the boundary drawn and the cases named is what makes the labels a record of the system rather than a best guess at it. {note}
+
## Closeout Submittals {toc}
−### Contractor shall provide the following at substantial completion, delivered in a form that can be re-opened and edited when the study is updated:
+### The Contractor shall submit the following before the equipment within the study boundary is energized:
−- Final arc-flash calculation report, sealed by a registered professional engineer
−- Native calculation-software project file (not only a PDF export) so that future updates can be performed without rebuilding the model
−- Final single-line diagram with bus identifiers matching the report and the labels
−- Bus-by-bus results table including bolted-fault current, arcing current, arc duration, working distance, incident energy at the working distance, arc-flash boundary, and the required PPE category or arc-rating
−- A copy of each installed label with its corresponding bus identifier
−- Photographs of installed labels on each piece of equipment
−- A statement of the date of the study, the protective device settings the calculation assumed, and the utility fault current the calculation assumed
+- the final study report, confirmed against the as-left settings record of [[sync/electrical-acceptance-testing]] where the datasheet selects a confirmation under Study Issues, and otherwise re-issued with a reconciliation of the settings used against the settings accepted
+- the native model files of the analysis software, with the software version and device library revision that produced the report
+- the final label schedule, as the record of every value printed on every arc-flash label
+- the PPE arc rating table described under PPE Arc Rating, written for the Owner's electrical safety program
+- the re-study trigger list described under Review and Re-Study Triggers, written for the Owner's operations staff
```datasheet
−label: Closeout Submittals Required
+label: Closeout Submittals
type: checkbox
options:
− - "Final sealed arc-flash calculation report"
− - "Native calculation-software project file"
− - "Final single-line diagram with matching bus identifiers"
− - "Bus-by-bus results table"
− - "Copy of each installed label with bus identifier"
− - "Photographs of installed labels"
− - "Statement of study date and assumed settings / fault current"
−default: [Final sealed arc-flash calculation report, Native calculation-software project file, Final single-line diagram with matching bus identifiers, Bus-by-bus results table, Copy of each installed label with bus identifier, Photographs of installed labels, Statement of study date and assumed settings / fault current]
+ - "Final study report confirmed against the as-left settings"
+ - "Native model files with software version and library revision"
+ - "Final label schedule"
+ - "PPE arc rating table"
+ - "Re-study trigger list"
+default:
+ - "Final study report confirmed against the as-left settings"
+ - "Native model files with software version and library revision"
+ - "Final label schedule"
+ - "PPE arc rating table"
+ - "Re-study trigger list"
+constraint: all_of
```
+### The native model files shall be delivered in a form the Owner can open and edit with a licensed copy of the software, without a password, a locked library, or a dependency on the study engineer's account.
+
+### The label on the door is read for the life of the equipment, and the five-year review and every re-study open the model that produced it. A review that has to rebuild the model from the PDF re-enters every enclosure size, gap, and working distance by hand, and a value that drifts in the re-entry prints on a new label as a fact. {note}
+
# Quality Assurance {toc}
−## Analyst Qualifications {toc}
+## Study Engineer {toc}
+### The study shall be performed by the study engineer indicated in the datasheet.
+
```datasheet
−label: Analyst Relationship to Design Team
−type: radio
+label: Study Engineer
+type: select
options:
− - "Engineer of Record performs the study"
− - "Independent third-party engineer performs the study"
− - "Manufacturer-provided study (subject to independent review)"
−default: "Independent third-party engineer performs the study"
+ - "Engineer performing the short-circuit and coordination studies"
+ - "Engineer of Record"
+ - "Independent engineer engaged by the Contractor"
+ - "Equipment manufacturer's engineering services"
+ - "Testing organization's engineering group"
+default: "Engineer performing the short-circuit and coordination studies"
```
−### The arc-flash analysis shall be performed under the responsible charge of a registered professional engineer with documented experience performing arc-flash studies to IEEE 1584.
+### The engineer who performed the short-circuit and coordination studies already holds the model, the assumption register, and the settings the arc-flash calculation reads, and runs the arc-flash study as a third pass on the same file, which is why that arrangement is the one on nearly every project; the other four arrangements are the ones the short-circuit study offers for its own engineer, with the same trade-offs recorded under [[sync/short-circuit-study]], and a project selects one of them here where the arc-flash study is procured separately, as when an Owner engages an independent engineer to label an existing facility whose studies were performed by others. {note}
−### The analyst shall have completed a minimum of five comparable studies for facilities of similar size and voltage class.
+### The study shall be performed under the responsible charge of a Professional Engineer licensed in the jurisdiction of the project, and the report, the one-line diagram, the results tables, and the label schedule shall bear that engineer's seal and signature.
−### The analyst shall be familiar with both the calculation methodology and the practical realities of field data collection.
+### The study engineer shall have performed not fewer than five arc-flash studies to IEEE 1584-2018 on systems of the same voltage class and of comparable size within the five years before the study, and shall name them in the qualifications.
−### The analyst is not required to be the same engineer who designed the electrical system; an independent analyst brings fresh eyes while the designer of record has the most complete knowledge of the system, and either is acceptable provided the qualifications are met. {note}
+### Where the study engineer is not the engineer who performed the coordination study, the study shall be built on the accepted short-circuit model handed over under [[sync/short-circuit-study]] and on the accepted settings of [[sync/protective-coordination-study]], and the study engineer shall report every departure from either to the Engineer of Record before the final issue.
−### A manufacturer-provided study is acceptable only where the manufacturer also models the upstream utility source and the downstream branches that affect arcing current.
+### Where the equipment manufacturer's engineering services perform the study, the model shall include every source, bus, and protective device within the study boundary, whether or not the manufacturer furnished it, and a study limited to the manufacturer's own equipment shall not be accepted.
−### A study limited to the manufacturer's own equipment lineup is not a complete facility study.
+### Where the study engineer is not the Engineer of Record, the Engineer of Record shall review the study report and return it before any label is printed from it.
−## Calculation Software {toc}
+### Where the study engineer and the Engineer of Record disagree on an input value, an assumption, or the treatment of a bus, the Engineer of Record shall make the determination and the study shall record it in the assumption register.
+## Study Issues {toc}
+
+### The study shall be issued at each point in the project indicated in the datasheet.
+
```datasheet
−label: IEEE 1584 Calculation Edition
−type: radio
+label: Study Issues
+type: checkbox
options:
− - "IEEE 1584-2018 (current edition)"
− - "IEEE 1584-2002 with 2004a amendment (legacy)"
−default: "IEEE 1584-2018 (current edition)"
+ - "Preliminary issue on design data before equipment release"
+ - "Final issue on the accepted coordination settings before energization"
+ - "Confirmation against the as-left settings record after acceptance testing"
+default:
+ - "Final issue on the accepted coordination settings before energization"
+ - "Confirmation against the as-left settings record after acceptance testing"
+constraint: all_of
```
−### The analysis shall be performed in a software package that implements the IEEE 1584 calculation method to the edition specified in this standard.
+### A preliminary issue on design data and preliminary settings is run while the equipment can still change, and it is the issue that decides whether a main section needs arc-resistant construction, a maintenance switch, or a faster upstream fuse before the switchgear is ordered; the final issue on the accepted coordination settings is the one every label is printed from; the confirmation against the as-left settings record compares the settings the study used with the settings the testing organization recorded at each device, re-runs the buses where they differ, and is the step that keeps a trip unit left at its shipping setting from invalidating a label that says otherwise. {note}
−### Hand calculations and spreadsheet implementations are not acceptable for a facility study.
+### The final issue shall not be run until the coordination study under [[sync/protective-coordination-study]] has been accepted in writing, and a preliminary issue shall state on its cover and on every results table that its values are not to be printed on a label.
−### The IEEE 1584-2018 model has more than thirty equations selected and weighted by voltage range and electrode configuration, and propagating an error through a spreadsheet is too easy. {note}
+### Where a confirmation is selected, the study engineer shall compare the setting of every device in the model against the as-left settings record delivered under [[sync/electrical-acceptance-testing]], shall re-run every bus whose clearing device differs, and shall re-issue the report and the label schedule for those buses before the equipment is energized.
−### The 2018 edition shall be used for new studies.
+### Where a confirmation is not selected, the Contractor shall deliver the as-left settings record to the Engineer of Record with the closeout submittals, and the Engineer of Record shall direct a re-run of any bus whose clearing device is found set other than the study assumed.
−### Where an existing site has a 2002-edition study on file, the next periodic review shall convert the study to the 2018 model rather than continuing to update under the superseded edition.
+### No arc-flash label shall be printed from a preliminary issue, from a study run on settings that have not been accepted, or from a study whose model has been superseded under [[sync/short-circuit-study]].
−### The 2002 edition's two-equation model has been replaced by a substantially different model that incorporates electrode configuration, enclosure size, and a broader empirical test database, and is identified here only so that a legacy study can be recognized on inspection. {note}
+### An arc-flash label is a statement about one device: that it will clear an arcing fault in the time the study read from its curve. A device set to a different value clears in a different time, and the label on the door is then wrong by a factor the worker cannot see. The sequence, settings accepted, settings applied, settings recorded, study confirmed, labels printed, is what makes the number on the door the number in the room. {note}
−### The 2002 model shall not be the basis of a new analysis.
+## Calculation Tool {toc}
−# Methodology {toc}
+### The study shall be performed with the calculation tool indicated in the datasheet.
−## IEEE 1584-2018 Model {toc}
+```datasheet
+label: Calculation Tool
+type: radio
+options:
+ - "Commercial power system analysis software on the model handed over from the short-circuit and coordination studies"
+ - "Independent calculation of the IEEE 1584-2018 equations from the accepted short-circuit and coordination reports"
+default: "Commercial power system analysis software on the model handed over from the short-circuit and coordination studies"
+```
−### The IEEE 1584-2018 model calculates the arcing current, the arc duration, the incident energy at a working distance, and the arc-flash boundary as a function of bolted-fault current, system voltage, electrode configuration, enclosure dimensions, electrode gap, and working distance. {note}
−### The model is empirical and is valid only within the range of conditions from which it was derived. {note}
+### Commercial analysis software reads the arcing current off the device curve, applies the arcing current variation and the enclosure size correction of IEEE 1584-2018 at every bus without transcription, and keeps the arc-flash results in the same file the next re-study opens, which is why it is the tool on nearly every study; an independent calculation of the IEEE 1584-2018 equations, in a spreadsheet or by hand from the bolted fault currents and the clearing times tabulated in the two accepted reports, is reproducible by any engineer with those reports and is the tool a project accepts where the system is a single service with a handful of buses and the short-circuit study was itself a hand calculation, with the result that there is no model file to hand to the next review. {note}
−### For conditions outside the model range — for example, voltages below 208V, single-phase systems, DC systems, or open-air arcs in configurations not tested — alternative methods from NFPA 70E Annex D shall be applied and identified in the report.
+### Where software is selected, the report shall identify the software, its version, and the revision of the device library used, and the Contractor shall not name the software in the study plan as a condition of the work.
−### The voltage range of the 2018 model is 208V to 15kV. {note}
+### Where software is selected, the study engineer shall verify the software result by an independent calculation of the IEEE 1584-2018 equations at the service equipment and at one bus on the secondary of each transformer class in the system, and shall include the verification in the report.
−### The bolted-fault-current range is 500A to 106kA for low-voltage equipment and 200A to 65kA for medium-voltage equipment. {note}
+### Where an independent calculation is selected, the report shall show at every bus the bolted fault current, the arcing current and its reduced value, the clearing time read at each, the intermediate values of the IEEE 1584-2018 equations, the enclosure size correction factor, and the incident energy and arc-flash boundary that result, so that every value can be reproduced from the report alone.
−### The electrode gap range is 6mm to 76mm (0.25 in. to 3 in.) for low voltage and 19mm to 254mm (0.75 in. to 10 in.) for medium voltage. {note}
+# Calculation Basis {toc}
−### The analyst shall confirm that every bus modeled lies within the model's voltage, bolted-fault-current, and electrode-gap ranges.
+## IEEE 1584-2018 Model {toc}
−### The analyst shall document the alternative method used for any bus that does not lie within the model's ranges.
+### The incident energy and the arc-flash boundary at every three-phase AC bus within the range of the IEEE 1584-2018 model shall be calculated by that model, with the electrode configuration, enclosure dimensions, bus gap, and working distance for the bus as established under Arc-Flash Input Data.
−## Electrode Configuration {toc}
+### The IEEE 1584-2018 model is empirical, built from a test program that spanned three-phase systems from 208 V through 15 kV, bolted fault currents from 500 A to 106 kA at 600 V and below and from 200 A to 65 kA above 600 V, electrode gaps from 6.35 mm to 76.2 mm at low voltage and from 19.05 mm to 254 mm at medium voltage, working distances of 305 mm and more, and five electrode configurations. Within that range it predicts the arcing current, the incident energy, and the arc-flash boundary from the bolted fault current, the voltage, the gap, the enclosure, the configuration, the working distance, and the arc duration; outside it, the equations are extrapolating from data they were never fitted to, which is why the study has to know, bus by bus, which side of the range it is on. {note}
−### IEEE 1584-2018 introduced explicit electrode configuration as an input to the calculation. {note}
−### The five configurations and their typical application are: {note}
+### The study engineer shall confirm, for every bus, that the voltage, the bolted fault current, and the gap lie within the IEEE 1584-2018 range, and the results tables shall identify every bus that does not.
−| Configuration | Description | Typical Application |
−|---------------|-------------|---------------------|
−| VCB | Vertical electrodes inside a metal box enclosure | Most LV switchgear and switchboards |
−| VCBB | Vertical electrodes terminated in an insulating barrier inside a metal box | LV equipment with barrier between bus and cable compartment |
−| HCB | Horizontal electrodes inside a metal box enclosure | Some LV switchgear designs; many MV configurations |
−| VOA | Vertical electrodes in open air | Open-frame substations, exposed bus, cable terminations in open air |
−| HOA | Horizontal electrodes in open air | Open-frame substations with horizontal bus |
+### The model of IEEE 1584-2002, with its single arcing current and its exemption for circuits below 240 V, shall not be the basis of a new study or of a review, and a facility whose study on file was performed under the 2002 edition shall have it converted to the 2018 model at its next review.
−### For identical electrical conditions, electrode configuration alone can change the calculated incident energy by a factor of four or more, and selecting VCBB for every bus inflates incident energy uniformly, masks the equipment where mitigation would pay off, and drives unnecessary PPE category increases. {note}
+## Buses Outside the Model Range {toc}
−### The analyst shall select the electrode configuration that matches the actual equipment construction, not the most conservative configuration as a default.
+### At every bus outside the range of the IEEE 1584-2018 model, the incident energy and the arc-flash boundary shall be established by the method indicated in the datasheet.
```datasheet
−label: Electrode Configuration Selection Basis
−type: radio
+label: Method for Buses Outside the IEEE 1584-2018 Range
+type: select
options:
− - "Per equipment construction (specific configuration for each bus)"
− - "Conservative default (VCBB for all LV, HCB for all MV)"
−default: "Per equipment construction (specific configuration for each bus)"
+ - "Ralph Lee method of NFPA 70E Informative Annex D.2"
+ - "IEEE 1584-2018 model extended to the bus by documented engineering judgment"
+ - "No incident energy calculated and the bus labeled to be de-energized before work"
+default: "Ralph Lee method of NFPA 70E Informative Annex D.2"
```
−### The electrode configuration shall be documented in the bus-by-bus results table.
+### The Ralph Lee method is a theoretical open-air calculation that overstates the incident energy at most buses, is the method the analysis software applies above 15 kV and on single-phase systems as a matter of course, and gives a conservative label at the cost of a conservative PPE requirement; extending the IEEE 1584-2018 model by judgment, as where a gap or a fault current lies just past the tested range, gives a realistic value at the cost of an assumption that the register has to carry and the reviewer has to accept; calculating nothing and labeling the bus to be de-energized before any work is the arrangement for a bus no one will ever open energized, as an outdoor transformer primary compartment, and it leaves the worker no number where the bus is opened anyway. The buses that commonly fall outside the range are the utility primary above 15 kV, single-phase equipment, and 208 V buses with a bolted fault current below 500 A. {note}
−## Maximum and Minimum Arcing Current {toc}
+### The method applied at each bus outside the range shall be named in the results tables beside that bus, and the assumption register shall record the input that places the bus outside the range.
−### The analysis shall be performed at both the maximum and the minimum arcing current at each bus.
+## Equipment Rated 240 V and Below {toc}
−### Maximum arcing current produces the worst-case incident energy when the upstream device trips on its instantaneous element, while minimum arcing current — a 0.85 multiplier for low voltage and 0.96 for medium voltage — is the lower-bound case in which the upstream device may clear on a longer time-delay band and the arc burns longer. {note}
+### Every bus rated 240 V and below within the study boundary shall be calculated, whatever the kVA of the transformer that serves it, and the report shall not exempt a bus on the basis of transformer size.
−### The reported value at each bus shall be the higher of the maximum-arcing-current and minimum-arcing-current results.
+### IEEE 1584-2002 permitted a study to leave out circuits below 240 V fed by a single transformer under 125 kVA, and a generation of studies and labels was built on that exemption. IEEE 1584-2018 withdrew it. The 2018 edition notes only that a sustained arc is less likely on a three-phase system at 240 V and below where the bolted fault current is below 2000 A, and that note is a statement about the likelihood of an arc, not an exemption from calculating its energy. The 208 V panelboard on a 75 kVA transformer is the bus a maintenance electrician opens most often, and it is calculated and labeled like every other. {note}
−### A 2018-edition study that does not show both the maximum and minimum arcing-current values in the bus-by-bus results has not been performed correctly.
+### Where a bus rated 240 V and below has a bolted fault current below 2000 A, the results tables shall state the bolted fault current beside the result, and the label shall carry the calculated incident energy.
−### The dual maximum/minimum calculation is a frequent point of error in legacy 2002-edition studies, which used a single arcing-current value. {note}
+## DC Arc-Flash {toc}
−## Arc Duration {toc}
+### The incident energy and the arc-flash boundary on the DC side of every battery, energy storage, photovoltaic, and rectifier system rated 100 V DC and more within the study boundary shall be established by the method indicated in the datasheet.
−### Arc duration is the time from arc initiation to the moment the upstream device interrupts the current. {note}
−### It is the dominant variable in incident energy: doubling the duration doubles the incident energy. {note}
+```datasheet
+label: DC Arc-Flash Calculation Method
+type: select
+options:
+ - "Maximum power method of NFPA 70E Informative Annex D.5"
+ - "Detailed arc model method of NFPA 70E Informative Annex D.5"
+ - "Not performed, no DC equipment rated 100 V and more within the study boundary"
+```
−### Arc duration shall be determined from the protective device's time-current characteristic at the calculated arcing current, plus the device's interrupting time.
+### The IEEE 1584-2018 model is an AC model and offers nothing for a battery string or a DC bus. The maximum power method of NFPA 70E Informative Annex D.5 takes the arc at the point of maximum power transfer, half the bolted DC fault current at half the system voltage, needs only the bolted fault current and the clearing time, and overstates the energy at every bus, which is the trade a project accepts for a method anyone can check; the detailed arc model method of the same annex calculates the arc resistance from the gap and the current by the published arc models, gives a lower and more realistic energy, and needs a gap for every DC bus and an iteration the software performs. On a project with no DC equipment at or above 100 V, the threshold below which NFPA 70E assigns no DC arc-flash PPE, the question does not arise, and the study states so. {note}
−### For an instantaneous trip, duration is the relay or trip-unit operate time plus the breaker interrupting time, typically 3 to 5 cycles total for low-voltage power circuit breakers and 5 to 8 cycles for medium-voltage breakers.
+### Where a DC method is selected, the DC bolted fault current at each DC bus shall be taken from the battery or energy storage manufacturer's published short-circuit current for the string furnished and from the inverter or rectifier manufacturer's published fault contribution, and the clearing time shall be read from the DC protective device at that current.
−### For a time-delayed trip, duration is the time read off the upstream device's time-current curve at the arcing current.
+### Where a DC method is selected, the study shall report the DC-side and the AC-side result separately for each enclosure that carries both, so that the equipment standard's label can state each, and the DC result shall state that the battery remains energized after the disconnecting means is opened.
−### Where the upstream device does not clear within 2 seconds, NFPA 70E permits the analysis to assume a 2-second maximum on the basis that a worker can typically move out of the arc-flash zone in 2 seconds.
+### Where a DC method is selected, the station battery under [[sync/dc-battery-systems]], the battery of a UPS under [[sync/uninterruptible-power-supply-systems]], the energy storage system under [[sync/battery-energy-storage-systems]], and the DC side of the photovoltaic system under [[sync/photovoltaic-systems]] shall each be included where rated 100 V DC and more.
+# Buses Studied {toc}
+
+## Study Boundary {toc}
+
+### The study shall calculate the incident energy and the arc-flash boundary at every class of equipment indicated in the datasheet within the study boundary, at every item of that class that a worker is likely to examine, adjust, service, or maintain while energized.
+
```datasheet
−label: 2-Second Maximum Arc Duration Cap
−type: radio
+label: Equipment Classes Studied
+type: checkbox
options:
− - "Apply per IEEE 1584 / NFPA 70E (worker can move away)"
− - "Do not apply (use actual device clearing time)"
−default: "Apply per IEEE 1584 / NFPA 70E (worker can move away)"
+ - "Service equipment, switchgear, switchboards, and motor control centers"
+ - "Panelboards"
+ - "Transformer terminal compartments"
+ - "Motor controllers, drives, and disconnect switches"
+ - "Busway tap boxes and plug-in units"
+ - "Transfer switches"
+ - "Generator terminal boxes and paralleling switchgear"
+ - "UPS, energy storage, and photovoltaic inverter output terminals"
+ - "Industrial control panels"
+ - "Meter socket enclosures and current transformer cabinets"
+ - "Junction and pull boxes with splices or terminations"
+default:
+ - "Service equipment, switchgear, switchboards, and motor control centers"
+ - "Panelboards"
+ - "Transformer terminal compartments"
+ - "Motor controllers, drives, and disconnect switches"
+ - "Busway tap boxes and plug-in units"
+ - "Transfer switches"
+ - "Generator terminal boxes and paralleling switchgear"
+ - "UPS, energy storage, and photovoltaic inverter output terminals"
+ - "Industrial control panels"
+ - "Meter socket enclosures and current transformer cabinets"
+constraint: all_of
```
−### The analyst shall document any bus where the 2-second cap is applied and shall flag those locations because the cap is a worker-movement assumption, not a device characteristic.
+### NFPA 70 110.16(A) names the equipment that carries an arc-flash warning, switchboards, switchgear, panelboards, industrial control panels, meter socket enclosures, and motor control centers, and then adds any other equipment likely to be worked on energized, and the list above is that clause written out for the equipment a project actually installs. A transformer terminal compartment and a current transformer cabinet sit on the line side of a main and are among the highest-energy buses in a system; a motor disconnect and a busway plug-in unit are opened energized more often than any switchboard; a junction box with a splice is the one class the project adds where its maintenance practice opens boxes under load, and leaves out where it does not. The classes a project leaves out are the ones no worker opens energized. {note}
−### The 2-second cap is defensible for accessible above-ground equipment in a normal working position, but not for a worker in a pit, in a confined space, on a ladder, or in any other location from which escape in 2 seconds is unlikely. {note}
+### Every bus studied shall be identified in the model, the report, the label schedule, and the one-line diagram by the designation the contract documents give the equipment at that bus, as shown on [[drawing: the one-line diagram]].
−### The Engineer shall identify any location from which escape in 2 seconds is unlikely during the study and shall override the 2-second cap for those buses.
+### The study boundary shall extend downstream to the last item of each class selected, and the report shall state, for every class selected, the point below which no bus is calculated and the reason.
−## Working Distance {toc}
+### Where equipment below the study boundary carries an arc-flash label under its equipment standard, the label shall carry the incident energy calculated at the bus that feeds it, with the working distance of that bus, and the label schedule shall identify the bus the value is taken from.
−### Working distance is the distance from the arc source to the worker's face and chest. {note}
−### Incident energy at the working distance is what the label reports and what the PPE shall protect against.
−### IEEE 1584 provides typical working distances by equipment class. {note}
+## Line and Load Side of a Main Device {toc}
−| Equipment Class | Typical Working Distance |
−|-----------------|--------------------------|
−| Low-voltage MCC and panelboards | 18 in. (455 mm) |
−| Low-voltage switchgear and switchboards | 24 in. (610 mm) |
−| Medium-voltage switchgear | 36 in. (910 mm) |
−| Cable | 18 in. (455 mm) |
+### Where a section contains a main device, the study shall calculate the line side of the main, cleared by the next upstream device, and the load side of the main, cleared by the main, as two buses, and shall report each.
−### A task-specific working distance shorter than the typical value shall be used where the task being performed places the worker closer to the arc source than the typical value assumes.
+### Where the line-side and load-side results of a section differ, the label schedule shall state the line-side value for the section unless the equipment standard requires each compartment to carry its own value, in which case the schedule shall state both and identify the compartment each applies to.
−```datasheet
−label: Working Distance Basis
−type: radio
−options:
− - "IEEE 1584 typical values by equipment class"
− - "Task-specific working distance (justified per task)"
−default: "IEEE 1584 typical values by equipment class"
−```
+### The main breaker protects everything below it and nothing above it. An arcing fault on its line terminals, in the incoming compartment, or on the bus of a transformer secondary, is cleared by the device on the primary side of the transformer, which sees the arcing current reduced by the turns ratio and often sits on its long-time curve for seconds. That is why the main section of a switchboard is routinely the highest-energy bus in a building, and why a single label for the section states the line-side value. {note}
−### The label shall report the incident energy at the working distance assumed in the calculation, and that distance shall be stated on the label.
+# Cases {toc}
−## Modeling Boundary {toc}
+## Bolted Fault Current Cases {toc}
+### The study shall calculate every bus at the bolted fault current cases indicated in the datasheet, as delivered by the short-circuit study under [[sync/short-circuit-study]].
+
```datasheet
−label: Downstream Modeling Limit
−type: select
+label: Bolted Fault Current Cases
+type: radio
options:
− - "Every branch-circuit panelboard"
− - "Every MCC bucket and motor disconnect"
− - "Every distribution panelboard 100A and above"
− - "Every piece of equipment 240V and above"
− - "Project-specific (see scope statement)"
−default: "Every branch-circuit panelboard"
+ - "Maximum bolted fault current with the arcing current variation applied"
+ - "Maximum and minimum bolted fault current, each with the arcing current variation applied"
+default: "Maximum and minimum bolted fault current, each with the arcing current variation applied"
```
−### The model shall extend from the utility source down to the lowest level of distribution at which workers will perform energized tasks.
+### A lower fault current does not mean a lower incident energy. The arcing current falls with the bolted current, and when it falls below the instantaneous pickup of the upstream device the clearing time jumps from a few cycles to the time-delay band or the long-time curve, and the energy rises with it. The maximum case with the arcing current variation catches that effect over the variation the model expects at one bolted current; the minimum case, with the utility at its minimum contribution and the motors and the smallest source configuration, catches it where the utility's own range is wider than the variation, as on a service fed from a weak or switched utility system. A project runs the maximum case alone where the short-circuit study delivered no minimum. {note}
−### Equipment below the modeling boundary may be analyzed by inference from its upstream device, provided the inference is documented and the worker-facing label is conservative.
+## Arcing Current Variation {toc}
−### The Engineer shall set the downstream limit consistent with the work that will actually be performed energized.
+### At every bus the incident energy shall be calculated at the arcing current and at the reduced arcing current that the arcing current variation correction factor of IEEE 1584-2018 gives, each with the clearing time read at that current, and the higher of the two incident energies and the larger of the two arc-flash boundaries shall be reported for the bus.
−### Where a class of equipment will never be opened energized, that equipment shall instead be labeled with a generic warning and an instruction to de-energize before opening.
+### The results tables shall show both arcing currents, both clearing times, and both incident energies at every bus, and a results table that shows one arcing current per bus shall not be accepted.
−## Equipment Below 240V {toc}
+### The arcing current variation replaces the fixed 0.85 multiplier of the 2002 edition with a correction that depends on the voltage, the gap, the configuration, and the fault current, and it is the step most often found missing in a study converted from a 2002 model by changing the edition setting. A bus whose reduced arcing current sits below a pickup that the full arcing current clears is a bus with two labels' worth of difference between the two runs. {note}
−### The analyst shall model buses below 240V by the 2018 method, because the 2018 edition deprecated the 2002 edition's exemption for equipment below 240V served by transformers smaller than 125kVA and recognizes that arcs can sustain at 208V given sufficient available current.
+## Source Operating Cases {toc}
−### Where the calculated incident energy is low enough that the equipment does not need a hazard label, the equipment shall still be modeled in the report and the low-energy result documented.
+### The study shall calculate every bus in every operating case indicated in the datasheet that supplies it, and the highest incident energy at each bus across the cases the worker can meet shall be the value reported for the bus.
−### The report shall not assert that equipment below 240V is exempt.
−
−# Input Data Requirements {toc}
−
−## Upstream of the Service {toc}
−
```datasheet
−label: Utility Source Fault Current Data
−type: select
+label: Source Operating Cases
+type: checkbox
options:
− - "Utility-provided three-phase and single-line-to-ground available fault current at the service"
− - "Utility-provided infinite-bus equivalent (with documented system X/R)"
− - "Assumed value pending utility confirmation"
−default: "Utility-provided three-phase and single-line-to-ground available fault current at the service"
+ - "Utility source in normal configuration"
+ - "Each on-site generator or generator plant alone"
+ - "Utility and on-site generation paralleled"
+ - "Ties closed between services or transformers"
+ - "UPS, energy storage, and photovoltaic sources in bypass and in inverter operation"
+ - "Maintenance bypass of paralleling switchgear and transfer equipment"
+default:
+ - "Utility source in normal configuration"
+ - "Each on-site generator or generator plant alone"
+constraint: all_of
```
−### Utility fault current shall be obtained in writing from the serving utility.
+### A generator alone delivers less fault current than the utility and clears more slowly, because its decrement drops the arcing current into the time-delay bands of the devices below it, and the incident energy on generator power is routinely higher than on utility power at the same bus; the utility and the generation paralleled gives the sum of both at every bus between them and is the case for the paralleling bus and the main switchgear during a closed transition or in extended parallel operation; a tie closed between two services or two transformers doubles the source behind the common bus, and is a case whether or not the operating procedure forbids it, because the tie can be closed; a UPS or an inverter in bypass passes the upstream source through to loads that on inverter power see only the current limit; the maintenance bypass of paralleling switchgear or of a transfer switch puts a bus on a source and a clearing device it is never on in normal operation, and is the case the paralleling switchgear standard requires on the bypassed distribution's label. A case left out is a configuration in which a worker can open a door against a number no one has calculated. {note}
−### An assumed value is acceptable for a preliminary study only and shall be reconciled before the labels are produced.
+### Where a case produces the highest incident energy at a bus only during a transfer or a closed transition and no worker performs an energized task in that state, the study engineer shall document the state and its result in the report and shall exclude it from the label value, with the exclusion recorded in the assumption register.
−### The utility data shall include both the maximum available fault current and, where the utility can provide it, a minimum available fault current corresponding to a single-source contingency on the utility side, which drives the minimum-arcing-current case.
+### Where the equipment standard requires the label on an item of equipment to state more than one operating state, as the tie-open and tie-closed values on a double-ended substation or the bypass state on a paralleling switchgear, the study shall report each state separately and the label schedule shall carry each.
−## Equipment Data {toc}
+### Where a generator source is calculated, the arcing current shall be read against the generator's decrement, and the clearing time shall be read from the device curve at the current the generator sustains at the time of clearing rather than at its subtransient current.
−### The analyst shall collect, for every piece of modeled equipment, the data required by the IEEE 1584 model:
+## Maintenance-Mode Cases {toc}
−- Nominal voltage and configuration (3-phase 3-wire, 3-phase 4-wire)
−- Frame size and short-circuit current rating
−- Enclosure dimensions (height, width, depth) where the equipment is enclosed
−- Bus gap (electrode spacing) per the manufacturer's published data
−- Electrode configuration (per the table above)
−- Conductor size, type, and length from the upstream source
−- Transformer kVA, impedance, and connection where transformers are within the model
+### At every bus whose clearing device carries an energy-reducing maintenance switch, the study shall calculate the incident energy with the switch in its normal state and in its maintenance state, and shall carry the results to the label as indicated in the datasheet.
```datasheet
−label: Equipment Data Collection Method
+label: Maintenance Switch Values on the Label
type: radio
options:
− - "Field survey by the analyst"
− - "Owner-provided equipment list (verified by spot-check field survey)"
− - "Manufacturer shop drawings (new construction)"
−default: "Field survey by the analyst"
+ - "Normal-state and maintenance-state values both on the label"
+ - "Maintenance-state value on the label with the instruction to place the switch in maintenance before opening"
+ - "Normal-state value on the label and the maintenance-state value in the report"
+default: "Normal-state and maintenance-state values both on the label"
```
−### Enclosure dimensions and bus gap, new requirements introduced by the 2018 edition, shall be obtained from the equipment manufacturer's published data or, where the equipment is in service and not documented, from physical measurement of representative units.
+### Both values on the label let the worker see what the switch buys and choose the PPE for the state the switch is in, at the cost of a label with two numbers that a worker in a hurry can read wrong; the maintenance-state value alone with the instruction to engage the switch first is the arrangement where the Owner's program makes engaging the switch a step of every energized task at that equipment and the switch's status light is visible with the door closed, and it leaves the worker unprotected on the day the switch is bypassed or failed; the normal-state value alone on the label treats the switch as a bonus the label does not count on, gives the most conservative PPE, and loses the reduction the switch was bought for. {note}
−### For new construction, manufacturer shop drawings are the authoritative source. {note}
+### At every bus whose clearing device is in a zone-selective interlocking scheme, the study shall calculate the incident energy with the interlock active, and the report shall identify each such bus and shall state that the value depends on the interlock wiring being continuous and the scheme enabled.
−### For an existing facility, a field survey by the analyst is the safest approach because nameplate ratings and as-installed configurations frequently diverge from the original record drawings. {note}
+### At every bus whose clearing device is an energy-reducing active arc-flash mitigation system or an optical arc-flash relay, the study shall calculate the incident energy at the clearing time the manufacturer publishes for the system furnished, and shall also report the value with the system out of service.
−## Protective Device Settings {toc}
+### At a bus in arc-resistant switchgear tested to IEEE C37.20.7, the study shall calculate and label the incident energy with the compartment door open, and the report shall state that the arc-resistant rating applies only with every door closed and latched.
−```datasheet
−label: Protective Device Setting Verification
−type: radio
−options:
− - "Field-verified settings (every device in the model)"
− - "Coordination-study settings (assumed installed correctly)"
−default: "Field-verified settings (every device in the model)"
−```
+### The maintenance switch, the interlock, the active mitigation system, and the arc-resistant enclosure are furnished and tested under the equipment standards; this study calculates what each does to the energy at the bus and tells the worker which of them the label counts on. A label that quietly assumes an interlock that was never commissioned is the failure the per-bus statement of dependence exists to prevent. {note}
−### Protective device settings shall be the as-set values from the coordination study, confirmed by field verification.
+# Arc-Flash Input Data {toc}
−### The arc-flash analyst shall not assume settings or take settings from a design submittal that has not been confirmed in the field.
+## Data Inherited from the Short-Circuit Study {toc}
−### Where the field verification finds a device set differently than the coordination study assumed, the discrepancy shall be resolved — either by adjusting the device to the studied setting or by re-running the arc-flash calculation with the as-found setting — before labels are produced.
+### The bolted fault current, the X/R, the utility contribution, the transformer, conductor, busway, motor, generator, and inverter data, the source operating configurations, the existing-equipment survey, and the assumption register shall be taken from the accepted short-circuit study under [[sync/short-circuit-study]], and the arc-flash study shall not collect, re-enter, or revise them.
−# Maintenance Mode Analysis {toc}
+### Where the study engineer finds an input of the short-circuit model that the arc-flash results are sensitive to and believes to be wrong, the finding shall be reported to the Engineer of Record and to the short-circuit study engineer, and the model shall be revised under [[sync/short-circuit-study]] and both predecessor studies re-run before this study is issued on the revised model.
−## Energy Reduction Methods {toc}
+### An arc-flash study collects four inputs the system model does not already carry, the electrode configuration, the enclosure dimensions, the bus gap, and the working distance at each bus, and everything else it reads is already in the model it inherits. A study that re-collects the utility letter and re-enters the transformer impedances is building a second model, and the two will differ by the time the labels are printed. {note}
−### NFPA 70 Article 240.87 requires that any circuit breaker rated 1200A or more, or any breaker with a continuous current setting of 1200A or more, employ one of the following methods to reduce arcing duration:
+## Electrode Configuration {toc}
−- Zone-selective interlocking (ZSI)
−- Differential relaying
−- Energy-reducing maintenance switching (ERMS, also called arc-reduction maintenance switch or ARMS) with a local status indicator
−- Energy-reducing active arc-flash mitigation system
−- An instantaneous trip setting less than the available arcing current
−- An instantaneous override setting less than the available arcing current
−- An approved equivalent means
+### The electrode configuration at every bus shall be established on the basis indicated in the datasheet.
```datasheet
−label: Arc Energy Reduction Method Applied to 1200A+ Breakers
+label: Electrode Configuration Basis
type: select
options:
− - "Zone-selective interlocking (ZSI)"
− - "Differential relaying (87)"
− - "Energy-reducing maintenance switching (ERMS)"
− - "Energy-reducing active arc-flash mitigation system"
− - "Instantaneous trip setting below available arcing current"
− - "Approved equivalent"
−default: "Zone-selective interlocking (ZSI)"
+ - "Per bus, from the construction of the equipment furnished or installed"
+ - "VCB for enclosed equipment and VOA in open air throughout"
+ - "Most severe enclosed configuration for each voltage class throughout"
```
+### IEEE 1584-2018 tests five configurations, vertical conductors in a box (VCB), vertical conductors terminating in an insulating barrier in a box (VCBB), horizontal conductors in a box (HCB), and vertical and horizontal conductors in open air (VOA and HOA), and at the same bus the configuration alone moves the incident energy by a factor of two or more, with VCBB and HCB above VCB in a low-voltage enclosure. Setting the configuration per bus, from the compartment the worker actually opens, gives the value the equipment presents, at the cost of a survey of each equipment class and a judgment where a compartment holds more than one geometry; VCB for every enclosure and VOA in open air is the setting the software ships with and the one most studies run, and it understates the energy at a bus whose exposed conductors are horizontal or terminate on a barrier, as the line terminals of a panelboard main and the bus stabs of a motor control center; the most severe enclosed configuration for each voltage class overstates the energy at every bus with a vertical geometry, which is most of them, and buys a conservative label at the cost of PPE and of mitigation recommended where none is needed. {note}
+
+### The configuration applied at each bus shall be stated in the results tables and in the label schedule, and where a compartment presents more than one configuration to a worker, the configuration giving the higher incident energy shall govern that bus.
+
+## Enclosure Dimensions {toc}
+
+### The enclosure height, width, and depth at every enclosed bus shall be established on the basis indicated in the datasheet, and the enclosure size correction factor of IEEE 1584-2018 shall be applied from them.
+
```datasheet
−label: ERMS Reporting on Label
+label: Enclosure Dimension Basis
type: radio
options:
− - "Show both normal and maintenance-mode incident energy"
− - "Show maintenance-mode value only (ERMS required to interact)"
− - "Show normal-mode value only (ERMS not provided)"
−default: "Show both normal and maintenance-mode incident energy"
+ - "IEEE 1584-2018 typical enclosure dimensions by equipment class"
+ - "Dimensions of the equipment furnished or installed, per bus"
+default: "IEEE 1584-2018 typical enclosure dimensions by equipment class"
```
−### Where ERMS is employed, the device has two distinct states with different incident energy, and the analysis shall calculate and report the incident energy in both the normal-operation and maintenance-mode states.
+### The typical enclosure dimensions IEEE 1584-2018 tabulates for each equipment class are the values nearly every study applies, because the correction factor is modest over the range of real enclosures and a measured dimension changes the energy at a bus by less than the uncertainty in its clearing time; the dimensions of the equipment furnished, taken from the shop drawings or measured at an existing item, are the basis a project selects where a compartment is far smaller than its class, as a shallow motor disconnect or a small junction box, where the correction factor rises with the smaller volume and the typical value understates the energy. {note}
−### The label shall show the incident energy in both states or, where the equipment is wired to require ERMS engagement before doors can be opened, shall show only the maintenance-mode value with a notation that the equipment requires ERMS engagement prior to interaction.
+### Where the dimensions of the equipment furnished are selected, the dimensions shall be the inside dimensions of the compartment the worker opens, taken from the manufacturer's shop drawings for new equipment and from measurement for existing equipment, and recorded in the input data tables.
−### ZSI operates continuously and does not have a worker-engaged state in the same way ERMS does, but a ZSI scheme that has been disabled or whose interlock signal has been disconnected provides no benefit. {note}
+## Bus Gap {toc}
−### The analysis shall confirm that ZSI is in fact active in the as-installed wiring.
+### The gap between conductors at every bus shall be established on the basis indicated in the datasheet.
−### The arc-flash report shall identify ZSI buses and recommend periodic functional verification of the interlock.
+```datasheet
+label: Bus Gap Basis
+type: radio
+options:
+ - "IEEE 1584-2018 typical gaps by equipment class and voltage"
+ - "Gap of the equipment furnished or installed, per bus"
+default: "IEEE 1584-2018 typical gaps by equipment class and voltage"
+```
−## Other Operating States {toc}
+### The typical gaps IEEE 1584-2018 tabulates by equipment class and voltage, 25 mm for a low-voltage panelboard and motor control center, 32 mm for low-voltage switchgear, 104 mm for 5 kV switchgear and 152 mm for 15 kV switchgear, are the values nearly every study applies, because the gap enters the arcing current and the energy weakly over the range any one class spans; the gap of the equipment furnished, from the manufacturer's data or a measurement, is the basis a project selects at medium voltage, where the range across designs is wide and a 15 kV compartment built to a 104 mm gap is calculated at a 152 mm gap otherwise. {note}
−### The analysis shall consider operating states that affect available fault current and clearing time:
+### Where the gap of the equipment furnished is selected, the gap shall be the shortest phase-to-phase clearance between exposed conductors in the compartment the worker opens, taken from the manufacturer's data for new equipment and from measurement for existing equipment, and recorded in the input data tables.
−- Alternate-source operation (generator running, normal source unavailable)
−- Tie-breaker closed on multi-source systems
−- Bypass operation of a UPS or static switch
−- Maintenance bypass of a paralleling switchgear
+## Working Distance {toc}
+### The working distance at every bus in a low-voltage panelboard, motor control center, controller, disconnect switch, busway plug-in unit, transfer switch, control panel, or junction box shall be the distance indicated in the datasheet.
+
```datasheet
−label: Alternate Operating States Analyzed
−type: checkbox
+label: Working Distance for Panelboards, Motor Control Centers, and Small Enclosures
+type: range
+unit: in
options:
− - "Normal utility source"
− - "Standby generator (utility unavailable)"
− - "Multi-source with tie closed"
− - "UPS bypass"
− - "Maintenance bypass / paralleling switchgear"
−default: "Normal utility source"
+ min: 12
+ max: 48
+ setpoints: [12, 18, 24, 36, 48]
+default: 18
+constraint: exact
```
−### The reported incident energy at each bus shall be the worst-case value across all credible operating states.
+### The working distance at every bus in low-voltage switchgear and in a switchboard shall be the distance indicated in the datasheet.
−### Where a state produces a higher incident energy only briefly during a transfer, the analyst shall document the state and may exclude it if it is not a state in which workers will perform energized tasks.
−
−# Equipment Labeling Requirements {toc}
−
−## Required Label Content {toc}
−
```datasheet
−label: Label Method
−type: radio
+label: Working Distance for Low-Voltage Switchgear and Switchboards
+type: range
+unit: in
options:
− - "Incident energy analysis method (engineered values)"
− - "PPE category method (NFPA 70E task tables)"
−default: "Incident energy analysis method (engineered values)"
+ min: 12
+ max: 48
+ setpoints: [12, 18, 24, 36, 48]
+default: 24
+constraint: exact
```
+### The working distance at every bus in medium-voltage switchgear and in a medium-voltage transformer or controller compartment shall be the distance indicated in the datasheet.
+
```datasheet
−label: Minimum Label Content
−type: checkbox
+label: Working Distance for Medium-Voltage Equipment
+type: range
+unit: in
options:
− - "Nominal system voltage"
− - "Arc-flash boundary (distance)"
− - "Available incident energy (cal/cm²)"
− - "Working distance for the reported incident energy"
− - "Minimum arc rating of required PPE (cal/cm²)"
− - "Site-specific PPE description"
− - "Equipment identifier matching the single-line diagram"
− - "Date of the study"
− - "Engineer's seal or study report reference"
−default: "Nominal system voltage"
+ min: 12
+ max: 48
+ setpoints: [12, 18, 24, 36, 48]
+default: 36
+constraint: exact
```
−### Per NFPA 70E 130.5(H), each piece of equipment within the scope of the study shall be field-marked with a label containing, at a minimum, the nominal system voltage, the arc-flash boundary, and at least one of the following: available incident energy and corresponding working distance, minimum arc rating of clothing, site-specific level of PPE, or hazard/risk category from the NFPA 70E task tables.
+### The working distance is the distance from the arc to the worker's face and chest, and the incident energy falls with roughly the square of it, so the distance decides the label as much as the clearing time does. The three defaults, 18 in for a panelboard or a motor control center, 24 in for low-voltage switchgear and switchboards, and 36 in for medium-voltage switchgear, are the typical distances IEEE 1584-2018 tabulates and the ones the label is read at; a project shortens the distance at an equipment class where its tasks put the worker's face closer, as a panelboard mounted so that the worker crouches at it, and lengthens it only where every energized task at the class is performed with a tool that keeps the worker further away. {note}
−### This standard requires the incident-energy method for all labels, because a site that has performed the engineering study should report its actual results rather than the PPE-category tabular shortcut. {note}
+### Where a task at a bus is performed closer than the working distance of its equipment class, the study shall also report the incident energy at the task distance, and the label schedule shall carry the value at the equipment class distance with the task value in the report.
−### The label shall use one selection method consistently, because the 2024 edition of NFPA 70E explicitly prohibits showing both an incident-energy value and a PPE category from the task tables on the same label.
+### The working distance applied at each bus shall be stated in the results tables and shall be the distance printed on the label with the incident energy.
−## Label Format and Hazard Word {toc}
+# Clearing Time {toc}
−### The hazard signal word on the label shall be selected per ANSI Z535.4 and NFPA 70E based on the incident energy:
+## Clearing Device and Settings {toc}
−| Incident Energy | Signal Word |
−|-----------------|-------------|
−| Up to 1.2 cal/cm² | CAUTION (no PPE required for typical tasks; verify the no-hazard task assumption) |
−| 1.2 to 40 cal/cm² | WARNING |
−| Greater than 40 cal/cm² | DANGER — no safe PPE available; equipment shall not be worked energized |
+### The arc duration at every bus shall be the clearing time of the device that clears an arcing fault at that bus, read from its time-current curve at the arcing current and at the reduced arcing current, at the settings accepted under [[sync/protective-coordination-study]].
−```datasheet
−label: Label Signal Word Application
−type: radio
−options:
− - "Per ANSI Z535.4 / incident-energy thresholds above"
− - "Uniform WARNING on all labels (legacy practice)"
−default: "Per ANSI Z535.4 / incident-energy thresholds above"
−```
+### The clearing device for a bus shall be the first device upstream of the exposed conductors the worker reaches, and a device in the same compartment as those conductors shall not be taken as clearing a fault on its own line side.
−### Buses with incident energy above 40 cal/cm² shall be labeled DANGER with a notation that no commercially available PPE provides reliable protection at that energy level.
+### Where the clearing device is a circuit breaker whose published trip curve ends at the trip unit's signal to the breaker, the breaker's opening time, as the manufacturer publishes it and as IEEE C37.13 or UL 489 rates it, shall be added to the time read from the curve.
−### The Owner shall identify the buses with incident energy above 40 cal/cm² in the electrical safety program and shall require de-energization before any work is performed.
+### Where the clearing device is a current-limiting fuse or a current-limiting breaker operating in its current-limiting range at the arcing current, the clearing time and the incident energy shall be taken from the fuse or breaker manufacturer's published arc-flash data or from the total clearing curve, and the current-limiting let-through shall not be credited without that data.
−## Label Construction {toc}
+### Where the clearing device is a relay-operated breaker, the arc duration shall be the relay operating time at the arcing current plus the breaker interrupting time of IEEE C37.010 for its rated interrupting time, plus the time of any lockout or auxiliary relay in the trip path.
−```datasheet
−label: Label Material
−type: select
−options:
− - "Polyester with adhesive backing (indoor, conditioned space)"
− - "Vinyl with UV-resistant overlaminate (indoor industrial / unconditioned)"
− - "Engraved phenolic plate, mechanically fastened (outdoor / harsh environment)"
− - "Stainless steel with engraved or etched lettering (outdoor / corrosive)"
−default: "Polyester with adhesive backing (indoor, conditioned space)"
−```
+### Where the clearing device is a transformer primary device clearing a fault on the secondary, the arcing current shall be reflected through the transformer ratio and connection before the curve is read.
+### Every setting the study reads shall be listed in the input data tables with the device, the setting, and the revision of the coordination study it was taken from, and a setting taken from any other source shall be identified as such and shall not be printed to a label.
+
+### The curve says when the trip unit decides; the arc ends when the contacts part and the arc inside the breaker goes out. For a low-voltage power breaker the difference is about three cycles, for a molded-case breaker about one, for a medium-voltage breaker three to five, and at a bus cleared on an instantaneous element it is most of the duration. A study that reads the curve and stops has every instantaneous bus wrong by a factor. {note}
+
+## Arc Duration Cap {toc}
+
+### Where the clearing device does not clear within two seconds at the arcing current, the arc duration shall be treated as indicated in the datasheet.
+
```datasheet
−label: Label Mounting Method
+label: Arc Duration Cap
type: radio
options:
− - "Adhesive on cleaned, dry equipment surface"
− - "Mechanical fasteners (screws or rivets)"
− - "Magnetic mount (movable equipment only)"
−default: "Adhesive on cleaned, dry equipment surface"
+ - "Two seconds where the worker can move away from the arc"
+ - "Device clearing time without a cap"
+default: "Two seconds where the worker can move away from the arc"
```
−### A label in a humid mechanical room, an outdoor switchyard, a chemical-process area, or a high-temperature switchgear room shall be of sufficient durability for that environment per the 2024 edition of NFPA 70E, and shall not fade, peel, or become unreadable within the periodic review interval.
+### IEEE 1584-2018 and NFPA 70E Informative Annex D note that a worker exposed to an arc is likely to have moved out of its reach within about two seconds, and nearly every study caps the duration there at a bus cleared on a long-time curve, because the uncapped value, often hundreds of calories, is an energy no PPE addresses and the cap is what makes the label a number a worker can act on; calculating the full clearing time leaves the label with that energy, which is the honest statement at a bus from which the worker cannot step away. {note}
−### Adhesive-backed labels in unconditioned spaces commonly fail within five years from heat cycling and ultraviolet exposure. {note}
+### Where the cap is selected, it shall not be applied at a bus a worker reaches from a ladder, a lift, a pit, a crawl space, a confined space, or a position in which an enclosure or an obstruction prevents stepping back, and the study engineer shall identify each such bus from the equipment locations and calculate it at the full clearing time.
−### For outdoor switchyards, generator yards, and rooftop equipment, an engraved phenolic plate or stainless-steel label mechanically fastened to the equipment shall be specified.
+### Every bus at which the cap is applied shall be identified in the results tables and in the report, with the uncapped clearing time shown beside the capped one.
−## Label Location {toc}
+# Label Content and PPE {toc}
+## Label Method {toc}
+
+### The arc-flash label at every bus within the study boundary shall state the hazard by the method indicated in the datasheet, and shall not state it by both.
+
```datasheet
−label: Label Granularity
−type: select
+label: Label Method
+type: radio
options:
− - "Per equipment lineup only"
− - "Per section (vertical section of switchgear, column of MCC)"
− - "Per individual device (each breaker, each bucket)"
−default: "Per section (vertical section of switchgear, column of MCC)"
+ - "Incident energy analysis method"
+ - "Arc flash PPE category method of NFPA 70E Table 130.7(C)(15)"
+default: "Incident energy analysis method"
```
−### Labels shall be installed on each piece of equipment in a location where they are visible to a worker before that worker opens, racks, or otherwise interacts with the equipment energized.
+### NFPA 70E 130.5(F) permits either the incident energy analysis method or the PPE category method on a given item of equipment and forbids both on the same one. The incident energy method prints the calculated energy at the working distance and is the method on every project that has performed this study, because the study exists to produce the number; the PPE category method prints a category from the tables of NFPA 70E 130.7(C)(15), which apply only to the equipment types, fault currents, and clearing times the tables list, and is selected where the Owner's program is built on categories and every bus falls within the table parameters. A label that prints a category beside a calculated energy invites the worker to pick whichever reads lower. {note}
−### For lineup equipment such as switchgear and motor control centers, a label shall be applied to each section, each individually drawable breaker, and each MCC bucket — not only to the equipment as a whole.
+### Where the PPE category method is selected, the study shall confirm at every bus that the equipment type, the available fault current, and the clearing time lie within the parameters of NFPA 70E Table 130.7(C)(15), and shall label by the incident energy analysis method at every bus that does not.
−### Per-section labeling is the practical compromise for most installations and is the basis for the cost and label-count estimates in the study. {note}
+### The label method selected here shall be the method the Owner's electrical safety program under [[sync/electrical-safety-program]] selects, and where the two differ the Engineer of Record shall resolve the difference before the label schedule is issued.
−### Per-device labeling shall be specified at the start of the project where it is required by the Owner's safety program, because retrofitting per-device labels after a per-section study approximately doubles the label count.
+## Label Content {toc}
−### The label location on each piece of equipment shall be repeatable and shall not be obscured by handles, hinges, latches, or routine maintenance hardware.
+### Each arc-flash label shall carry the content indicated in the datasheet, with every value taken from the label schedule for that bus.
−### Where the equipment door swings outward, the label shall be on the door at the worker's eye level; where the worker approaches the equipment from the side, the label shall be on the side panel.
+```datasheet
+label: Label Content
+type: checkbox
+options:
+ - "Nominal system voltage"
+ - "Arc-flash boundary"
+ - "Incident energy at the working distance"
+ - "Working distance"
+ - "Minimum arc rating of PPE"
+ - "Site-specific PPE level"
+ - "Arc flash PPE category"
+ - "Limited approach boundary"
+ - "Restricted approach boundary"
+ - "Equipment designation matching the one-line diagram"
+ - "Protective device that clears the arc"
+ - "Date of the study"
+ - "Study report reference"
+default:
+ - "Nominal system voltage"
+ - "Arc-flash boundary"
+ - "Incident energy at the working distance"
+ - "Working distance"
+ - "Limited approach boundary"
+ - "Restricted approach boundary"
+ - "Equipment designation matching the one-line diagram"
+ - "Date of the study"
+constraint: all_of
+```
−### Label placement details shall be provided on representative equipment types — switchgear section, MCC column, panelboard cover, transformer enclosure. [[drawing: Label placement details on representative equipment types — switchgear section, MCC column, panelboard cover, transformer enclosure]]
+### Whatever the datasheet selects, each label shall carry at least the nominal system voltage, the arc-flash boundary, and one of the incident energy with its working distance, the minimum arc rating of PPE, the site-specific PPE level, or the PPE category, as NFPA 70E 130.5(H) requires, and a label on service or feeder equipment rated 1200 A and more shall also carry the date it reflects, as NFPA 70 110.16(B) requires.
−# Deliverables {toc}
+### Where the incident energy analysis method is selected, the label shall not carry a PPE category, and where the PPE category method is selected, the label shall not carry an incident energy value.
−## The deliverable set for the arc-flash study comprises three artifacts that shall be consistent with each other in every value.
+### The voltage, the arc-flash boundary, and the energy or the category are the three things NFPA 70E requires on the door, and the rest is what makes the label usable without the report: the working distance tells the worker what the energy was calculated at, the shock boundaries from NFPA 70E Table 130.4 put the approach limits where the arc-flash boundary is, the designation ties the door to the one-line and the schedule, the clearing device tells the next engineer what the value depends on, and the date tells the reviewer whether the label is current. A study report reference is added where the Owner's program requires the worker to be able to find the calculation; a site-specific PPE level is added where the Owner's program names its levels. {note}
−## Calculation Report {toc}
+### The limited and restricted approach boundaries printed on a label shall be those of NFPA 70E Table 130.4 for the nominal voltage of the bus, and the arc-flash boundary shall be the distance at which the incident energy is 1.2 cal/cm², calculated at the clearing time and arcing current that govern the bus.
−### The report shall include, at minimum:
+### Each label shall carry the signal word established under Signal Word and the values of the operating state or states the label is required to state under Source Operating Cases and Maintenance-Mode Cases.
−- Executive summary identifying the highest-incident-energy buses and the buses where incident energy exceeds 40 cal/cm²
−- System description with single-line diagram, bus identifiers, and the modeling boundary
−- Utility data source and date
−- Equipment data sources (field survey, manufacturer data, shop drawings)
−- Protective device settings table with the source of each setting (coordination study, field-verified, etc.)
−- Methodology statement identifying the IEEE 1584 edition, electrode configurations applied, working distances used, and any departures from the standard methodology
−- Bus-by-bus results table with bolted-fault current, arcing current (both max and min cases), arc duration, working distance, incident energy at the working distance, arc-flash boundary, label signal word, and required PPE
−- Mitigation recommendations for any bus where reasonable design changes could lower the incident energy meaningfully
−- Statement of assumptions and the conditions under which the study shall be reviewed or re-run
−- Engineer's seal and signature
+### The physical label, its material, its lettering, its pictogram, its attachment, and its location on each item of equipment are governed by [[sync/equipment-labeling]], and the label shall be ordered and installed under that standard from the label schedule of this study and from no other source.
−## Labels {toc}
+## Signal Word {toc}
−### The physical labels shall match the report values exactly.
+### The signal word on each label shall be assigned on the basis indicated in the datasheet, and the label schedule shall state it for every bus.
−### A discrepancy between the report and a label is a finding against the study and shall be corrected before closeout.
+```datasheet
+label: Signal Word Basis
+type: select
+options:
+ - "WARNING below 40 cal/cm² and DANGER at 40 cal/cm² and above"
+ - "WARNING below the arc rating of the highest PPE in the Owner's program and DANGER at and above it"
+ - "WARNING on every label"
+default: "WARNING below 40 cal/cm² and DANGER at 40 cal/cm² and above"
+```
−## Single-Line Diagram {toc}
+### ANSI Z535.4 reserves DANGER for a hazard that will cause death or serious injury if not avoided and WARNING for one that could, and NFPA 70E leaves the threshold between them to the facility. Forty calories per square centimeter was for many editions the line above which NFPA 70E assigned no PPE category, and it remains the threshold most programs use for DANGER and for the rule that the bus is not worked energized, which is why it is the basis on nearly every study; setting the threshold at the arc rating of the highest PPE the Owner stocks puts DANGER exactly where the Owner's workers have no protection, which on a program stocked to 40 cal/cm² is the same line and on one stocked to 65 or 100 cal/cm² is a higher one; WARNING on every label reads the signal word as a hazard class rather than a severity and leaves the worker to read the energy, which is the practice of a program that treats every energized task alike. {note}
−### The single-line diagram delivered with the study shall identify every modeled bus by the same identifier used on the labels and in the report.
+### Every bus whose incident energy at the working distance reaches 40 cal/cm² shall be listed separately in the report's executive summary, whatever signal word the datasheet assigns it, so that the Owner's program can identify the buses it will not work energized.
−### The single-line diagram shall be maintained as a controlled document for the life of the facility and shall be updated whenever the study is updated.
+## PPE Arc Rating {toc}
−# Worker Training Coordination {toc}
+### The report shall tabulate, for every bus, the arc rating of PPE the incident energy at the working distance requires, stated as indicated in the datasheet, for the Owner's electrical safety program under [[sync/electrical-safety-program]] to select PPE from.
```datasheet
−label: Owner Training Coordination
+label: PPE Statement in the Report
type: checkbox
options:
− - "Worker training on label interpretation"
− - "Energized-work permitting procedure references study"
− - "PPE inventory matched to study results"
− - "Periodic-review schedule established"
−default: "Worker training on label interpretation"
+ - "Minimum arc rating of PPE in cal/cm²"
+ - "Owner's site-specific PPE level"
+default:
+ - "Minimum arc rating of PPE in cal/cm²"
+constraint: all_of
```
−## The arc-flash study is an input to the Owner's electrical safety program, not a substitute for it. {note}
+### Where the Owner's site-specific PPE level is selected, the Owner shall furnish the arc rating of each level in the program before the final issue, and the study shall assign each bus the lowest level whose arc rating is not less than the incident energy at the working distance.
−## NFPA 70E requires that workers who perform tasks on or near energized equipment be trained as qualified persons, that they be familiar with the labels installed on equipment they will interact with, and that they be retrained at intervals not exceeding three years.
+### The minimum arc rating of PPE at a bus shall be not less than the incident energy at the working distance, as an arc rating under ASTM F1506 in cal/cm², and the table shall state the incident energy and the arc rating side by side.
−## The Contractor's responsibility under this standard ends at the delivery of the labels and the report.
+### The study produces the energy and the arc rating that meets it; the Owner's program decides which garments, which face protection, and which tasks go with each rating, and that division is why the table states the rating as a number and not as a garment. A site level is a convenience for a program that stocks three or four kits, and it is only as good as the arc rating the Owner attaches to it, which is why the Owner furnishes the ratings before the study assigns the levels. {note}
−## The Owner is responsible for incorporating the study results into worker training, energized-work permitting, PPE selection, and the periodic-review schedule.
+# Mitigation {toc}
−## The study shall identify, in its mitigation recommendations, any task-specific PPE that requires specification of a particular arc-rating beyond commodity electrical PPE.
+## Mitigation Threshold {toc}
−## The Owner shall procure any task-specific PPE identified by the study before workers are permitted to perform the affected tasks.
+### The report shall recommend mitigation at every bus whose incident energy at the working distance reaches the threshold indicated in the datasheet.
−# Re-Study Triggers {toc}
−
−## NFPA 70E 130.5(G) requires that the arc-flash risk assessment be reviewed periodically at intervals not exceeding five years, and reviewed whenever changes occur that could affect the analysis.
−
```datasheet
−label: Conditions Triggering Re-Study Before the Five-Year Interval
−type: checkbox
+label: Mitigation Recommendation Threshold
+type: range
+unit: cal/cm²
options:
− - "Utility available fault current change (notified by utility)"
− - "Service or main equipment replacement or upgrade"
− - "Protective device settings change (any device in the model)"
− - "Protective device replacement (new make or model)"
− - "Addition of significant new load (motors, transformers, generation)"
− - "Addition or removal of on-site generation"
− - "Configuration change (tie operation, bypass routing)"
− - "Discovery of a field condition inconsistent with the modeled assumptions"
−default: "Utility available fault current change (notified by utility)"
+ min: 1.2
+ max: 40
+ setpoints: [1.2, 4, 8, 12, 25, 40]
+constraint: exact
```
+### A threshold of 40 cal/cm² confines the recommendations to the buses the Owner's program will not work energized and is the arrangement where the aim is to make every bus workable; 25 cal/cm² adds the buses that require the heaviest PPE a program commonly stocks; 8 or 12 cal/cm² adds the buses above the daily-wear arc rating of most programs and is the threshold of an Owner whose aim is to perform routine tasks in daily wear; 1.2 or 4 cal/cm² asks for a recommendation at nearly every bus and is the arrangement of a study procured specifically to design a mitigation program. The threshold moves the length of the recommendation list and not the results. {note}
+
+## Mitigation Options Evaluated {toc}
+
+### For every bus at or above the threshold, the report shall evaluate each mitigation option indicated in the datasheet that applies to the bus, and shall state for each the incident energy that would result, the cost class of the change, and the operating consequence.
+
```datasheet
−label: Periodic Review Interval
−type: select
+label: Mitigation Options Evaluated
+type: checkbox
options:
− - "5 years (NFPA 70E maximum)"
− - "3 years (conservative)"
− - "Annual (high-change facilities)"
−default: "5 years (NFPA 70E maximum)"
+ - "Revised settings of the clearing device within the coordination constraints"
+ - "Energy-reducing maintenance switch on the clearing device"
+ - "Zone-selective interlocking between the clearing device and the devices below it"
+ - "Bus or transformer differential protection"
+ - "Current-limiting fuses or a current-limiting breaker ahead of the bus"
+ - "Optical arc-flash relay or active arc-flash mitigation system"
+ - "Arc-resistant switchgear construction"
+ - "Remote racking and remote operation outside the arc-flash boundary"
+ - "Relocation of the bus below a faster clearing device or a transformer"
+default:
+ - "Revised settings of the clearing device within the coordination constraints"
+ - "Energy-reducing maintenance switch on the clearing device"
+ - "Zone-selective interlocking between the clearing device and the devices below it"
+ - "Current-limiting fuses or a current-limiting breaker ahead of the bus"
+ - "Remote racking and remote operation outside the arc-flash boundary"
+constraint: all_of
```
−## The Owner shall maintain a record of the study date on every label and shall track the next review date in the facility records.
+### Every option on the list shortens the arc, moves the worker, or contains the blast, and each has a place. A revised setting costs nothing and is bounded by the selectivity the coordination study established; a maintenance switch cuts the energy only while a worker remembers to turn it on; zone-selective interlocking cuts it at every bus below the interlocked device at all times and needs wiring between the devices; differential protection clears a bus fault in a few cycles regardless of the arcing current and costs current transformers and a relay; a current-limiting fuse ahead of the bus ends the arc in a quarter cycle where the arcing current is in its current-limiting range and does nothing where it is not; an optical relay trips on the light of the arc in milliseconds; arc-resistant construction contains the arc with the doors closed and changes nothing with a door open; remote racking and operation move the worker outside the boundary for the tasks that start most arcs; relocating a bus below a faster device or a transformer is the design change that fixes the problem at the one-line. The options a project leaves off the list are the ones its equipment and its budget rule out before the study begins. {note}
−## A review at the five-year interval is not necessarily a full recalculation; the reviewer shall confirm that none of the re-study trigger conditions has changed since the prior study.
+### Where a revised setting is recommended, the recommendation shall be referred to the coordination study under [[sync/protective-coordination-study]] and shall not be printed to a label until that study has accepted the setting and this study has been re-run on it.
−## Where any re-study trigger condition has changed, the affected portion of the study shall be re-run and new labels produced for the affected buses.
+### The report shall present mitigation as recommendations ranked by the reduction each achieves, and the Owner and the Engineer of Record shall decide which to adopt; the study engineer shall not change the model, the settings, or the equipment to reflect a recommendation that has not been adopted in writing.
−## As part of the five-year review, the Owner shall request updated available fault current data from the serving utility and compare it to the value used in the study.
+### Where a recommendation is adopted, the equipment or setting change shall be made under the equipment standard or the coordination study that governs it, and the affected buses shall be re-run and re-issued under Study Revisions before the labels at those buses are printed.
−## Any material increase in utility available fault current requires re-running the study.
+### The hierarchy of controls in NFPA 70E puts elimination of the energized task first and PPE last, and the mitigation list is the middle of that hierarchy: the engineering controls that lower the energy a worker meets when the task cannot be eliminated. A study that reports the energy and stops has told the Owner where the problem is; one that prices the options has told the Owner what to do about it, and that is what the recommendation list is for. {note}
−## Utility fault current change is the trigger most commonly missed, because utilities increase available fault current as they reinforce their distribution system and the increase is not always communicated to the customer. {note}
+# Study Report {toc}
−## The Owner's maintenance procedures shall include notification of the responsible engineer when a protective device in the arc-flash model is replaced.
+## Report Content {toc}
−## A protective device replacement is the second commonly missed trigger, because a breaker replaced with one of different manufacture or trip-unit family may have substantially different clearing characteristics. {note}
+### The study report shall contain the following, in a single sealed document with numbered pages:
−## A 5-year interval is the NFPA 70E maximum and is appropriate for stable facilities with documented change-management procedures, while a shorter interval is appropriate where the facility undergoes frequent reconfiguration or change-management procedures do not reliably capture electrical-system modifications. {note}
+- a cover page with the project, the system studied, the study engineer, the issue and its date, the revision history, and the seal and signature required under Study Engineer
+- an executive summary stating the study boundary, the method, the cases, the highest incident energy in the system and where it occurs, every bus at or above 40 cal/cm², and every bus outside the IEEE 1584-2018 range
+- a system description and the one-line diagram described under One-Line Diagram
+- the method statement, giving the IEEE 1584-2018 edition, the method applied outside its range, the DC method, the software and its version and library revision, the independent verification required under Calculation Tool, the arc duration cap and where it was applied, and the label method
+- the statement of the short-circuit study revision and the coordination study revision the study was built on
+- the input data tables for the electrode configuration, enclosure dimensions, bus gap, and working distance at every bus, each with its basis and source, and for every clearing device with its settings and their source
+- the assumption register, carried forward from the short-circuit study and extended with every assumption of this study
+- the results tables, giving at every bus, for every case, the bolted fault current, the arcing current and the reduced arcing current, the clearing device and the clearing time at each, the incident energy at each, the governing incident energy, the arc-flash boundary, the working distance, the signal word, and the PPE arc rating
+- the maintenance-mode results at every bus that has them, described under Maintenance-Mode Cases
+- the mitigation recommendations described under Mitigation
+- the label schedule described under Label Schedule
+- the PPE arc rating table described under PPE Arc Rating
+- the re-study trigger list described under Review and Re-Study Triggers
+- appendices holding the manufacturer data for the fuses, breakers, and mitigation systems whose published arc-flash data the study relied on
−# Mitigation Hierarchy {toc}
+### The results tables shall be organized by bus in the order of the one-line diagram, so that the reader can follow the incident energy from the service to any bus without searching the report.
−## The study report shall identify mitigation options for buses with incident energy that would require Category 3 (25 cal/cm²) or higher PPE, or that exceed 40 cal/cm².
−## Mitigation shall be evaluated in the following order, which corresponds to the hierarchy of controls in NFPA 70E and reflects effectiveness from most to least:
+## One-Line Diagram {toc}
−1. Eliminate the need to work on the equipment energized (de-energize, lock out, verify)
−2. Substitute the equipment for a design with lower arcing characteristics (arc-resistant switchgear, current-limiting fuses upstream)
−3. Engineer the protective system for faster clearing (faster instantaneous, ZSI, ERMS, differential)
−4. Administrative controls (restrict tasks, increase working distance, require remote operation)
−5. PPE (last line of defense)
+### The report shall include a one-line diagram of the studied system showing every source, bus, protective device, and clearing relationship, with the designation of each bus as the contract documents give it, and at every bus the governing incident energy, the arc-flash boundary, and the working distance.
−```datasheet
−label: Mitigation Recommendations Provided In Report
−type: radio
−options:
− - "For every bus exceeding 8 cal/cm²"
− - "For every bus exceeding 25 cal/cm²"
− - "For every bus exceeding 40 cal/cm² only"
−default: "For every bus exceeding 25 cal/cm²"
−```
+### The one-line diagram shall carry the same bus identifiers as the short-circuit study, the coordination study, the results tables, the label schedule, and the labels, and no bus shall carry two identifiers across the three studies.
−## The report shall present mitigation as engineering recommendations, not as design changes.
+### Where the system is too large for one sheet, the diagram shall be divided across sheets with cross-references at every cut, and no bus shall appear on two sheets with two different values.
−## The Owner and Engineer of Record shall decide which recommendations to implement; the analyst's role is to identify the options and the order-of-magnitude reduction each would achieve.
+## Label Schedule {toc}
−## Where a mitigation recommendation is adopted, the affected portion of the study shall be re-run with the changed conditions and new labels produced.
+### The report shall include a label schedule listing, for every item of equipment that is to carry an arc-flash label, the bus identifier, the equipment designation, the location, the compartment or section the label applies to, the operating state or states the label states, and every value the label is to carry under Label Content, with the signal word.
−# Field Verification {toc}
+### The label schedule shall be delivered in an editable tabular form in addition to the sealed report, so that the labels can be produced from it under [[sync/equipment-labeling]] without transcription.
−## Before the labels are released for installation, the Contractor shall verify that the field conditions match the study assumptions.
−## The verification shall include, at minimum:
+### The label schedule shall match the results tables in every value, and a label that disagrees with the schedule or a schedule that disagrees with the results tables is a defect of the study to be corrected before the label is installed.
−- Protective device settings read at each device in the model and compared to the report's setting table
−- Available fault current at the service compared to the utility data used in the study
−- Equipment identifiers on the equipment match the identifiers used in the report
−- Any ERMS or similar maintenance-mode switches are functional and wired as the report assumes
−- Any ZSI interlock signals are continuous through every device in the scheme
+### The schedule is the handoff. The report is read by the engineer who reviews it; the schedule is read by the printer who makes the labels and by the electrician who installs them, and it has to carry everything they need in one row per door, so that no one is reading a value off a results table at the print shop. {note}
+## Report Format {toc}
+
+### The report shall be delivered in the formats indicated in the datasheet.
+
```datasheet
−label: Pre-Installation Verification
+label: Report Format
type: checkbox
options:
− - "Protective device settings verified at every device"
− - "Utility fault current re-confirmed at study delivery"
− - "Equipment identifier reconciliation"
− - "ERMS functional verification"
− - "ZSI continuity verification"
−default: "Protective device settings verified at every device"
+ - "Sealed report in searchable PDF"
+ - "Native model files of the analysis software"
+ - "Label schedule in editable tabular form"
+ - "Editable one-line diagram in CAD format"
+ - "Bound printed copies"
+default:
+ - "Sealed report in searchable PDF"
+ - "Native model files of the analysis software"
+ - "Label schedule in editable tabular form"
+constraint: all_of
```
−## Any discrepancy found during verification shall be resolved before labels are installed.
+### The sealed PDF is the record, the native model is what the five-year review opens, the editable schedule is what the labels are printed from, the editable one-line is what the Owner's drafting staff fold into the record drawings, and the printed copy is what sits in the electrical room with the safety program; a project adds the last two where its record-drawing and closeout practice call for them. {note}
−## Installing a label that does not match the as-installed condition is worse than no label at all, because it creates a false sense of protection. {note}
+### Where the native model files are selected, they shall be delivered under the condition stated under Closeout Submittals, and the report shall name the software version that opens them.
−# Delivery, Storage, and Handling {toc}
+# Study Revisions and Review {toc}
−## The calculation report, the native software project file, and the photographic record of installed labels shall be delivered to the Owner in both printed and electronic form.
+## Study Revisions Within the Project {toc}
−## The electronic form shall be on durable media or in a managed document repository that the Owner controls.
+### The study engineer shall correct every calculation error and reporting error in the study that is identified before the end of the project's correction period, and shall re-issue the affected pages, the label schedule rows, and the native model, at no cost to the Owner.
−## Reliance on a contractor's cloud storage account for the only copy of the study is not acceptable; the Owner shall be able to retrieve and edit the study without contacting the original analyst.
+### The study shall be revised whenever, after the final issue and before the equipment within the study boundary is energized, the short-circuit model is revised under [[sync/short-circuit-study]], a setting is changed under [[sync/protective-coordination-study]], the as-left settings record differs from the settings used, a mitigation recommendation is adopted, or the equipment furnished at a bus differs in its configuration, enclosure, or gap from the equipment modeled, and the revision shall re-run every bus the change affects.
−## Spare labels — at least one duplicate of each installed label — shall be delivered to the Owner for replacement of labels damaged in service.
+### A revision caused by a substitution or a change in the equipment furnished or the settings applied by the Contractor shall be made at the Contractor's cost, and a revision caused by a change in the utility's value, an existing condition, or the design shall be made as the Engineer of Record directs under the change provisions of the contract.
−## Spare labels shall be stored in the main electrical room or in another location identified in the closeout documentation.
+### Every revision shall carry a revision number and date on the cover, a list of the buses whose results changed, and a list of the labels to be replaced, and no label shall remain installed that carries a value a revision has superseded.
−# Warranty {toc}
+## Review and Re-Study Triggers {toc}
+### The report shall state the interval, indicated in the datasheet, at which the Owner is to have the study reviewed for accuracy, and the interval shall not exceed the five years NFPA 70E 130.5(G) permits.
+
```datasheet
−label: Analyst Warranty Period
−type: select
+label: Periodic Review Interval
+type: range
+unit: years
options:
− - "1 year from report issue"
− - "Through the project warranty period"
− - "Through the first periodic review"
−default: "1 year from report issue"
+ min: 1
+ max: 5
+ setpoints: [1, 2, 3, 5]
+default: 5
+constraint: max
```
−## The analyst shall warrant the analysis for accuracy at the time of issue, against the input data provided and the standards in force.
+### Five years is the longest interval NFPA 70E permits between reviews and the one nearly every program adopts, on a facility whose change procedures bring every trigger event to the responsible engineer as it happens; a shorter interval is the arrangement of a facility that is reconfigured often, that has no change procedure capturing electrical work, or whose utility reinforces its system on a schedule the Owner does not see, and it buys a label that is checked before the system has drifted from it. {note}
−## The analyst is not responsible for changes in field conditions, utility fault current, or protective device settings that occur after the study is issued; those are the Owner's responsibility under the periodic-review program.
+### The review shall confirm whether any trigger event has occurred since the study or its last review, shall re-run and re-label every bus a trigger event affects, and shall re-issue the report with the review date and the finding where no trigger event has occurred.
−## The Contractor shall warrant the physical installation of the labels — adhesion, location, and correspondence between label content and the report — for the project warranty period.
+### The report shall include a re-study trigger list, written for the Owner's operations staff, naming the events after which the Owner is to have the study updated before the affected equipment is returned to normal operation, and the list shall name at least the events indicated in the datasheet.
−## Labels that detach, fade, or are found to disagree with the report during the warranty period shall be replaced at no cost to the Owner.
+```datasheet
+label: Re-Study Trigger Events
+type: checkbox
+options:
+ - "Any event on the re-study trigger list of the short-circuit study"
+ - "Any event on the re-study trigger list of the coordination study"
+ - "A change to the setting of any device in the model"
+ - "Replacement of a protective device with one of a different make, frame, trip unit, or relay type"
+ - "A maintenance switch, interlock, or mitigation system added, removed, or found inoperative"
+ - "Replacement of equipment at a bus with equipment of a different configuration, enclosure, or gap"
+ - "A new operating configuration, tie, bypass, or parallel source"
+ - "A field condition found inconsistent with the model or the label"
+ - "Adoption of a mitigation recommendation"
+default:
+ - "Any event on the re-study trigger list of the short-circuit study"
+ - "Any event on the re-study trigger list of the coordination study"
+ - "A change to the setting of any device in the model"
+ - "Replacement of a protective device with one of a different make, frame, trip unit, or relay type"
+ - "A maintenance switch, interlock, or mitigation system added, removed, or found inoperative"
+ - "Replacement of equipment at a bus with equipment of a different configuration, enclosure, or gap"
+ - "A new operating configuration, tie, bypass, or parallel source"
+ - "A field condition found inconsistent with the model or the label"
+ - "Adoption of a mitigation recommendation"
+constraint: all_of
+```
+
+### Where any trigger event occurs, the updated study shall be run on the updated short-circuit model and the updated coordination settings for the affected portion of the system, and the labels at every affected bus shall be replaced under [[sync/equipment-labeling]] before that portion is returned to normal operation.
+
+### The re-study trigger list shall be included in the operation and maintenance documentation of the electrical system, and the Owner's change procedures for the electrical system shall name the responsible engineer to be notified when a trigger event occurs.
+
+### The arc-flash label inherits every trigger of the two studies beneath it and adds its own, and most of them are ordinary maintenance: a trip unit replaced with the one in stock and left at its shipping setting, a maintenance switch bypassed to stop a nuisance trip, a panel replaced with a deeper one. None of them look like a reason to commission a study, which is why the list is written for the operations staff in the words of the work they do, and why the label carries its date. {note}