Arc_Flash_Understanding_and_Preventing.pdf

7/27/2019 Arc_Flash_Understanding_and_Preventing.pdf

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Make the most of

your energy

Make the most of

your energySM

Electrical Arc Flash Safety &

Risk Management


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Schneider Electric 2

Summary of Topics Covered

Types of major electrical faults

Fault characteristics

Arc flash injury statistics

Requirements of NFPA 70E, OSHA, NEC,IEEE 1584

Equipment labeling for arc flash hazard

Establishing an electrically safe work condition


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Summary of Topics Covered

Boundary distances and PPE requirements

Methods of determining flash hazard levels

Limits of approach

PPE hazard risk categoriesProducts and services for hazard mitigation


4/50Schneider Electric 4

Square D Arc Flash Video Its a Matter of Your Safety

The explosive forces of an Arc Flash
http://a%20-%20its%20a%20matter%20of%20your%20safety.wmv/



What is an Arc Flash?

A hazard beyond shock and electrocu t ion

NFPA 70E says an arc flash

hazard is:

A dangerous conditionassociated with the

possible release of energycaused by an electric arc

NFPA 70E 2009 article 100 - Definitions



Two Types of Major Electrical Faults Can Occur

Bolted faults

Low impedance and high current

Energy is contained by the conductor (bus or cable)

Cleared quickly by circuit breakers or fuses

Arcing is confined within the circuit breaker or fuse

Usually no damage to equipment

Relatively low safety risk to personnel

Arcing faults

High impedance (air) results in lower current

Persist longer and propagate

High release of heat and blast energy

Are very destructive and dangerous to personnel



500 KV Switch


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Causes of Bolted and Arcing Faults

What causes these types of faults?

Bolted faults (low impedance and high current)

Commonly caused by Improper connections after maintenance

Installation errors

Arcing faults (high impedance, lower current) Commonly caused by

Careless cover or device removal

Foreign object (tool) dropped into equipment

Misalignment of moving contacts (parts failure)

Dirt contamination or dielectric breakdown

Entry of foreign body (rodent, snake, squirrel)


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Electrical Arc Facts

Arc is electric current passing through air

Shock potential from potential contact with arc

Temperature of arc plasma center often reaches 35,000Degrees Fahrenheit

Radiated heat burns

Pressure wave generated from arc Impact to hearing, etc (sound levels can exceed160 dB)

Gaseous copper is 67,000 times its solid volume

Molten metal expelled from equipment at high speed (~700 MPH)

Extreme pressures (thousands of pounds per square foot).

Arc fault results from something wrong or out of place


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What a 480 volt Arcing Fault Looks Like


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Some Arc Flash Injury Statistics

Five to ten arc flash explosions occur in electricalequipment every day in the United States, according tostatistics compiled by Cap-Schell, Inc., a Chicago-based

research and consulting firm that specializes in preventingworkplace injuries and deaths.

Injuries from arc flash events range from minor injuries tothird degree burns and potential death due to the energyreleased.

Other injuries include blindness, hearing loss, nervedamage, and cardiac arrest.

The average cost of medical treatment for survivors ofserious arc flash injuries is $ 1,500,000

Total costs including litigation can be $8M - $10M


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Results of an Arc Flash

Other non-human consequences

Downtime

Lost revenue

Loss of product

Equipment damage

Regulatory impact

OSHA citation and fines


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Transformer


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Whats Changing in the Industry?

Attention to arc flash costs and prevention

Impact to large manufacturers drove attention to arc

flash hazards

Recognition of unsafe work practices: energized

work

Changes to NEC & NFPA 70E

New IEEE 1584 Standard for Arc Flash Hazard

Calculations

Enforcement by OSHA


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NFPA70 (NEC) NFPA70E-2009 OSHA 29 CFRPart 1910

IEEE 1584 -2002

Governs ElectricalInstallations

Governs EmployeeWorkplace Safety

OSHA Standards(Iowa Shown)

Guide for PerformingArc Flash Hazard

Calculations

Applicable Documents


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New Requirements on Facilities

NFPA 70E and NEC state that facilities must

provide:

Safety program with defined responsibilities

Analysis for arc flash hazard degree

Training for workers

Personal protective equipment (clothing) for workers Tools for safe work

Warning labels on equipment

Resul t : Faci li ties must take steps to comply.


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Requirements: 2008 NEC

110.16: Electrical equipment, such as switchboards,

panelboards, industrial control panels, meter socket

enclosures, and motor control centers, that are in other

than dwelling occupancies, and are likely to require

examination, adjustment, servicing, or maintenance while

energized shall be field marked to warn qualified persons

of potential electric arc flash hazards. The marking shall

be located so as to be clearly visible to qualified personsbefore examination, adjustment, servicing, or

maintenance of the equipment.

Warning fo r awareness , to p repare for fu ture wo rk

Field marked - not marked by m anufacturer

No ment ion o f values - only warn ing of hazard

References NFPA 70E, ANSI Z535.4


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NEC 110.16NEC 110.16


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Example Equipment Label

Il lustrates m inimum requ irement. This is an example,

not a recommendat ion.


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Inadequate Labeling Example


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Examples - Arc Flash Labels with Data Values


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Employer shall provide practices

Employer shall provide training

Employee shall implement practices

The responsibilities as defined in the codes and standards

Responsibilities for Safety Compliance


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Who is a Qualified Person ?

NFPA 70E and the National Electrical Code (NEC)define a qualified person as:

One who has skills and knowledge related to theconstruction and operation of the electricalequipment and installations and has received

safety training to recognize and avoid the hazardsinvolved

Training on the hazards is required by definition

NFPA 70E 2009 Article 100 - definitions


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OSHA 29 CFR 1910.333

Safety related work practices shall be

employed to prevent electric shock or otherinjuries resulting from either direct orindirect electrical contacts when work is

performed near or on equipment of circuitswhich are or may be energized

OSHA c ites NFPA 70E for compl iance requ irements


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OSHA 29 CFR 1910.333

Live parts to which an employee may beexposed shall be de-energized before the

employee works on or nearthem, unless theemployer can demonstrate that de-energizingintroduces additional or increased hazards or is

infeasible due to equipment design oroperational limitations.

The fundamental requ irement is to de-energize!

Whenever you al low work to be done energized,

you take a risk .


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Work Involving Electrical Hazards

Justification for Work (NFPA 70E 2009 article 130.1 (A)

Energized electrical conductors and circuit parts to which anemployee might be exposed shall be put into an electrically safe

work condition before an employee works within the LimitedApproach Boundary of those conductors or parts.

(1) Greater Hazard. Energized work shall be permitted where the

employer can demonstrate that de-energizing introduces additional orincreased hazards.

(2) Infeasibility. Energized work shall be permitted where the employercan demonstrate that the task to be performed is infeasible in a de-energized state due to equipment design or operational limitations.

(3) Less than 50 volts. Energized electrical conductors and circuit partsthat operate at less than 50 volts to ground shall not be required to be de-

energized


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OSHA 29 CFR 1910.335

Employees working in areas where there arepotential electrical hazards shall be provided with,and shall use, electrical protective equipment that isappropriate for the specific parts of the body to be

protected and for the work to be performed.

Not ice that OSHA does not speci f ica lly ment ion

calcu lat ions or NFPA 70E. However, sin ce NFPA

70E is a recognized, publ ish ed standard available

to the industry , OSHA w i l l always c i te using

requirements o f NFPA 70E.

Personal Protective Equipment


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Limits of Approach

NFPA 70E 2009 Annex C, Fig. C.1.2.4

Flash protection boundary:

An approach limit at a distancefrom exposed live parts withinwhich a person could receive asecond degree burn if an electricarc flash were to occur. (NFPA70E 2004)

It is general ly accepted that a second

degree burn resul ts from expo sure of

inc ident energ y o f 1.2 cal/cm2

Fl h P t ti B d


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D

Dfb

Flash Protection Boundary

a distancefrom exposedlive parts

within which aperson couldreceive asecond degreeburn


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Incident Energy

The amount of energyimpressed on a surface, a

certain distance from thesource, generated during anelectrical arc event.

Incident energy is measured incalories/cm2 or Joules/cm2.

The incident energy defines the PPEcategory required

NFPA 70E 2009 Article 100 - definitions

I id t E


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Incident energy is energyimpressed on this surface

a working distance, D,

from the electrical arc

source.

D

Incident Energy

D t i PPE H d Ri k C t


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Determine PPE Hazard Risk Category

0 N/A Untreated cotton, wool, rayon or silk, or blends of these materials with a fabricweight of at least 4.5 oz/yd2

1 4 Arc Rated FR shirt & FR pants or coverall

2 8 Arc Rated FR shirt & FR pants or coverall

3 25 Arc rated FR shirt & pants or coverall, and arcflash suit selected so that the system arc ratingmeets the required minimum.

4 40 Arc rated FR shirt & pants or coverall, and arc

flash suit selected so that the system arc ratingmeets the required minimum.

Note that melt-able fabrics and other similar synthetics are never permitted

Category Cal/cm2

Clothing Description

Source: NFPA 70E 2009


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PPE Examples

Category 2 PPE Category 4 PPE

Photos copyright 2005 Oberon Company


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Methods of Determining Incident Energy and

Hazard Risk Category IEEE 1584

Hand calculations (not recommended)

Shortcut calculations

Calculations using spreadsheet

Calculations by consulting engineersTables in NFPA 70E

Schneider / Square D consulting services

Published values from manufacturers tests

Commercial software


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NFPA 70E Table (example)

* - a double-layer switching hood or wraparound face shield and hearing

protection are required for this task in addition to other Category 2requirements

NFPA 70E 2004, Table 130.7(C)(9)

Note: Tables are a convenient way to know the hazard if calculationshave not been done. However, data in tables tends to be conservative

Take care to follow footnotes when using the tables

TaskHazard/Risk

Category

V-rated

gloves

V-rated

tools240 V PanelboardWork on energized electricalConductors and circuit parts

1 Y Y

600 V Panelboard

Work on energized electricalConductors and circuit partsparts

2* Y Y


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Overcurrent Protection and Arc Flash Analysis

Why is a circu i t breaker or

fuse always considered in

arc f lash analysis?

1. The circuit breakeror fuse clears the

circuit to stop thearcing.

2. It determines howfast the circuit is

cleared.

energy = volts x amps x time

faster clearing time = lower energy


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Which device clears the arcing fault?

Arc originates here

Must rely on this device to clearthe arcing fault

Arc maypropagate to

the supplyside of alldevices inthe sameenclosure

Arc propagates to here


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Once the Calculations are Done...

Workers are required to wear appropriate

Personal Protective Equipment (PPE)

What workers wear depends upon the

incident energy exposure level...

And the specific task to be performed


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Important Changes in NFPA 70E 2009

Article 130.3 Exception Number 1An arc flash hazard analysis shall

not be required where all of the following conditions exist:

The circuit is rated 240 volts or less

The circuit is supplied by one transformer The transformer supplying the circuit is rated less than 125 kVA

Article 130.3 Exception Number 2 The requirements of 130.7(C)(9),

130.7(C)(10), and 130.7(C)(11) shall be permitted to be used in lieu of

a detailed incident energy analysis

FPN Number 1 Improper or inadequate maintenance can result in increased

opening time of the overcurrent protective device, thus increasing the

incident energy

Article 130.3 (C) -- Equipment shall be field marked with a label

containing the available incident energy or required level of PPE.



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130.3 Arc Flash Hazard Analysis -- The arc flash hazard analysis shall

be updated when a major modification or renovation takes place. It

shall be reviewed periodically, not to exceed five years, to account for

changes in the electrical distribution system that could affect the resultsof the arc flash hazard analysis.

Article 130.3 (C) Effect of maintenance on arc flash protection

boundary and personal protective equipment - Proper maintenanceof overcurrent protective devices is required in order to successfully

predict the degree of hazardous energy to which a worker may be

exposed under arc flash conditions.

Note: NFPA 70E cites NFPA 70B and equipment manufacturers

recommendations for proper maintenance requirements and

intervals.


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Article 205.2 Single Line Diagram A single line diagram where

provided for the electrical system shall be maintainedArticle 205.3 General Maintenance Requirements Overcurrent

protective devices shall be maintained in accordance with the

manufacturers instructions or industry consensus standards

Article 210.5 Protective Devices Protective devices shall bemaintained to adequately withstand or interrupt available fault

current.

FPN: failure to properly maintain protective devices can have an

adverse effect on the arc flash hazard analysis incident energy values

S


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Summary

Arc Flash is a significant electrical safety concern

Industry standards are in place to address the issue

Require selection and use of PPE based on Flash Hazard

analysisBut PPE is to be a last line of defense!

System design considerations can reduce the potential exposure

to arc flash #1 goal: No energized work

#2 goal: If work must be done energized, at least let it be doneon a system where the hazard level has been reduced

See NFPA 70E 2009 Annex O Safety Related Design Requirements - for

recommendations on designing for safety


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Products and Services for Hazard MitigationProducts and Services for Hazard Mitigation

New Products to Reduce Arc Flash Hazard


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Arc Terminator (MV)Arc Terminator (MV)

Low Arc Flash

Circuit Beakers

Low Arc Flash

Circuit Beakers

MasterClad

AR Arc Resistant

Switchgear (MV)

MasterClad

AR Arc Resistant

Switchgear (MV)

Remote Racking (MV)Remote Racking (MV)

New Products to Reduce Arc Flash Hazard

IR Viewing WindowIR Viewing Window

Retrofit & UpgradeRetrofit & Upgrade


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The conversion with the

modification and/orenhancement of switch-

gear by installing a new

breaker and cell into the

existing cubicle.

All new cubicle racking

mechanism, primary and

secondary disconnects.

Eliminates the need for

obsolete or unavailable

spare parts.

MASTERPACT

RetrofillLV Circuit Breaker

Engineering Services


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Engineering Services

Provide required electrical arc flash analysis

Update electrical one-line diagram Update system short circuit study

Update system coordination study

Collect system data and perform arc flash analysis Identifies over-dutied equipment

Identifies code violations

Identifies dangerous conditions(high incident energy potentials)

On-Site Preventive Maintenance


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XX Periodic inspection and maintenance to help extendPeriodic inspection and maintenance to help extendequipment life and ensure operating efficiencyequipment life and ensure operating efficiency

XX Comprehensive mechanical and electrical testing to ensureComprehensive mechanical and electrical testing to ensure

proper functional operation including:proper functional operation including:OO Cable testing, relay and metering calibrationCable testing, relay and metering calibration

OO Circuit breaker testing, transformer testingCircuit breaker testing, transformer testing

OO Infrared testing, ATS testing/troubleshootingInfrared testing, ATS testing/troubleshooting

XX Also available:Also available:

OO Custom service agreementsCustom service agreements

OO FacilityFacility--wide outage managementwide outage management

XX Services available for Square D and nonServices available for Square D and non--Square DSquare D

equipmentequipment

Arc Flash Safety Training


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Arc Flash Safety Training

Training is required by the NFPA 70Estandards

Square D course number DPEC 111

Eight hour course for electrical workers andtheir supervisors -- instructors are experiencedand OSHA qualified

Meets all requirements of NFPA 70E for safety

trainingElectrical workers are not considered qualified

without specific training on the hazards

Training available at or near plant or facilitylocation

To learn more about this topic


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o e o e bo t t s top c

Square D Services website

www.squared-services.comArticles in trade magazines and IEEE transaction papers

NFPA website

www.nfpa.orgIEEE website

www.ieee.org

OSHA website

www.osha.gov


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Thank YouThank You

Larry LongLarry Long

Square D ServicesSquare D Services(703) 885(703) 885--22752275