bluebonnet electric cooperative

Bluebonnet Electric Bluebonnet Electric CooperativeCooperative

Arc Flash Hazard Mitigation

Thomas Ellis, PEManager of Engineering

Serves 81,000 meters acrossServes 81,000 meters across11,000 miles of power lines within11,000 miles of power lines within14 Central Texas Counties14 Central Texas Counties

What is Arc FlashWhat is Arc FlashArc Flash is a massive energy

dischargeSimilar to the arc obtained during

electrical weldingInitiated by creation of a conducting

path or breakdown in insulationSustained by the establishment of a

highly-conductive plasma Arc fault current is often lower than

available bolted fault current

Arc Flash EnergyArc Flash EnergySystem VoltageFault current

magnitudeDuration of Fault Enclosures

magnify blast and energy transmitted ◦ 2-12 times

greater energy

Incident EnergyIncident Energy

Incident Energy measured at the arc potential to the employees face and/or torso

cal/cm^2

Incident EnergyIncident EnergyIncident Energy

(cal/cm²) Degree Burn

1.2 2nd degree burn to bare skin

4 Ignite a cotton shirt

8 3rd degree burn to bare skin

Shows the damage that incident energy can impart.

Arc Flash EffectsArc Flash EffectsExtreme heat,

pressure waves, and sound waves◦ 35,000 degrees

Fahrenheit◦ Molten Metal,

Shrapnel, and Vapor◦ Expansion rate

40,000-1◦ Intense light

Burns Punctures Concussion Capable of causing

severe/fatal injuries

Arc Flash HazardsArc Flash HazardsPersonnel have exposure to electric

arcs:◦When working on or near exposed

energized electrical conductors or circuit parts.

◦When interacting with electrical equipment where an electric arc could occur.

◦Under normal conditions, equipment that is installed and maintained is not likely to pose an arc flash hazard if an personnel are not interacting with the equipment.

Racking BreakerRacking Breaker

National Electric Safety Code National Electric Safety Code (NESC) - 2007(NESC) - 20072007 code published August 1, 2006410.A.3

◦“Effective as of January 1, 2009, the employer shall ensure that an assessment is performed to determine potential exposure to an electric arc for employees who work on or near energized lines, parts, or equipment.” Potential exposure greater than 2 cal/cm^2

410-1, 410-2 ATPV less than anticipated arc energy, <1000V arc hazard analysis

National Electric Safety Code National Electric Safety Code (NESC) - 2012(NESC) - 20122012 code published August 1, 2011410-A3

◦Perform a detailed arc hazard analysis ◦Alternative – use clothing system tables

410-1- independent of fault current 50V - 1000V

410-2 1.1kV – 46kV

410-3 46.1kV – 800kV

Arc Flash HazardsArc Flash HazardsBBEC identified arc hazards over

2 cal/cm².Proactive approach to limit

employee arc exposure thru:◦Engineering controls◦Work rules◦Personal Protective Equipment

ObjectivesObjectivesReduce potential for personnel

injury due to arc flash incidents Electrically safe?

◦Identify hazards◦Provide guidance for performing

required duties on or near energized lines and equipment

◦Determine the best possible PPETo comply with NESC-2007/NESC-

2012

Arc Flash AnalysisArc Flash AnalysisWhat is Arc Flash Analysis?

◦A study to determine the anticipated level of incident energy personnel would be exposed to Conducted for the purpose of:

Injury prevention Determination of the following:

Safe work practices Arc flash protection boundary Effective arc rating of clothing systems Appropriate levels of PPE Training for personnel on hazards of arc flash Appropriate tools NFPA 70E, IEEE 1584

Arc Flash Calculation Arc Flash Calculation VariablesVariablesVoltageFault current in AmpsDuration of Fault in Seconds or

Cycles◦Protective device clearing time

Arc Gap LengthWorking Distance to Employee

◦Arc to employee-assumptions vary depending on task

Open Air versus Enclosed Space (“Arc in a Box”

Arc Flash AnalysisArc Flash AnalysisArc Flash Boundary

◦Personnel inside the arc flash boundary are required to wear the standard work uniform when: Performing work Assisting in work Observing work (1.2 cal/cm^2)

Arc Flash AnalysisArc Flash AnalysisSystem normal

operating mode◦ Non-Reclose◦ Abnormal

operating mode requires additional caution

Proper documentation of changes

Reliable update process

Arc Flash AnalysisArc Flash AnalysisProper

equipment operation

Coordination study◦ Proper equipment◦ One shot

Adherence to maintenance plan

Identified Work Identified Work Inside a substation between the

transformer low side and the outgoing primary feeders.

On energized conductors or circuit parts over 600 volts.

On energized conductors or circuit parts under 600 volts.

To connect and disconnect meters.

Inside SubstationInside SubstationBoundary – inside the fence

◦ No rubber gloving Incident energy values may be excessive, the

standard work uniform will not provide effective AR protection during rubber gloving procedures.

Employees shall use a 15’ switch stick or a telescoping station stick to maintain a minimum of 8’ from the potential arcing source If under extreme conditions, an 8’ working distance cannot be maintained, a hot stick barrier (safety shield meeting ASTM F2522 – 05 standards) and an arc rated face shield shall be worn to provide extra protection against arc flash impacts

.

Energized equipment over Energized equipment over 600V600VBoundary – 15’Non-recloseRubber gloving

15” working distanceHot sticks

OH 8’ stick, 6’ working distance

URD 6’ stick 4’ working distance

Energized equipment under Energized equipment under 600V600VBoundary – 15’Three Phase

Enclosures◦ Diagnostics only

8’ hotstick 8” probe

Single Phase Enclosures◦ 15” working

distance

MetersMeters

Boundary – 15’Self contained

◦ Meter pullers◦ Diagnostics

8” probes

Hazard Identification and Hazard Identification and Risk AssessmentRisk AssessmentEvaluate jobsiteIdentify hazardRisk reduction

◦ Engineering controls

◦ Work practices◦ PPE

Safe Work Practices Safe Work Practices Equipment Operation

◦ Unknown conditionsSwitching and

Tagging◦ Verify/Authorize orders

Non-Reclose (HLTG)◦ Normal mode

Cover-up◦ Properly rated & applied

URD ◦ 4 feet minimum

Remote SwitchingRemote SwitchingWhen applicable,

SCADA operations shall be used to remotely operate switches. Remote operation of switches will reduce, if not eliminate, employee related arc flash hazards.

Standard Work UniformStandard Work Uniform8.7 cal/cm^2Shirt 8.7 cal/cm^2Pants 20 cal/cm^2Additional items

◦ Coveralls 20 cal/cm^2

◦ Face shield 12 cal/cm^2

◦ Balaclava 47.9 cal/cm^2

◦ Hood 40 cal/cm^2◦ Ear Arc Plug

ResponsibilitiesResponsibilitiesManagement

◦Responsible for initiating, overseeing, reviewing and updating a hazard recognition program to identify arc hazards and controls.

◦Responsible for communicating and training employees on identified arc hazards.

◦Responsible for implementing and enforcing the arc hazard implementation plan and for regularly reviewing and updating the program an necessary to ensure all arc hazards have been effectively identified and abated.

◦Responsible for budgeting necessary funds to ensure compliance.

ResponsibilitesResponsibilitesSupervisors, Foreman and Lead

Technicians◦ Identifying arc hazards and working with

management to develop processes and or procedures to minimize and/or eliminate the hazards.

◦ Ensuring employees have received necessary arc hazard training.

◦ Ensuring only qualified employees work on or near equipment with potential arc hazards.

◦ Enforcing the arc hazard implementation plan requirements including work rules and PPE.

ResponsibilitiesResponsibilitiesEmployees

◦Identifying arc hazards and working with management to develop processes and or procedures to minimize and/or eliminate the hazards.

◦Following work rules and wearing the appropriate FR clothing and other PPE as required.

TrainingTrainingEmployees will receive arc flash

training initially and every 3 years. Training will include but not be limited to:◦– Electric arc hazards◦– Identified work practices with arc hazards.◦– Engineering controls to minimize arc

exposure◦– Work rules required to minimize arc

exposure.◦– PPE use, care and maintenance

Safety RulesSafety RulesThe arc flash implementation plan

does not eliminate any existing safety rules or procedures.

All employees are required to follow established safety rules when working on or near energized lines and equipment.

All other work must be evaluated for arc hazards before the start of work.