Abstract—Since 1982 when Ralph Lee provided what many

consider the first research available on arc flash hazards in his landmark paper, The Other Electrical Hazard: Electric Arc Blast Burns, there has been growing concern about arc flash hazards in and around electrical systems. Serious study following the publication of Lee’s paper further quantified the hazard and provided a basis for calculating specific risks in specific systems. IEEE Standard 1584 was one result of this research. Additional standards, regulations, and published papers have followed making most electrical workers aware of the hazard. But, today the different standards and regulations have also caused confusion. What standard or regulation applies when and to whom? Why do different analyses provide such wide-ranging results? And once you know the hazard you face, what options do you have?

Index Terms—Arc Flash, Arc Flash Hazard Mitigation, PPE (Personal Protective Equipment), Relays, Standards.

I. NOMENCLATURE

Clearing Time (or Fault Clearing Time): The duration from fault inception to fault extinguishment. Commercial Electrical System: An electrical system operated for the purpose of powering commercial facilities, such as an office building. Commercial Sector: Relating to Commercial Electrical Systems. Industrial Electrical System: An electrical system operated for the purpose of powering an industrial plant, such as an oil refinery. Industrial Sector: Relating to Industrial Electrical Systems. Utility Electrical System An electrical system operated by a power utility, public or private, to provide electrical service to its customers. Utility Sector: Relating to Utility Electrical Systems.

II. INTRODUCTION

“Almost everyone is aware that electrical shock can be hazardous to life, although the minor shocks that many have experienced with no dire consequences tend to make them ignore this fact. There is another hazard which few appreciate—the case where contact is not necessary to incur injury. This is the radiation burn from the fierce fire of electrical arcs, due to a short circuit that develops from poor electrical contact or failure of insulation. Next to the laser, the electric arc between metals is the hottest thing on earth, or about four times as hot as the sun’s surface.”

With these words in 1982, Ralph Lee changed our view of electrical hazards in the workplace. His seminal paper brought attention to arc flash hazards for the first time. Since then extensive research has taken place to help us understand this hazard much better. We now acknowledge “the majority of hospital admissions due to electrical accidents are from arc-flash burns, not from shocks.”

It is not the intent of this paper to provide in-depth arc flash analysis review. That has been done in a number of other papers in the past few years. In addition, it is not the intent of this paper to provide great detail on the mitigation options included. Those too are collectively discussed elsewhere. Instead, this paper will: Provide a historical perspective to how we got to where we are today. Address the different standards and regulations to be considered with special emphasis on what applies when and to whom. Discuss the mitigation options available to the protection engineer. And then conclude with a couple simple application examples.

III. HISTORY

Once Ralph Lee’s paper was published in 1982, operators of industrial and commercial electrical systems seemed to acknowledge this real hazard before those operating utility electrical systems. The authors would suggest this is partly due to the third-party scrutiny (e.g., local electrical inspectors) they experience, whereas utilities are often exempt, and partly a result that their electrical systems are typically not their primary focus so they maintain a greater appreciation for electrical hazards in general. In recognizing arc flash hazards earlier, engineers designing and maintaining these electrical systems worked to better understand the nature of the hazard.

In Staged Tests Increase Awareness of Arc Flash Hazards in Electrical Equipment the authors state: “The cause and prevention of electrical arcs have been explored since the early 1960’s.” A reference review does show a number of papers written before 1982 on the subject of arc flash, but it appears most of the focus was protecting equipment. By the mid-nineties the focus had become protecting people.

Anecdotally, one author worked in the Oil and Gas business early in his career. He attended the IEEE Petroleum and Chemical Industry Conference in 1990. The Wednesday electrical safety general session that year had no mention of arc flash hazards in any of the three papers presented. He did not attend this conference again until 1995. The Wednesday electrical safety general session that year and the next three years (the last conference he attended before leaving that industry) each included papers addressing some aspect of arc

Arc Flash Hazard Regulation and Mitigation

Jay Sperl, ABB Inc., Clint Whitney, City of Richland, Andrew Milner, Iberdrola Renewables

417978-1-4244-4183-9/09/$25.00 ©2009 IEEE

flash hazards. He had been in the business for seven years at that point—working on industrial electrical systems—and remembers suddenly becoming aware of this new hazard, and realizing how often he had been exposed to the hazard without proper understanding or protection.

With all the work that took place in the mid-nineties, it still seems those responsible for utility electrical systems (for which most reading this are assumed to be included or associated) were slow to recognize this hazard. Today it seems everywhere we look in our business there is a reminder of the issue. Arc Flash standards. Arc Flash regulation. Arc Flash analysis. Arc Flash analysis software. Arc Flash consultants. Arc Flash PPE (Personal Protective Equipment). Arc Flash relays and relay schemes. Why? What has changed?

First, for the same reasons those in the industrial and commercial sector of our business were quicker to recognize the hazard, those in the utility sector were not. Less third-party scrutiny. A precedence of exemption from national standards and regulations. And a greater comfort level given electrical systems were their main focus. But in time the utility environment changed.

A number of factors contributed to this change and the increased emphasis we know today.

A. Increased electrification, more exposure

Consumers, both small and large continue to increase use of electricity. For individuals, it is driven by larger homes—most with air conditioning and modern electronics. For large energy consumers, industrial and commercial, there has been a continuous trend towards electrification for decades. As just one example, only twenty years ago, it was a common practice in industrial plants to have steam turbines as back up for electrical motors. Today, two redundant electrical motors is much more common. All said, the increased electrification requires utilities to extend their systems and this extension brings more exposure to more people.

B. Less forgiving production needs, more hot work

With a greater reliance on electricity, no alternatively-powered backups in place, and continued pursuit of greater productivity; electrical system operators are much less able to plan outages. Simply put there is less reserve in our production systems. This encourages more work be done while equipment remains energized. This increases risk for arc flash incidents.

C. General concern about hazards in the workplace

Safety in the workplace is now of the utmost concern for most businesses. This concern is underscored by our overly litigious society where the risk of being sued has never been greater. Accidents no longer happen. Someone is always at fault, even when nothing nefarious has taken place and all applicable rules have been followed. Given the concerns of litigation, and a general trend towards avoiding risk—including bad press—at all costs, companies are willing to spend more money and effort to understand and mitigate workplace risks.

D. Manufacturers started producing arc-resistant switchgear

As a result of the better understanding that resulted from arc flash research, manufacturers started looking at options to mitigate arc flash hazards. As with any new effort, it took time to move from concern to design to prototype to production to adoption. Those in the industrial and commercial sectors were first adopters. With new products now available, utility engineers had options they never had before. Justification for the new products, at a cost premium, required acknowledgement of an existing problem.

E. Ease of video sharing

The authors would also opine that video sharing has increased our awareness. Who has not seen an arc flash incident via an emailed video? This creates a new awareness of the hazard that the printed word cannot.

F. Standards and Regulations catching up with knowledge

Finally, the standards and regulations process takes time. The developers of standards and regulations are those in the business, so until they are convinced of a problem, the problem is not going to get included in standards and regulations. Once there is agreement on new provisions, the update cycle for a standard or regulation can be as long as 5 years.

IV. STANDARDS AND REGULATIONS

A. IEEE 1584

IEEE 1584 is the Guide to Performing Arc Flash Calculations. This standard resulted from the research that took place, primarily in the industrial sector, during the 1990s. The standard established a nine-step process for calculating arc flash hazards:

1. Collect electrical system data. 2. Determine modes of operation. 3. Determine bolted fault currents. 4. Determine arc fault currents. 5. Determine protective device characteristics and

durations of arcs. 6. Document voltages and equipment classes. 7. Establish working distances. 8. Determine incident energies. 9. Determine Flash Protection Boundary. However, the standard’s scope is limited to voltages from

208V to 15kV, and it provides different calculations depending on your hazard characteristics (e.g., arc in a box or arc in open air). Understanding the electrical system and using the correct basis for any calculation is critical for addressing the hazard appropriately.

B. NFPA 70E

NFPA 70E is the Standard for Electrical Safety in the Workplace. The latest version is 2009. In the previous version, 2004, this standard adopted the IEEE 1584-2002 methods for determining incident energy. It is used to determine the

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appropriate PPE based on the calculated incident energy. Section 110.8 (B)(1)(b) requires an arc flash hazard analysis

to “determine the Arc Flash Protection Boundary and the personal protective equipment that people within the Arc Flash Protection Boundary shall use.” The standard also allows use of Table 130.7(C)(9) to determine PPE requirements instead of completing a detailed flash hazard analysis. This table provides risk categories for different tasks at different voltage levels.

But the scope of this standard is limited and the standard often misapplied.

“(A) Covered. This standard addresses those electrical safety requirements for employee workplaces that are necessary for the practical safeguarding of employees during activities such as the installation, operation, maintenance, and demolition of electric conductors, electric equipment, signaling and communications conductors and equipment, and raceways for the following:

(1) Public and private premises, including buildings, structures, mobile homes, recreational vehicles, and floating buildings

(2) Yards, lots, parking lots, carnivals, and industrial substations

(3) Installations of conductors and equipment that connect to the supply of electricity

(4) Installations used by the electric utility, such as office buildings, warehouses, garages, machine shops, and recreational buildings, that are not an integral part of a generating plant, substation, or control center [emphasis added]” So, a utility’s electrical facilities of most concern with

regard to arc flash hazards—generating plants, substations, and control centers—are expressly excluded from the scope of this standard. The scope is specific for industrial and commercial facilities, and arc flash analysis references to this standard with regard to utility practices are in error.

That said, the standard includes a number of useful annexes—noted as not part of the standard’s requirements, but included for informational purposes only. Annexes C, D, H, K, and M, in particular, are good sources of information and help with regard to arc flash hazard considerations.

C. NESC

NESC is the National Electric Safety Code. “The NESC covers utility facilities and functions up to the service point.” The 2007 version includes a January 1, 2009 deadline requiring utilities to assess their system’s arc flash hazard potential and protect their employees as appropriate.

However, individual states may adopt only parts of the NESC, may delay adoption of the newest edition, and may have exemptions for certain types of utilities. For example, the state of WA only adopts parts 1-3 of the NESC (the January 1, 2009 deadline is in part 4), does not automatically adopt the newest edition and as of October 2007 still recognized the 2002 version rather than the newest 2007 version, and leaves 60 publically-owned utilities to be governed by their own

boards or committees. Recently the IEEE undertook a survey of all Public Service

Commissions (or similar state regulatory bodies) to understand the adoption of the NESC by state. The results can be found at: http://grouper.ieee.org/groups/nesc/PUCsurvey2007.pdf.

In addition to differences by state, there are exceptions to NESC Rule 410A3:

• “If the clothing required by this rule has the potential to create additional and greater hazards than the possible exposure to heat energy of the electric arc, then clothing with an arc rating or arc thermal performance value (ATPV) less than that required by the rule can be worn.”

• “For secondary systems below 1000 V, applicable work rules required by this part and engineering controls shall be utilized to limit exposure. In lieu of performing an arc hazard analysis, clothing or a clothing system with a minimum effective arc rating of 4 cal/cm2 shall be required to limit the likelihood of ignition.”

Tables 410-1 and 410-2 provide the PPE requirement based on maximum fault clearing time at different voltage and current levels.

In short, not all utilities have a January 1, 2009 arc flash mandate. Instead, each utility must judge if the NESC’s deadline applies to them. Once that is understood, each utility must then decide if any exemptions apply and what actions are ultimately required.

D. NEC

NEC is the National Electric Code. Its focus is electrical design, construction, installation, and inspection.

Section 110.16 reads: "Flash Protection. Electrical equipment such as

switchboards, panelboards, industrial control panels, meter socket enclosures, and motor control centers in other than dwelling occupancies, which 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. [emphasis added] The marking shall be located so as to be clearly visible to qualified persons before examination, adjustment, servicing, or maintenance of the equipment." This labeling requirement applies to all electrical equipment installed or modified after 2002.

E. OSHA

OSHA (Occupational Health and Safety Administration) enforces workplace safety regulations in the United States. With respect to arc flash hazards at utilities, OSHA 29 CFR 1910.269 and 1910 Subpart S apply. Subpart S (1910.333) states that “Safety related work practices shall be employed to prevent electric shock or other injuries resulting from either direct or indirect [emphasis added] electrical contacts…” However, OSHA does not provide information on how to perform work safely, just requires that it be done.

OSHA 1910.269 Appendix F Table 7 provides five “Methods of Calculating Incident Heat Energy From an

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Electric Arc”: 1. Standard for Electrical Safety Requirements for

Employee Workplaces, NFPA 70E-2004, Annex D, ``Sample Calculation of Flash Protection Boundary.''

2. Doughty, T.E., Neal, T.E., and Floyd II, H.L., ``Predicting Incident Energy to Better Manage the Electric Arc Hazard on 600 V Power Distribution Systems,'' Record of Conference Papers IEEE IAS 45th Annual Petroleum and Chemical Industry Conference, September 28-30, 1998.

3. Guide for Performing Arc Flash Hazard Calculations, IEEE 1584-2002.

4. Heat Flux Calculator, a free software program created by Alan Privette (widely available on the Internet).

5. ARCPRO, a commercially available software program developed by Kinectrics, Toronto, ON, CA.

The different options can be confusing since they provide inconsistent results. In addition there does not seem to be a limit to how you use the different calculation methods. That is, you can use different methods throughout your analysis to manipulate the results.

When considering OSHA, particular note should be made of OSHA’s General Duty Clause. This clause—Section 5 of the Occupational Safety and Health Act—states:

“(a) Each employer– (1) shall furnish to each of his employees employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to his employees; (2) shall comply with occupational safety and health standards promulgated under this Act.”

Because the broad application of the General Duty Clause, there is a general view by electrical system operators, even while acknowledging that the different standards provide exemptions for different electrical systems, that OSHA will enforce “what they want to” independent of application of other standards or regulations. In other words electrical system operators may have exemptions that apply to their situation, but decide to implement a mitigation strategy just to avoid OSHA General Duty Clause risk.

F. Conflicts and Conclusions

1. IEEE 1584 provides guidelines for performing arc flash calculations, but proper analysis is dependent on understanding the electrical system and understanding the bases of calculations. As an example, Annex D in NFPA 70E shows different incident energy calculations based on Arc in Open Air or Arc in a Cubic Box scenarios. Other factors that will impact methodology choice are: Voltage level, indoor or outdoor installations, and above or below ground power lines. Also, it is best to use actual system information, rather than conservative assumptions.

2. NFPA 70E applies to industrial and commercial electrical systems, not utility electrical systems.

3. NESC applies to utility electrical systems.

4. Adoption of NESC will depend on location and governance of utility.

5. OSHA allows five different methods for calculating incident heat energy, but the different methods can produce wide-ranging results. This creates confusion for system operators.

6. Concern brought on by OSHA’s General Duty Clause often encourages mitigation action when applicable standards would not.

V. MITIGATION

The aim of any mitigation plan is to reduce the incident energy and thus reduce the arc flash hazard and minimize any onerous work process requirements, such as PPE level. Reviewing the calculations established by IEEE 1584, it becomes obvious that there are two inverse factors that are the basis for any mitigation plan (see Figure 1): Increase the working distance (moving outside the Flash Boundary) and decrease the fault clearing time.

E is the incident energy (cal/cm2) Cf is a calculation factor (1.0 for voltages above 1 kV, 1.5 for

voltages at or below 1 kV) En is the energy normalized for a specific time and distance

dependent on the available fault current and physical equipment (cal/cm2)

t is time (s) x is a distance factor (exponent lookup from Table D.7.2 in

NFPA 70E) D is the distance (mm) from the possible arc point to the person

Fig. 1. Example Equation

However, there is another system design option to consider

first: Reducing the magnitude of the fault current.

A. Reduce the Fault Current

Typically one can assume incident energy is proportional to the available fault current, so reducing it will provide some relief if an arc flash hazard analysis results in high incident energy numbers. The options to reduce this current are:

• Deploy electronic current limiters (reducing fault current and decreasing clearing time).

• Install current-limiting fuses. • Reduce transformer sizes. • Increase transformer impedance. • Implement impedance grounded systems. • Install current-limiting reactors. That said, these options may not be available for the

electrical system operator due to other system constraints. In addition, a reduction in fault current can potentially also increase incident energy if the reduction produces a longer clearing time for the overcurrent device. This result will

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depend on the relay scheme utilized, but makes it clear system changes require a recheck of prior analysis to confirm desired results.

B. Increase the Working Distance

Working distance is the distance from the possible arc point to the head and body of the worker positioned in place to perform the assigned task. Increasing this distance moves the worker farther from harm’s way. There are a number of ways to increase the working distance, directly and indirectly.

1) De-energizing Equipment

De-energizing equipment always provides the safest work situation for the electrical worker. This option moves the possible arc point behind the interrupting device. However, de-energizing equipment is often not an option in today’s tight production workplace; and—since restarting an industrial process is often fraught with risk—it can just shift risk to other workers in a facility, such as process operators.

2) Use technology to work away from energized equipment

Mechanical and electronic options exist to allow workers to complete their work farther from the arc point. The most common is remote racking breakers using an umbilical-cable-connected control box. Infrared inspection and video surveillance might also be included here.

3) Install warning labels (consider painting floor)

Once an arc flash hazard analysis is completed, equipment must be labeled with warnings reflecting the results. The authors have observed, however, that these labels are often fixed to the equipment and require incursion into unsafe areas just to read the warning. A related option, that is easier to follow and enforce, is to paint the floor in front of equipment in different colors reflecting the PPE required.

4) Ensure PPE Appropriate for the Hazard Level

Whether by calculation or use of a table, once an arc flash hazard analysis is completed, workers must wear PPE appropriate to the analysis results.

C. Decrease the Fault Clearing Time

Fault clearing time is the duration from fault inception to fault extinguishment. Decreasing the fault clearing time will decrease the incident energy and minimize the damage to people or equipment. There are different options, either alone or combined, to decrease fault clearing time.

1) Increase fault current

As noted above, there can be a counterintuitive incident energy calculation response due to the overcurrent protective device’s reaction to the fault current. In some cases it may make sense to actually increase the fault current to lower the incident energy.

2) Install faster (3-cycle or 5-cycle) breakers

Protection engineers might design a relay scheme that is quite fast, but if that relay scheme sends a trip signal to a slow

circuit breaker (e.g., a 12-cycle breaker), the benefits of the fast relay scheme are undermined. New breakers should have a 3- or 5-cycle rating. With such breakers a fault clearing time of less than 100ms (6 cycles) is possible. And once installed, breakers must be maintained in good operating condition to continue to operate within design parameters.

3) Consider or reconsider relay scheme

a) Recheck coordination focused on arc flash mitigation

Once an arc flash analysis is completed, it is often valuable to recheck the relay coordination study specific for arc flash mitigation. Relay engineers are typically conservative. This is exhibited two ways: 1) The use of bolted fault currents as a basis for coordination studies and 2) The typical use of 0.3-second coordination interval between the inverse time current curves of overcurrent devices. These are good practices, but may exacerbate the arc flash characteristics of a system.

Using an arcing fault current basis and setting overcurrent devices accordingly can provide a more realistic picture of the fault clearing time.

In addition, with arc flash mitigation in mind, the security provided by the 0.3-second coordination interval may not be as important as ensuring the fastest fault clearing time possible.

The advantage of this recheck is it requires no new equipment. The disadvantages are the cost of the coordination study recheck, the potential insecurity reduced coordination intervals may create (although newer technologies, such as IEC61850, may make it possible to reduce coordination intervals more than possible in the past), and the trip times are still relatively slow.

b) Zone interlocking

A zone interlocking scheme uses blocking signals to respond differently depending on the location (or zone) of the fault. As such, this provides an ability to supervise fault response and provide a faster tripping option for zones where an arc flash is more likely or where personnel are more likely to work.

The advantage of this scheme is it can use existing equipment and is typically faster than simpler time overcurrent schemes. The disadvantages are the cost of a new coordination study and additional complexity.

c) Bus differential

A bus differential scheme is based on Kirchoff’s Current Law. During normal operation the sum of all currents entering and exiting a node must add to zero. However during an abnormal event within the protected node, or zone of protection, this sum is not zero and the node is isolated to clear the fault.

This scheme, whether a high-impedance or low-impedance type, is fast and secure but can be relatively costly because it can require dedicated CTs, complex settings, additional wiring, and extra testing.

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d) Enable instantaneous overcurrent protection during maintenance

Perhaps the most popularly discussed relay scheme for arc flash hazard mitigation is to use instantaneous protection during maintenance activities. In this option the maintenance workers use a switch or pushbutton to enable instantaneous overcurrent protection while working in the area. There has also been some discussion of an automatic switchover option whereby a motion detector could be used to invoke a change in relay settings (e.g., enabling an alternate settings group).

The advantages of this scheme are that the critical equipment should already be in place, and only simple changes (adding a control switch or pushbutton, adding some control wiring, and updating the relay settings slightly) are required to implement the scheme. The disadvantage of this scheme is it depends on actions by maintenance workers that may become casual with the procedures over time. There is also the small risk—becoming a large risk if normal settings are not restored at the conclusion of the maintenance activities—of overtripping during these maintenance activities, a trade-off for the increased safety.

e) Optical sensors

Since arc flash faults emit such a high intensity light, one option that is growing in popularity is the use of optical sensors. These schemes typically use fiber optics—either a non-jacketed sensor fiber that detects light along its entire length or a lens fiber that detects light only at its terminal end—to detect the arc flash.

To ensure security of detection, optical sensor relays also have a current input to supervise the light detection. As such, the trip signal is only sent to the connected breakers when an overcurrent condition also exists when the arc flash is detected.

The advantages of an optical scheme are: Speed (2.5 ms trip signal). Its independence from other relay schemes—it does not need to be coordinated with other deployed schemes. Its trip time is independent from fault current magnitude. And finally, it is not dependent on work procedures. That is, it operates whether the worker remembers to follow all the required work procedure steps or not. The disadvantages of this scheme are the inconvenience and cost to retrofit on existing switchgear installations and it does not provide any help in outdoor, open air systems. However, such outdoor systems generally have lower incident energies than switchgear installations.

VI. APPLICATION EXAMPLE 1 (CITY OF RICHLAND).

A. Arc flash hazard assessment conclusion

8 cal/cm2 PPE provides sufficient mitigation.

B. Overview

Application Example 1 involves a typical distribution substation transformer and metalclad switchgear. (The One-line diagram is shown in Figure 2.) The utility’s work and exposure is typically on the low side of the transformer. As such, the discussion and review will focus on that aspect. For simplicity in this example, the comparison and calculations will exclude arc in a box situations.

C. Design Assumptions

For reference, the 15MVA substation power transformer high side is 115kV grounded wye with a 12.47kV grounded wye secondary and an impedance of 7.8%.

Given and assumed parameters: • 9kA maximum fault calculated from transformer

impedance only. • 24” distance between employee and fault based upon

minimum approach distance (2’2” per NESC Table 441-1).

• Boundary energy of 2 cal/cm2 as cotton clothing won’t provide enough protection over that value (OSHA 1910.269 Appendix F(II)(A)).

D. Mitigation

This information, as well as the clearing times from the time coordination curves, was input into the IEEE 1584 spreadsheet (see Figure 3) with the results shown in Figures 4 and 5.

The results indicate the load side of the feeder breakers may experience an arc flash incident energy of 2.0 cal/cm2. Between the feeder breakers and the circuit switcher, the arc flash incident energy may be 7.9 cal/cm2.

Since most utility work will be on the distribution system protected by the feeder breakers, 4 cal/cm2 clothing will be used. Additional protection will be necessary for protection against arc in the box situations. Most FR (Flame-Resistant) clothing manufacturers provide 8 cal/cm2 clothing—shirts and pants—that appear very similar to everyday-wear clothing. This facilitates adoption by employees. An informal check confirmed other utilities have similar plans to use 8 cal/cm2 clothing.

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Fig. 2. Application Example 1 One-line

Fig. 3. Arc Flash Input Parameters

Fig. 4. Arc Flash Calculations

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Fig. 5. Arc Flash Summary

VII. APPLICATION EXAMPLE 2 (IBERDROLA RENEWABLES).

A. Arc flash hazard assessment conclusion

Divergent concerns require a belt and suspenders approach including a dedicated optical sensor relay scheme.

B. Overview

Application Example 2 is a typical large-scale wind project collector substation. The switchgear is metalclad with eight to ten 34.5kV breakers. (The typical one-line diagram—showing a single 34.5 kV breaker—is shown in Figure 6.)

C. Design considerations and challenges

Arc flash safety must be ensured for Operations and Maintenance personnel who are specialized in the maintenance of wind turbine generators and have little experience with substation equipment. Further, since collector substations are often shared with utilities and other developers, the arc flash mitigation measures must also ensure safety of personnel not employed or trained by Iberdrola Renewables. Finally, down time must be minimized.

D. Mitigation

In a belt and suspenders approach, overlapping arc flash mitigation options will be implemented:

• The arc flash hazard area (area in front of the switchgear) is closed off by a chain-link gate. Signage is installed on the gate clearly describing the safety hazards and required PPE needed within the arc flash hazard area.

• A mimic panel is used so that all controls of the switchgear breakers and relays can be operated well away from arc flash hazard area.

• Breakers can be racked out through a remote device so personnel do not have to stand within the hazard area to perform this operation.

• An optical sensor arc protection system is deployed throughout all breaker cubicles within the switchgear building. This limits the energy and duration of the blast, thus decreasing the hazard to personnel and limiting damage to equipment.

Fig. 6. Application Example 2 One-line

VIII. CONCLUSIONS

• Arc flash hazards cause more injuries than shock hazards.

• The utility electrical system environment has changed.

• Standards and Regulations provide guidelines, requirements, and inconsistencies. Exemptions perceived as tenuous.

• There are many mitigation options. Each has advantages and disadvantages.

• No cookie cutter approach to mitigation. Each utility will be somewhat unique in approach.

REFERENCES

[1] R. H. Lee, “The Other Electrical Hazard: Electric Arc Blast Burns,” IEEE Trans. Ind. Appl., vol. 18, no. 3, pp. 246-251, May/Jun 1982.

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[2] R. A. Jones, et al., “Staged Tests Increase Awareness of Arc Flash Hazards in Electrical Equipment,” IEEE Trans. Ind. Appl., vol. 36, no. 2, pp. 659-667, Mar/Apr 2000.

[3] C. Inshaw and R. Wilson, “Arc Flash Hazard Analysis and Mitigation,” presented at Western Protective Relay Conference, Spokane, WA, October 20th, 2004.

[4] Guide to Performing Arc Flash Calculations, IEEE Standard 1584, 2002.

[5] Standard for Electrical Safety in the Workplace, NFPA Standard 70E, 2009.

[6] NESC (National Electric Safety Code), ANSI/IEEE Standard C2, 2007.

[7] IEEE Standards Association, [Online] Available: http://standards.ieee.org/faqs/NESCFAQ.html#q7

[8] NEC (National Electric Code), NFPA Standard 70, 2008. [9] Occupational Safety and Health Act of 1970, Public Law 91-596, 84

STAT. 1590, 91st Congress, S.2193, December 29, 1970, as amended through January 1, 2004.

[10] J. Kumm, “Five Ways to Reduce Arc Flash Hazards”, System Protection Services Newsletter, [Online] Available: http://www.systemprotection.com/Literature/newsletter_archive/

[11] J. Buff and K. Zimmerman, “Reducing Arc Flash Hazards: Applying Existing Technologies.” IEEE Ind. Appl. Mag., May/Jun 2008.

[12] K. Zimmerman, et al., “Protection Considerations to Mitigate Arc Flash Hazards” IEEE PSRC WG K9, Draft Technical Report, unpublished.

Jay Sperl is a Regional Technical Manager for ABB Inc. in Prosser, WA. He received his BSEE degree Washington State University in 1988. He is a Member of IEEE and a Registered Professional Engineer in California. Clint Whitney is the Electrical Systems Supervisor for the City of Richland in Richland, WA. He received his BSEE degree from Washington State University in 1991. He is a Senior Member of IEEE and a Registered Professional Engineer in Washington. Andrew Milner is an Electrical Engineer in Wind Technical Services for Iberdrola Renewables in Portland, OR. He received his BSEE degree from Oregon State University in 2003. He is a Member of IEEE and a Registered Professional Engineer in Oregon.

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