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Arc Flash Hazard MitigationAnalyse, Maintain, Mitigate.

E3 Calgary – September 16, 2014

Dean Wiersema

What is an Arc Flash Hazard? - Definition (Z462-12) “A dangerous condition associated with the possible release of energy caused by an electric arc.”

> An arc flash hazard can exist when energized electrical conductors or circuit parts are exposed or are within equipment in a guarded or enclosed condition, if a person is interacting with the equipment in a manner that could cause an electric arc.

> Under normal operating conditions, enclosed energized equipment that has been properly installed and maintained is not likely to pose an arc flash hazard.

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Why is an Arc Flash Hazard a concern?

There are several consequences of an Arc Flash incident.

Depending on the severity of the event, Arc Flash can cause>Downtime>Lost Revenue>Equipment Damage>Large Fines>Individual Legal Liability>Serious Injury, or Death

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Why is an Arc Flash Hazard a concern?

The explosive nature of Arc Flash events can cause death or serious injuries.

Types of Arc Flash Injuries>External Burns>Internal Burns>Loss of Sight>Lacerations>Hearing Loss>Internal Injuries

- Concussion- Collapsed Lungs

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You must understand and manage your Arc Flash incident

risksIt is your responsibility to ensure risks are identified and

appropriate mitigation is applied.

What causes an Arc Flash Incident?

Incidents are either caused by human error/negligence, or through some equipment/distribution failure

Human Errors or Negligence include>Tool contacts a live conductor>Insertion or removal of

components>Lack of Maintenance>Test instrument misapplied

Equipment or Distribution Failures include>Equipment linkage failure>Contact misalignment>Insulation failure

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What should be done to ensure Arc Flash risks are being managed?

Analyse, Maintain, and Mitigate.

AnalysisKnow the Incident Energy Level of your Equipment.>Conduct an arc flash hazard

analysis of the electrical distribution equipment and post arc flash energy levels and arc flash boundary dimensions- See CEC Part I Rule 2-306

and CSA Z462-12 Clause 4.3.5.4

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What should be done to ensure Arc Flash risks are being managed?

Analyse, Maintain, and Mitigate.

How is Arc Flash Analysis conducted?1. Collect system and installation

data (Single Line)2. Determine system modes of

operation (Tie Breakers, Standby power etc)

3. Determine bolted fault currents (current flowing through the conductor)

4. Determine arc fault currents (Current flowing through the impedance of the arc)

5. Identify protective device characteristics and arc duration

6. Document system voltages and classes of equipment

7. Select working distances 8. Determine incident energy 9. Determine flash boundary10.Mitigate

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What should be done to ensure Arc Flash risks are being managed?

Analyse, Maintain, and Mitigate.

MaintenanceReduce the likelihood of an event.>As noted in the definition of

Arc Flash. Equipment that has been maintained has little chance of causing an Arc Flash- Z463

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What should be done to ensure Arc Flash risks are being managed?

Analyse, Maintain, and Mitigate.

10*Source: Hartford Steam Boiler Insurance Company)

77% of electrical equipment breakdown causes could be reduced by having electrical preventative maintenance performed*

What should be done to ensure Arc Flash risks are being managed?

Analyse, Maintain, and Mitigate.

MitigationHow do we Mitigate the risk levels?>Look at the 3 things that

make up Incident Energy- Fault Current- Time- Distance

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Why is Arc Flash mitigation necessary?

How do you feel about sustaining a “survivable” injury?

MitigationZ462-12, S4.3.7.1> The PPE requirements are intended

to protect workers from arc flash and shock hazards. While some situations could result in burns to the skin, even with the protection selected, burn injury will likely be reduced and be survivable. Because of the explosive effect of some arc events, physical trauma injuries can occur. The PPE requirements do not address protection against physical trauma other than exposure to the thermal effects of an arc flash.

> PPE is supposed to be your last line of defense.

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Hierarchy of Risk MitigationThe only safe electrical system is a de-energized system. Everything else is about risk mitigation.• Minimize exposure• Minimize severity

MitigationSeveral ways to manage risk (listed from least to most effective)> Personal Protective Equipment

- last line of defense

> Administrative Controls - regulate risk

> Awareness - reveal risk

> Engineering Controls - manage & control risk

> Elimination - remove risk

Engineering Controls - main focus for Arc Flash Mitigation

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What are some Engineering Controls for Arc Flash Mitigation?

Arc Flash mitigation systems exist in many forms. Most do not address all the issues that develop as a result of an arcing fault.

Questions that need to be answered> Is the arc fault mitigation system

reliable?- How does it prevent inappropriate

operation?

> Operational Speed- How fast can it extinguish the

uncontrolled arc?- Where does it disperse the energy?- What does it do with the upstream

protective devices/breakers?- Is there damage to the equipment?- How much damage occurs?- Can I get back up and running

quickly> How much does it protect

operational personnel?- PPE levels for maintenance as

determined by arc flash study

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Relay based:ZONE SELECTIVE INTERLOCKINGObjective:

•To trip the breaker closest to fault without time delay and maintain coordination.

Pros:•Can provide good coordination•Use of standard protection relays•Applicable to MV and LV systems

Cons:•May not provide desired AF reduction•Application intensive for some breakers

Additional considerations!

Speed determined by relay and breaker operation(Typical LV speeds: ~150ms (Breaker + Relay)

(Typical MV Speeds:~100ms (Breaker + Relay)

Can reduce PPE level for personnel to Cat 4 or below (Arc Flash Study Required)

•Equipment damaged recovery time dependant on fault magnitude

•Good isolation of fault

•Cost can be small when using relays with ZSI feature

Relay Based:BUS DIFFERENTIAL RELAY PROTECTION (87B)

Objective:•Arc fault reduction thru full bus protection

Pros:•Protection thru wide variety of low cost digital relays•Cons:•May not perform well in all situations. Ie internal faults•Challenges for complex bus arrangements•Less discreet than ZSI, may trip all breakers•Extremely expensive for LV applications

Additional considerations!

Speed determined by relay and breaker operation(LV speeds: ~ 150ms (Breaker + Relay)

(MV Speeds: ~100ms (Breaker + Relay)

•Can reduce PPE level for personnel

• Arc Flash Study Required

•Equipment damaged recovery time dependant on fault magnitude

•Cost can be higher than ZSI.

Arc Flash Maintenance Switch Objective:•Temporary reduction in incident energy thru lower instantaneous trip settings

Pros:•Lower PPE requirements•Cons:•Temporarily changes system coordination may interfere with other protective functions.•Requires normal and reduced trip settings•Possibility of fault propagation must be considered.

Additional considerations!

•Speed determined by relay and breaker operation (MV AND LV)

•Can reduce PPE level for personnel

• Arc flash study required.

•Equipment damaged recovery time dependant on fault magnitude and the position of the switch

•Operational implementation concerns

•Cost is small

RelaysArc Flash Protective Relay SystemsObjective:

•To detect arc flash event and trip upstream breaker•Pros:•Detection Speed less than 2ms•Integration into LV and MV equipment•Cons:•Coordination may be required with other protective devices•May have inappropriate operation •Must have fault interruption device that acts less than ½ cycle(~8ms) to prevent significant damage

Additional considerations!

•Speed determined by relay and breaker operation (MV AND LV)

•Can reduce PPE level for personnel

• Arc flash study required.

•Equipment damaged recovery time dependant on fault magnitude

•No true isolation of fault

•Cost is small

Passive Arc ResistantObjective:•Protect operating personnel from arc flash event by redirecting the fault energy.•Pros:•Re-enforced structure to 50kA fault current•Directs arc blast up and away from personnel•Provides personnel protection within arc flash zone•Cons:•Proper PPE required when doors are opened.•Does not isolate the fault only redirects it

Additional considerations!

•Not dependant on relay protection

•Does not reduce PPE level for personnel working in on above or below live equipment

•Equipment damaged recovery time ~16 weeks

•Access for maintenance

•Good isolation from arc flash when all access points are closed.

•Cost about 15-20 percent more than non-arc structures

•Requires consideration of plenum use.

ACTIVE ARC RESISTANT SYSTEMSObjective:•Extinguishes arc before it creates equipment damage by transforming arc energy into another form.•Pros:•Lower PPE utilization while system is active•Protects equipment•Fast recovery after event•Operating time can be less that 4ms.•Cons:•May require coordination with utility for fully coordinated system

Additional considerations!

•Can meet IEEE C37.20.7 Type 2BC

•Not dependant on standard relay protection

•Minor equipment damage with recovery time less than one day

•Excellent protection from arc flash hazard

•Cost about 15 percent more than non-arc structures.

•Zero PPE (Arc Flash Study Required)Advanced Protection

Remote Racking DeviceObjective:•To move personnel outside the arc flash zone during racking of breaker•Pros:•Allows withdrawing breaker from a safe distance•Cons:•May require personnel to mount the motor operator

Additional considerations!

Not dependant on relay protection

•Can reduce PPE level for personnel by moving outside the arc flash zone

•Good isolation from arc flash

•Cost effective

Other Devices: TIME DELAY BREAKER SWITCH

TIME DELAY CLOSE AND OPEN

Objective:•Allow Operator to move out of arc flash zone while breaker is opening or closing•Pros:•Fits into existing breaker switch mounts•No special wiring or relaying•Programmable time delay•Cons:•May not be suitable for all applications

Additional considerations!

•Does not interfere with protective relay settings

•Equipment damaged recovery time dependant on fault magnitude

•No true isolation of fault

Other Devices:CHICKEN SWITCH

Objective:•Allow Operator to move to a safe area while opening breaker•Pros:•Portable•No special wiring or relaying•Cons:•May not be suitable for all applications•May require donning some level of PPE to install•Need spare batteries for backup

Additional considerations!

•Does not interfere with protective relay settings

•Equipment damaged recovery time dependant on fault magnitude

•No true isolation of fault

•Cost can be around $4k

•Equipment must be designed for using the switch

Summary

The best system may be driven by one or more of the following• To clear faults quickly• Personnel protection desired• Lower PPE requirements• Best function for overall system integration• Recovery time after event• Cost of system• Installation requirements• Arc flash study

The most sought after goal in the workplace- Enhanced Arc Flash Protection

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You must understand and manage your Arc Flash incident

risks

Analyse, Maintain, Mitigate.

Next StepsInformation Seminars

Understand CSA Z462 and the Canadian Electrical Code

Arc Flash Analysis Determine incident energy levels and boundary distances (requires up-to-date

single line and electrical distribution data) Personal protective equipment and labeling requirements

Arc Flash Mitigation Changes to equipment protection settings Possible retrofit options to reduce arc flash incident energy levels Zone Selective Interlock, Infrared windows, high speed arc flash detection etc.

Employee Workplace Electrical Safety Programs & Training Alliance with the CSA learning centre to provide an electrical safety course

focused on arc flash hazards and proper PPE use Develop a comprehensive electrical safety program, conduct site safety audit

Design For Safety Wide variety of equipment available to mitigate arc flash hazards and protect

personnel and equipment from arc flash hazards

Facility Maintenance

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Questions?