Presented By: Allison Fritz, P. Eng. & David Hildebrand, P. Eng.

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Arc flash hazard poses a significant risk to electrical workers
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It is the law in Manitoba that employers must protect workers from injury due to arc flash hazard
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All workers at GO facilities are required to comply with the
GO Arc Flash Hazard safety program
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Important that all equipment and systems are designed to reduce the operational impacts of an arc flash hazard

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There are generally three types of electrical hazards: i.
Electrical shock ii.
Arc blast iii.
BURNS FROM ARC FLASH
An arc flash occurs when electrical current flows through the air and releases heat energy
Arc Flash Hazard is the total amount of heat energy exposed to a surface of the skin at a specified distance (measured in cal/cm 2 )
Arc flash events have a probability of occurring during interacting energized electrical equipment

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An Arc Flash Hazard is identified as follows:
◦ Incident energy (cal/cm 2 )
◦ Working distance
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Distance from the arcing source to the face or torso
◦ Flash protection boundary
 Distance from the arcing source to where the incident energy is 1.2 cal/cm 2

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Hazard Risk Category (HRC)
Hazard Risk Category
(HRC)
0
1
2
3
4
Dangerous
Incident Energy
1.2 cal/cm 2
4 cal/cm 2
8 cal/cm 2
25 cal/cm 2
40 cal/cm 2
Greater than 40 cal/cm 2

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Each Hazard Risk Category (HRC) has a list of personal protective equipment (PPE)
Modified PPE if work is unsafe
For example, while working on equipment that is HRC 4 (40 cal/cm 2 ) the following
PPE must be worn:
◦ Arc-rated long-sleeve shirt and pants
◦ Arc-rated arc flash suit jacket and bib-overalls
◦ Arc Rated Hood (face shield & hard hat)
◦ Safety glasses
◦ Hearing protection
◦ Safety footwear
◦ Rubber insulating gloves (proper voltage class)

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Manitoba Safe Work Bulletin No. 277 – Arc Flash
Hazards, August 2011
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◦ “ The employer must ensure that an arc flash hazard analysis is conducted for all electrical equipment to be worked on in an energized state, unless the following conditions are present:
 The circuit is rated 240 volts or less;
 The circuit is supplied by one transformer; and
 The transformer supplying the circuit is rated less than
125 kVA
The findings of the arc flash hazard analysis must be posted on the piece of equipment ”

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CAN/ULC-S801-2014 – Standard On Electric Utility Workplace
Electrical Safety for Generation, Transmission, and
Distribution
◦ “8.1.1 When workers are required to work in proximity to energized equipment above 50 V a.c., all potential sources of electric arc hazard shall be identified and risk assessed.”
CSA Z462-2015 – Workplace Electrical Safety
◦ Table 4A identifies tasks requiring PPE where arc flash risk is significant
IEEE 1584-2002 – IEEE Guide for Performing Arc-Flash Hazard
Calculations
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IEEE Paper entitled “ Arc Flash Calculations for Exposures to
DC Systems ” by D. R. Doan

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The Generation Operations (GO) Arc Flash Working Group was initiated late 2014 to implement an arc flash safety program
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Live work restriction directive was issued by the GO division management on April 21, 2015 (huge impact on operations)
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GO Arc Flash Working Group was able to develop assessment methods and tools based on the industry standards
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GO Arc Flash Safety Program is now successfully implemented and regular work has resumed

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Information sharing via Sharepoint site
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Arc Flash Safe Work Procedure
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Generation Operations Technical Bulletin
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Arc Flash Hazard Assessment eforms
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Arc Flash Labels

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Arc flash hazard labels are to be placed on each piece of equipment
Labels refer to the arc flash assessment via tracking number
Labels indicate the worst-case hazard risk category, flash protection boundary and working distance
Sample Label

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Risk of arc flash hazard can be reduced at the design stage with the following methods:
◦ Reduced fault currents
◦ Faster/better coordinated protection systems
◦ Arc detection systems
◦ Barriered primary circuits
◦ Maintenance/troubleshooting with door closed
◦ Load-break/horsepower-rated safety switches
◦ Arc-resistant switchgear
◦ System redundancy

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The risk of arc flash hazard can be reduced operationally with the following methods:
◦ DE-ENERGIZE!!!
◦ Identify flash protection boundary
◦ Wear appropriate arc-rated PPE
◦ Use temporary barriers & insulated tools
◦ Safe work procedures
◦ Worker training & awareness
◦ Use remote racking devices or insulated tools (ie. hot sticks)

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Assessments are completed in two parts
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◦ Energy Source Identification - Each exposed electrical energy source in the work area must be identified and qualified, including the voltage, upstream protective device, source transformer, etc.
Incident Energy Analysis – Each energy source must be analyzed to determine the maximum available incident energy that a worker would be exposed to if an arc flash event occurs. Two methods have been developed for incident energy analysis:
 Risk Based Assessments
 Incident Energy Calculations

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Incident Energy Analysis methods:
◦ Risk Based Assessments – for energy sources
240Vac and below, from sources less than 125kVA,
Risk = Probability x Severity x Frequency
◦ Incident Energy Calculations – For energy sources above 240Vac or 125kVA, engineering calculations are performed to determine the incident energy.
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PPE Requirements based on risk/quantified incident energy

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IEEE 1584 Empirical Method
◦ 208 V – 15,000 V, 3-phase, AC
◦ Available short circuit current from 700 – 106,000 A
◦ Arc gaps of 13 – 152 mm
Lee Method (IEEE 1584, Section 5.4)
◦ Theoretical, applies to all AC voltages, short-circuit current, and arc gaps
◦ 1-phase; multiply by √ 3 for 3-phase
◦ In air; multiply by 3 for arc-in-a-box (enclosure)
Doan Method (CSA Z462, Appendix D)
◦ Theoretical, applies to all DC voltages, short-circuit current, and arc gaps
◦ Identical to Lee Method; only difference is due to rounding of unit conversion

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◦ Equipment designation
◦ Tracking number
◦ Each energy source & associated calculation/PPE
◦ Identification of the highest hazard risk category, flash
◦ Reference documentation
◦ Authentication from the person who prepared the

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Assessment Tools:
◦ Breaker curve assessments
◦ Fuse curve assessments
◦ Minimum cable length assessments
◦ DC arc flash studies (most stations completed to-date)
◦ AC arc flash studies (four stations completed to-date)
◦ Equipment specific calculations including system short-circuit study

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Breaker curve assessments
◦ Example: Westinghouse, 100A, type BAB breaker, TCC curve shows HRC 3 for 600VAC

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Fuse curve assessments
◦ Example: Ferraz-Shawmut, 200A, type A4J fuse, shows HRC 2 for 250VDC

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DC arc flash studies
◦ Example – McArthur Falls Generating Station 250VDC System

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AC arc flash studies
◦ Example – Gen 1 &
Gen 2 model from
Pointe du Bois
Generating Station
Easy Power model

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Background
GO Arc Flash Program
Assessment Methods & Calculations
Conclusion & Key Points
◦ It is the law in Manitoba that employers must protect workers from arc flash hazard.
◦ De-energize where practicable.
◦ Use risk reductions methods at design stage and operationally.
◦ Conduct hazard risk assessments, wear appropriate arc-rated PPE, establish flash protection boundary.

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Possible Discussion Topics:
◦ Arc Flash Personal Protective Clothing
◦ Arc Flash Assessment Methods
◦ Arc Flash Calculations
◦ TCC curve Analysis
Questions?
Thank you!