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STATE OF OHIO

DEPARTMENT OF TRANSPORTATION

SUPPLEMENTAL SPECIFICATION 825

ARC-FLASH HAZARD CALCULATIONS AND EQUIPMENT LABEL

July 15, 2016

825.01 Description

825.02 References

825.03 Materials

825.04 Calculations

825.05 Construction

825.06 Method of Measurement

825.07 Basis of Payment

825.01 Description. This item consists of calculating the arc flash hazard for installed new or existing

electrical enclosures, providing documentation of the calculations, and applying the appropriate external

arc flash hazard equipment label to meet established industry standards.

825.02 References. The following industry standard documents are referenced in this specification:

IEEE Std 1584-2002 Guide for Performing Arc-Flash Hazard Calculations

IEEE Std 141-1993 Recommended Practice for Electric Power Distribution for Industrial Plants

NFPA 70 National Electrical Code, as adopted by the State of Ohio

NFPA 70E Standard for Electrical Safety in the Workplace, 2015 Edition

825.03 Materials. Ensure that material for the arc flash hazard equipment label conforms to ODOT

C&MS 730.18, Reflective Sheeting Type F. The sheeting color shall be safety orange, 4 inches high and

six inches wide. A sample image of a typical label is given below.

825.04 Calculations. Deliver to the Engineer three (3) copies of the completed calculations, printed

and stamped by an engineer licensed to practice in the State of Ohio. Provide the same as PDF files on a

standard digital medium. Provide an itemized inventory of the installed electrical devices used in the

calculations, including distribution transformer nameplate data and overcurrent device time-current

curves. Percent impedance value for distribution transformers may be obtained from catalog sheets.

Record distances between devices when such distances are used in the calculations. Provide, on a standard

digital medium, digital photographs of each electrical device used in the calculations.

Perform calculations that conform to IEEE 1584-2002, as follows:

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Part 5.1. Ensure that calculations are made using a predicted three-phase bolted fault (Ibf) current

in the range of 700A to 106kA. Generally, the power-company-side system impedance is not

available and is ignored. Cable impedance from the source to the fault point should be included.

Single-phase faults on 3-phase systems may be analyzed using a predicted fault current identical

to the bolted three-phase fault, providing conservative results.

The bolted fault calculation method for low-voltage systems in Part 4.7 of the IEEE “Red Book”

(IEEE Std. 141-1993 Recommended Practice for Electric Power Distribution for Industrial

Plants) or an equivalent industry-standard method (including commercial arc-flash calculation

software) may be used. According to the “Red Book,” 1) a balanced three-phase system will never

produce a line-to-line fault current exceeding 87% of Ibf, and 2) a solid-grounded-neutral system

will not produce a line-to-ground fault exceeding Ibf by more than a small percentage.

Single-phase systems may be analyzed using similar methods. Single-wire impedance values from

wire manufacturers may be used.

NEC Chapter 9 Table 9 lists impedance for one-way, three-phase cables. The impedance is slightly

different for a single-phase circuit. The formula for total (two-way) wire impedance is:

Z = k*ZTable9

Where k = 2 for single-phase loads

k=1.73 for 3-phase loads

ZTable9 is the impedance given by NEC Chapter 9 Table 9.

Utilize time-current curves for actual installed protective devices (fuses and/or circuit breakers)

when calculating arc durations. For lighting control centers, the protective device will often be the

power-company Type K or Type T expulsion fuse on the distribution transformer primary.

Part 5.2. In calculating the arcing current, unless specified otherwise in the Plans, use 13mm

(1/2-inch) as the typical conductor gap for electrical construction conforming to ODOT C&MS

625 items. Use a K value chosen for “box configurations.”

Part 5.3. In calculating the incident energy, use 305mm (12 inches) as the typical working distance

for highway lighting equipment conforming to ODOT C&MS 625 specifications. Perform

calculations using three distinct portions of the overcurrent device time-current curve:

1. Instantaneous

2. Short-Time

3. Long-Time.

Part 5.6. If current-limiting fuses feed the enclosure for which calculations are being made, the

equations of Part 5.6 may be used.

Based on the calculated incident energy, consult NFPA 70E to determine the required PPE for

energized work near or within the subject enclosure.

825.05 Construction. Permanently mark the label using standard sign sheeting silk screen process,

such that each enclosure label is unique, with integral text and check box marks. Do not use marking pens,

paint, or other means to mark the label. Ensure the label contains the following information as a minimum:

1. Arc Flash Boundary (in inches or feet)

2. Incident Energy (in cal/cm^2)

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3. Arc Flash PPE Category

4. Work Distance (inches)

5. Minimum Arc Rating of Clothing (in cal/cm^2)

6. Nominal System Voltage

7. Date of Calculation

8. Equipment ID

9. A checkbox field of required PPE (Personal Protective Equipment) items from NFPA 70E.

Clean, degrease and dry the attachment area. Apply the label to the enclosure according to NEC Article

110 requirements.

825.06 Method of Measurement. Arc Flash Calculation and Label will be measured by the number

of units, EACH, complete, with deliverables accepted and label installed, for each separate installed

electrical enclosure with voltage levels 50 volts or over.

825.07 Basis of Payment.

ITEM 625 Arc Flash Calculations and Label, (location) (Each)

825.08 Sample Label. A sample label showing the typical fields used is given below.

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Designer Note: This Supplemental Specification should be referenced from a Plan Note. The location of each electrical

enclosure is noted in the line item description. The designer determines which enclosures require labels,

per NFPA 70E. On more complex jobs, such as tunnels or large bridges that contain multiple enclosures

not paid for individually, this Supplemental Specification may be used as a reference.

This item may be used on any completely operational electrical installation, both newly-constructed and

old work. It is used to provide permanent labels for outdoor electrical enclosures such as lighting and

signal power service, and control centers, but may be referenced for other electrical enclosures, including

those located indoors. Arc Flash Hazard Equipment Labels are required by NFPA 70E, 2015 Edition, Part

130.5(D). These labels provide ready identification of arc flash hazards and appropriate PPE for

maintenance personnel before they access an electrical enclosure. The calculations for determining the arc

flash hazard level require a qualified engineer.

Labels for ODOT-maintained installations may be provided by the ODOT Sign Shop, 1606 West Broad

Street, Columbus Ohio 43223. If this is desired, the Designer must indicate so in the Plan Note. Otherwise,

the Contractor is responsible for obtaining the label, made from what is commonly known as “Engineer

Grade” sign sheeting.