ARC FLASH HAZARDS IN THE WORKPLACEPresented at the 2006 Annual GEAPS Convention

Gregory DiFrank P.E.Vice President – General Manager, Columbus Office

Joseph Bracone E.I.T.Electrical Engineer

River Consulting, Columbus, Ohio

Introduction

Electrical arc flashes aren't new, but new research is beginning to show just how dangerous and damaging they can be. This paper will discuss just what arc flashes are, and then begin to lay out what steps can be taken to limit and avoid the personal injury and company damages they cause. It will cover codes and compliance issues, show how facilities can assess the hazards of arc flashes in their plant's electrical systems, and then provide solid information about the ways to implement an arc-flash safety system.

What is an Arc Flash?

The NFPA defines an Arc Flash as “a dangerous condition associated with the release of energy caused by an electric arc.” In order to better define an Arc Flash, and to allow a better understanding of the causes and reasons behind one, one other definition must be established. This definition is as follows:

Arcing Fault – The flow of electric current through the air between buses, conductors, or any other pieces of an enclosure at separate voltage levels. Faults are typically restricted to voltage differentials of over 120 volts, as it is extremely difficult to maintain an arc at lower voltages. This arc fault will release an incredible level of energy in a near instantaneous amount of time. This energy release results in an extremely high temperature and vaporizes any copper within the equipment, causing an explosive volumetric increase, in a ratio range of anywhere between 40,000 to 67,000 to 1. This expansion causes a detonation within the piece electrical equipment, and the remains of the electrical equipment may be thrown at high speeds, sometimes in the excess of 700 miles per hour.

The amount of electric current flowing through the arc is usually much less than the available fault current at the panel location. This can often be well below normal protective device ratings. In these conditions, the fault condition can occur without being immediately interrupted by the overcurrent protective device (circuit breaker, fuse).

Once an Arcing Fault has been defined, an Arc Flash can be defined as the rapid release of energy due to such an arcing fault, causing damage to personnel, electrical equipment, and the facility.

An electrical arc occurs when there is a flow of energy between two electrically charged objects where there is no path for the current to follow other than air or insulated material. Two major causes of arcs are insulation failure and human error. Heat, humidity, and aging can cause the insulation on wiring to become brittle and crack. Build up of dust and other contaminants along insulators can result in small arcs that permanently damage the insulation between conductive surfaces within a piece of electrical equipment, allowing arcs to occur with more frequency and larger magnitude. Other minor causes of arcs include small animals and insects, who after crawling inside electrical equipment, can contact a conductor and create a path to ground to initiate a fault. Vibration and metal fatigue can lead to the breaking of connections and electrical leads, which can then contact the enclosure or other conductors. Human error is the overall grouping of accidental contact with exposed electrical parts. This can include dropped tools, an inadvertently placed hand, or something as simple as inserting a tool in the wrong place of a piece of electrical equipment. It can also include improper operational or troubleshooting procedure, such as walking up to a panel board and resetting a tripped breaker without first investigating the cause of the tripped circuit.

As previously mentioned, the amount of current flowing in an electrical arc is usually much less than the available bolted fault current at the panel location. This fault current is also often initially below normal protective device ratings, allowing the fault current to flow for some time before interruption. The amount of energy, and therefore damage, caused by an arc fault is proportional to the available fault current at the electrical device. The available fault current in an electrical system can be calculated using a complex method of equations. This is often done with the assistance of one of the many computer programs that exist to calculate the available fault current for a facility. There is a direct relationship between the voltage level that the equipment operates at, and the available fault current at that piece of equipment. The following table gives electrical current and energy ranges typically associated with different voltage levels.

Typical Voltage Levels

Typical Short Circuit Fault Current Levels

Typical Short Circuit Fault Three Phase Energy Levels

208/120 V 5,000 A - 40,000 A 2 MVA -15 MVA480 V 10,000 A - 100,000 A 8 MVA - 80 MVA

4,160 V 35,000 A - 70,000 A 250 MVA - 500 MVA13,800 V 20,000 A - 60,000 A 500 MVA - 1500 MVA

Table 1. Typical Current and Energy Levels Available At Different Common Voltage Levels

In general, higher voltage levels lead to higher fault energy levels, which in turn lead to greater arc flash blasts. There can be variation at a voltage level, but on the whole the greater the voltage the greater the risk. The fault current interrupting rating specified for any piece of electrical equipment should be based on the available fault current at that respective point in the electrical system where the piece equipment is located. The higher the withstand or interrupting rating of the piece of electrical equipment, the greater an arc blast damage level the equipment can withstand without being blown apart.

Concerns over Arc Flash

Five to ten arc flash blasts occur every day in the United States. Arc flashes may occur around any piece of electrical equipment, and are not selective, though for the most part, faults are typically restricted to equipment with voltage differentials of over 120 volts. The dielectric breakdown strength of dry air at typical room temperature and sea-level pressure is about 33 kV per cm. As a standard rule of thumb, for air at STP, the minimum spark-over voltage is around 380 volts. Given the concussive nature of the rapid expansion of vaporized gasses, and the resulting debris and shrapnel, the arc blasts that result from an arc flash may have the possibility of killing or injuring any personnel working in the vicinity of the equipment, not just an employee working on the respective piece of equipment.

As previously stated, an arc flash is defined as the release of energy from an electrical arc. Within those electrical arcs, the core temperatures may sometimes reach levels greater than 5,000 degrees Fahrenheit. The temperature of the surface of the sun is believed to be around 10,000 degrees. Temperatures at that level establish a plasma bridge between conductors that is highly conductive and will allow as much energy as is available in the local power distribution system to flow across the arc. Most overcurrent protective devices (circuit breakers, etc.) will not trip until this plasma bridge has already been established. Thus, by the time the protective devise has activated, the process of an arc blast has already been set in motion.

As can be imagined, the injury caused to any personnel working on or near a piece of electrical equipment by temperatures approaching 5000 degrees can be catastrophic regardless of any shrapnel thrown clear of the electrical equipment. Severe and even fatal injury can be the most horrible result of arc flash burns; however, extensive damage can be caused even when the injuries are not fatal. Lungs can be injured by the hot gasses inhaled, and breathing operations for anyone close to an arc flash can be severely impaired. True lung burn occurs only if you directly breathe in a hot source. In the case of many arc flash blasts, the high pressure blast can force the heat into the victim. Even though thermal injury is typically confined to the upper airways in these instances, because the trachea usually shields the lung from thermal loads, the damage to a normal human respiratory system can be irreparable and in some cases fatal. When hot air enters the nose, damage to the mucous membranes can readily occur as the upper airway acts as a cooling chamber.

Body burns are a typical byproduct of arc flash blasts. Burn levels are typically broken down into three categories: first, second and third-degree burns. The most severe levels of burns are third- degree burns. Third-degree burns affect all layers of the skin. Healing from third-degree burns is very slow due to all of the skin tissue and structures being destroyed, and in most cases complete healing will never occur naturally. Third-degree burns are typically so deep that only the edges of the affected area will heal and in most cases result in extensive scarring if skin grafting is not performed. Second-degree burns are less serious than third degree and only affect the outer-layer and the underlying layers of skin causing redness, pain, swelling and blisters. These burns often affect sweat glands and hair follicles. In most cases second-degree burns will heal over time though scarring will typically occur. First-degree burns are red and very sensitive to touch. First-degree burns involve minimal tissue

damage and typically involve only the outer-layer of skin causing pain, redness and swelling. Sunburn is a good example of a first-degree burn. Typically, most arc flash burns are of the third-degree, or most severe, level.

In addition to burns and personnel injuries, extensive downtime, personnel lost time, and equipment destruction are typical consequences of arc fault blasts. All facilities know the costs of downtime and repair of major equipment. Pieces of electrical equipment can cost anywhere from $2,000 for a small panelboard to well over $100,000 for larger pieces of electrical gear, and the lead time to have a new piece of electrical equipment delivered to a facility can easily range anywhere from eight to 12 weeks or more. Having portions of a facility shut down and not available for production for several months due to lack of electrical equipment is typically a staggering loss for a company.

Pictures of Arc Flash Burns

Pictures are the most explicit way to show the results of unprotected personnel who come in contact with arc flash blasts.

Figures 1-5. Pictures of burns suffered during electrical arcs as seen on OSHA’s website.

General Procedures to Reduce the Risks of Arc Faults

Reducing the risk of arc flash exposure at a specific facility can be accomplished by a number of means. The first of these include performing preventative maintenance to repair damaged or unacceptable equipment components and insulation. The easiest way to ensure that personnel are less susceptible to an arc flash is to perform all maintenance on electrical equipment with the incoming power to the equipment disconnected. With no power flowing into the equipment, no arc flash can occur. Routine shutdowns of electrical equipment for a brief period, especially on older pieces of equipment, along with cleaning and a thorough inspection can be used to determine if future problems within a particular piece of equipment are more likely to cause that piece of equipment to become more susceptible to a fault. Rack mounted breakers and other large switches can be swapped out with spares and periodically cleaned and inspected off-line. Thermographic inspections of electrical equipment can show hot spots that may indicate impending failure. Numerous electrical maintenance practices already exist that can help predict possible sources of trouble in electrical power systems and allow repairs to be performed before a fault actually occurs.

Other practices can help make a piece of equipment less susceptible to electrical faults. Maintenance programs can be initiated to ensure plant personnel use only corrosion resistant terminals, insulate or guard exposed metal parts within pieces of electrical equipment where possible, seal all open areas in the enclosure of electrical equipment to prevent birds and other small animals from entering the equipment, and finally make certain that all relays, switches, circuit breakers, and other protective devices within all pieces of electrical equipment in a facility operate properly. If a piece of equipment must remain energized either for maintenance or production reasons, some other simple practices can be used to reduce exposure to arc hazards within a facility. If the piece of equipment is unable to be sufficiently maintained or repaired in a timely fashion, personnel can be warned to be extra careful around the suspect equipment until repairs can be made.

Purpose of Arc Flash Studies

Beyond making repairs to and maintaining electrical equipment to reduce the probability of a fault, the next most effective way to help employees avoid exposure to an arc flash is by identifying the potential hazard to the employees and training them in ways to avoid the hazard. This is where the arc flash study becomes an important part of the overall facility safety program.

An early 1980s paper by Ralph Lee published in the IEEE Transactions on Industrial Applications called “The Other Electrical Hazard: Electric Arc Blast Burns” brought to attention the need to protect those working around electrical equipment from the dangers an arc blasts poses. Today, four main standards exist that compel employers to assess the hazards in their workplace, guide them in studying and quantifying those hazards, and assist in establishing practices for providing warning to employees of the dangers of arc blasts in electrical equipment. These standards encourage arc flash studies to be

performed on facilities to keep electrical workers better prepared for the dangers of arc flash blasts, including shock, electrocution, burns and explosions. The four standards include:

29 CFR (Code of Federal Regulations) Part 1910 Subpart S (OSHA) NFPA 70-2005 - National Electric Code (NEC) NFPA 70E-2004 - Standard for Electrical Safety in the Workplace. IEEE Standard 1584-2002 - Guide for Performing Arc Flash Hazard Calculations.

These standards and codes work together to form the impetus and establish the practice for addressing arc flash hazards in facilities. In general, the chain of reference is as follows:

29 CFR (Code of Federal Regulations) Part 1910 Subpart S (OSHA) – OSHA clearly requires that employers assess the hazards present in the workplace and identify and provide personal protective equipment (PPE) to be worn by employees to protect them from those hazards. It also references NFPA 2004-70E, Standard for Electrical Safety in the Workplace, as an Industry Consensus Standard that can provide information useful in understanding and complying with the requirements contained in Subpart S.

NFPA 70-2005, National Electric Code (NEC) – Article 110.16 clearly requires that all switchboards, panel boards, industrial control panels, meter socket bases, and motor control centers likely to require maintenance while energized, be field marked to warn persons of potential arc flash hazard. It also references NFPA 2004-70E, Standard for Electrical Safety in the Workplace, as a source for assistance in determining potential severity of exposure, planning safe work practices, and selecting personal protective equipment.

NFPA 70E, Standard for Electrical Safety in the Workplace – requires employers to perform a flash hazard analysis. It goes on to provide guidelines for performing the flash hazard analysis, calculating arc flash energy levels and protection boundaries, determining limits of approach, and selecting PPE. It references IEEE Standard 1584-2002 - Guide for Performing Arc Flash Hazard Calculations, for use in helping to determine arc flash energy levels.

IEEE Standard 1584-2002, Guide for Performing Arc Flash Hazard Calculations – This standard provides the technical foundation for the calculations used to determine potential flash hazard energy levels and protection boundaries.

In general, the purpose of an arc flash study is to calculate the potential flash hazard present at a specific piece of equipment. Done correctly, the study will identify the amount of energy in the potential flash. This can then be used to establish the flash protection boundaries, as well as determine the level of PPE required when servicing the equipment while energized.

NFPA 70-2002 (NEC) explicitly requires that warning labels be placed on all switchboards, panel boards, industrial control panels, meter socket enclosures, and motor control centers likely to require maintenance while energized. NEC requires only that the labels provide a warning of a shock hazard.

Industry practice however, has evolved to provide a label with much more detailed information. A typical arc flash label should include the following information:

Arc Flash Boundary Incident Energy at 18” Expressed in cal/cm2 PPE Required Voltage Shock Hazard Level Limited Shock Approach Boundary Restricted Shock Approach Boundary Prohibited Shock Approach Boundary

These values should all appear on any arc flash label installed within a facility. A typical arc flash label containing this information is shown below.

Figure 6. Typical arc flash label showing the information pertaining to the flash hazard, approach limits, and PPE requirements per NFPA 70E.

The Flash Protection or Hazard Boundary is derived from a calculation based upon available short circuit current, the fault duration given by the overcurrent protective device, and the voltage level. It provides an estimation of the distance from the surface of live parts that an arc may occur.

The Flash Hazard is the available energy of the arc at the distance given. As a reference, one calorie per square centimeter is said to be equal to the feel of holding a finger over the tip of the flame of a cigarette lighter for one second.

The PPE level is the personal protective equipment level that is recommended based upon the Flash Hazard level. Each level corresponds to a recommended type and amount of protective gear. These clothing levels are described in further detail in NFPA 70E and later in this paper.

The kV shock hazard level is the maximum voltage level present within the associated electrical enclosure.

According to NFPA 70E, Limited Approach Boundary, Restricted Approach Boundary, and Prohibited Approach Boundary are defined as the following:

The Limited Approach Boundary is a point at a distance from an exposed live part within a piece of electrical equipment at which a shock hazard exists. Any plant personnel within this radius are in danger of electrical shock or electrocution, regardless of how small a chance.

The Restricted Approach Boundary is a point from an exposed live part within a piece of electrical equipment at which there is an increased risk of shock, due to electrical arcs combined with inadvertent movement, for personnel working in close proximity to the live part. Chances of a shock hazard are much greater than the Limited Approach Boundary.

The Prohibited Approach Boundary is a an approach limit at a distance from the exposed live part within which work is considered the same as making contact with the live part. Electrical shock is very likely to occur at this distance.

Hazard levels are broken down into six categories. The lower the category, the less short circuit current present within the piece of equipment, and the less likely the associated piece of electrical equipment is to have a high power arc blast. In addition to the reduction in energy level associated with any arc faults, the approach boundaries move closer to the energized piece of equipment for a lower hazard level. The associated table shows the PPE categories along with the maximum cal/cm2 level allowed to be considered within that PPE category. An abbreviated description of the NFPA 70E clothing characteristics required to work on a piece of equipment at that associated PPE category is also listed.

Table 2. Arc flash hazard category levels, associated energy levels present, and protective clothing characteristics required for personnel maintaining electrical equipment while energized.

The above table is not all inclusive of the PPE requirements at the various category levels. Additional protection, including face and eye protection, hand protection, and foot protection, are required at all levels. NFPA 70E should be consulted for complete details of PPE requirements at the

various levels. Finally, it should be noted that while the PPE required by NFPA 70E will provide some degree of protection from the heat of an arc flash, there remains other hazards, including concussive forces and noxious vapors, that the PPE provides only limited protection against.

Energized or live work permit procedures, which are often developed as part of an arc flash study, are also an effective way to warn workers of the dangers they will face while working on a piece of live electrical equipment. Utilizing live work permits will also allow the personnel working on the live equipment to ensure that other workers will be reasonably protected by allowing all nearby workers to know that live work is being performed in an adjacent area. In addition to the previously mentioned benefits, the live work permits have a series of sign-offs to ensure that live work is being performed by qualified personnel, and that responsible people are aware of the work to let all other employees working in neighboring areas know of the live work. No one should ever be allowed to enter a work area unless they are qualified and properly protected. Never allow personnel to “look over someone else’s shoulder” while a qualified person is working on electrical equipment. Proper approach boundaries must be maintained at all times.

What an Arc Flash Study Means to a Facility

There are many reasons a facility should perform an arc flash study. In addition to the regulatory requirements expressed by OSHA and the NEC, statistics predict that the explosive energy released during an arc fault will send more than 2,000 North American workers to burn centers this year. Even though arc blasts are not as frequent as other electrical injuries such as shock, the severity involved in arc blasts makes the harm and losses of human life much greater. Dollar costs for incidents of arc blasts injuries can easily reach six figures, and this amount only covers the medical expenses and down time of the employees affected. The cost of equipment replacement, downtime, insurance rate increases, and lost production can increase the cost of one arc blast incident even more than the medical expense costs. There are many options and decisions to be determined when having an arc flash study performed upon a facility. These decisions determine the effectiveness and shelf life of the arc flash study.

Worker safety is the main concern the previously mentioned codes hope to address with the new labeling and clothing requirements given therein. By warning employees of the dangers involved within an energized electrical enclosure, and by ensuring that proper protective clothing is worn by all employees working on energized electrical equipment, code officials feel the number of serious burns and fatalities due to arc blasts can be reduced. The clothing requirements for working on different levels of hazard category are designed to prevent loss of life and reduce any burns received by personnel to a second degree level. The approach boundaries set by the NFPA 70E are effective ways to warn unprotected employees of safe distances around energized electrical equipment being worked upon. See the following detail from NFPA 70E for details on approach boundaries.

Figure 7. Layout of approach boundaries around an exposed live piece of electrical equipment.

However a facility looks at arc flash studies, most everyone can agree that codes and regulations are often less than clear, and the details of how to specifically comply with the regulations are often left up to the interpretation of the industry and individual facilities. There is a clear trend in the electrical design and construction industry to move towards complete study of electrical systems for arc flash hazards, and full compliance with NFPA 70E where labeling and development of PPE recommendations are concerned. There has also been a noticeable trend of increased knowledge of and enforcement of these requirements on the part of OSHA inspectors.

In addition to worker safety, having an arc flash study performed helps demonstrate a commitment from management to employee well-being. An arc flash study can also establish an environment conductive to safety that will filter down to other areas of a facility. All of these reasons to have an arc flash study performed are in addition to the basic overriding reason that proper warning labeling is required by NEC for all pieces of electrical equipment that will be maintained while energized.

Theoretically, an arc flash study for a facility only needs to be performed once to establish the hazards, labeling and PPE requirements. However, in reality this is never the case. Modifications to the power system in the facility, or major modifications to the utility service feeding a facility and to upstream components of the facility power system, most noticeably transformer and overcurrent protection sizing, can make additional arc flash studies necessary. A three to five year time frame between studies has been recommended by numerous sources. As a rule, any major changes to the available fault current at a piece of electrical equipment or overcurrent protection for a piece of electrical equipment will affect the arc flash rating of the equipment. Also, other considerations that should be considered on how often an arc flash study should be performed include:

A facility safety audit is being required by a code official or inspector. The facility’s safety policy is up for renewal.

Modifications or expansions of the electrical distribution system are being considered or have recently occurred.

The typical shelf life for a short circuit study is 5 years; arc flash studies are typically in the same timeframe.

Performing an Arc Flash Study

In order to perform an arc flash study for a facility, there are many pieces of information that must be known and calculated. Many engineering firms performing studies take it upon themselves to obtain this information; however, having some of this information available and ready before contacting an engineering firm can greatly reduce the time necessary to accomplish an arc flash study. The most necessary piece of information required to perform an arc flash study is an accurate electrical one-line of the facility being studied. The one-line provides data necessary to the arc flash study, including cable and transformer sizing and overall power system layout.

A thorough arc flash study also needs the overcurrent protective device settings of all protective devices (circuit breakers, fuses, protective relays) located within the facility. The settings of these devices give the predicted fault duration, which will be used to determine the arc clearing time that in turn determines the incident energy and approach boundaries radii. The settings of the overcurrent protective devices are typically obtained by the personnel performing the arc flash study, which is a good opportunity to verify the information on the facility one line drawings. During the site investigation, the arc flash personnel must determine which electrical enclosures and panels require arc flash labels, as typically, only panels with voltages over 120 volts have arc flash instances and requirements.

Once the field data has been collected, a short circuit study can be performed. A short circuit study is the basis for any effective arc flash study. When performing a short circuit study, one of the main pieces of information that must be determined is the utility contribution to any faults. There are two methods to determine the utility contribution to a short circuit study, and in turn its contribution to an arc flash blast. All utility companies can give a facility it services the utility short circuit current available at its service entrance point. By using the utility company’s information, a facility will get a more accurate portrait of its arc flash levels, and in general lower calculated arc flash hazard levels will be the result.

However, performing an arc flash study using the given utility information makes the study more apt to inaccuracy over longer periods of time. If the utility upgrades its substation or transmission lines, or even adds or removes customers, the amount of available short circuit current at the service entrance of the facility could increase, resulting in incident energy greater than the amount listed on the labels attached during the original arc flash study. The facility has very little to no control over these utility upgrades, and thus will be at the mercy of the utility company as to how and when additional arc flash studies need to be performed.

On the other hand, if the personnel performing the arc flash study assume an infinite utility contribution at the point of service, a facility is no longer dependent on the utility as to how often it

needs to re-perform an arc flash study. No matter what the utility changes or when it is changed, the utility contribution cannot exceed the infinite level assumed in the arc flash study. One drawback to assuming an infinite utility contribution is that it represents a more conservative approach that in some cases could result in a higher hazard level being calculated for a panel than the hazard level that is actually present within that same panel. This will lead to a higher PPE requirement for personnel servicing the panel than may be necessary. Each facility will have to decide on how it wishes to weigh these trade-offs based on its experience and vigilance in monitoring the condition of its power system and the use of PPE by its employees.

Performing an arc flash study is a complex endeavor that requires education, training, and experience with power distribution system design. It should only be performed by professionals with bachelor level degrees or equivalent education, and under the supervision of registered professional engineers. It usually requires a type of computer software to perform effectively. There are a few options when looking at the different software packages, and some of them include POWER*TOOLS by SKM, ETAP by OSI, and ESA’s EasyPower software. In addition to these pieces of software, many electrical engineering firms offer arc flash studies as a service to all types of facilities.

How long an arc flash study typically takes to complete depends on the size of the facility in question. The more labels that need to be created typically push the completion date of the study further. Typically, most facilities that have accurate one-lines can be walked in a matter of days with one member of the plant’s maintenance staff assisting the engineer responsible. Once the plant walk has been completed, it will typically take a number of weeks to enter the information into the computer software packages, perform the calculations, and begin the process of printing labels. Labels can typically take anywhere from a couple of days up to a week to print properly. Overall, most arc flash studies can be completed in less than a month after the responsible engineer receives the necessary information mentioned in this paper and has performed a complete walk-through of the facility being studied.

For reference, a typical inland terminal or river terminal with twenty to thirty motors could likely be field surveyed in a day, and would need approximately a week of an engineers time to perform calculations and generate labels. A large facility such as an export elevator or major mill, with several substations and hundreds of motors, may require a week or more of field survey time, and a month of office engineering to perform calculations and generate labels.

Conclusion

Though it is always preferable for employees to work on de-energized electrical equipment, this is not always possible in today’s production environments. An arc flash study is a useful and necessary tool to allow an employer to identify the hazards, select the PPE, and develop the procedures that will protect workers from arc flash blasts that occur everyday in facilities nationwide. These studies give valuable information on the dangers present within a piece of energized electrical equipment, as well as the approach boundaries that should be maintained around electrical equipment for unprotected personnel. Conducting an arc flash study is part of an overall electrical safety process that involves a number of simple steps, including:

Collecting the field data Retaining a qualified engineer to perform the calculations Printing and applying the labels Selecting and making available the appropriate PPE Developing appropriate procedures for maintenance of electrical equipment Training employees and enforcing the use of PPE and approved procedures

OSHA inspectors are now beginning to enforce NFPA 70E and the arc flash labeling requirements listed therein. Delay in performing an arc flash study and implementing the labeling and PPE requirements in NFPA 70E will put facilities at a growing distance from accepted industry practice. The cost of the engineering, labels and PPE is modest when compared to the potential for monetary loss and human injury. With virtually no interruption of operations required to implement, all facilities should consider moving forward with flash hazard analysis programs as soon as is practical.

References

1. Gregory, George (2003). Preventing Arc Flash Incidents in the Workplace. EC&M The Magazine of Electrical Design, Construction & Maintenance, 6, 4 pages

2. Holt, Mike (April 05, 2004). What is Arc Flash? Retrieved December 22, 2005, from http://www.mikeholt.com/mojonewsarchive/NEC-HTML/HTML/What-is-Arc-Flash~20040512.php

3. OSHA Home Page (n.d.). Occupational Safety and Health Administration – OSHA HOME PAGE. Retrieved December 22, 2005, from http://www.osha.gov

4. National Fire Protection Association. (2005). National Electrical Code (Publication number NFPA 70-2005). Salt Lake City, UT: National Fire Protection Association.

5. National Fire Protection Association. (2004). Electrical Safety In the Workplace (Publication number NFPA 70E-2004). Salt Lake City, UT: National Fire Protection Association.