| There continues to be a great deal of activity | | | | number. If these additional impedances are not |
| surrounding the update to NFPA 70E scheduled to | | | | included in the calculations, then the incident |
| be published in October 2008. For the proposed | | | | energy levels may be under-estimated. |
| 2008 edition of NFPA 70, National Electrical | | | | Short-circuit current levels in electric utility |
| Code® (NEC®), the Technical Correlating | | | | systems are continuously changing as both |
| Committee (TCC) received 3,668 proposals and | | | | electricians and maintenance workers replace over |
| 3,206 comments during the revision cycle. For | | | | current devices, fuses and panel boards or |
| those of us involved in working with energized | | | | upgrades are made to the system. Any of |
| electrical circuits the outcome of the new | | | | theses changes can have an effect on the |
| standards will likely impact how we do our job. | | | | arc-flash energy level, but may not be noted on |
| The goal is to increase safety through well | | | | the warning label. |
| thought through practices. | | | | Step 2. Provide Protective Clothing |
| How are Thermographers Addressing the Issue? | | | | The next step is to ensure that anyone working |
| Increasing the distance at which inspections of | | | | on equipment that might generate arc flash wear |
| open cabinets are performed. | | | | protective clothing, including fire retardant suits, |
| Most cameras offer telephoto lens that enable | | | | gloves, face shield/goggles and other gear as |
| the thermographer to stand 2 to 3 times further | | | | provided by the standards. |
| away from the energized components while | | | | Step 3. Equipment That Limits Exposure |
| maintaining the same resolution. In addition newer | | | | Although no single piece of equipment can |
| high definition cameras will provide the same | | | | completely eliminate arc flash hazards, making it |
| performance as 320x240 array based cameras | | | | convenient to perform most routine maintenance |
| at twice the normal standoff. | | | | tasks without directly accessing the equipment |
| New Language Being Drafted by NFPA and ASTM | | | | can significantly reduce the risk. Providing external |
| ASTM E-1934 | | | | plug-ins to equipment inside an enclosure is one |
| New language is being proposed in the next | | | | approach. Properly designed and insulated panels |
| version of ASTM E-1934, Standard of Examining | | | | that are wired to the appropriate equipment inside |
| Electrical Power Distribution Equipment with | | | | allows operators to change settings and monitor |
| Infrared Technology. 7.5 - As an alternative, | | | | performance without opening the enclosure. With |
| consideration may be given to conducting the | | | | a traditional disconnect switch inside the main |
| examination through "windows" that are | | | | enclosure, live power is still present on the line side |
| transparent to detected infrared radiation or to | | | | of the disconnect switch. Since live power is still |
| "ports." Safety procedures should be modified to | | | | being fed upstream to the disconnect switch on |
| accommodate this task. Care must be taken to | | | | the panel, the threat of an arc flash incident |
| insure that all equipment can be seen and special | | | | remains. Another approach is to develop |
| lenses may be required. | | | | arc-resistant electrical cabinets designed to contain |
| Did You Know? | | | | the arc energy and direct it away from |
| Incident energy from an arc flash created with | | | | personnel- - they cannot prevent an arc flash. |
| vertical, unterminated conductors in a cabinet (20" | | | | "Arc-resistant" describes equipment designed to |
| x 20" x 20") decreases by the inverse of the | | | | control arc flash exposure by extinguishing the |
| distance to the 1.5 power. If the arc has horizontal | | | | arc, by controlling the spread of the arc or by |
| conductors that point out of the cabinet opening | | | | channeling the arc pressure wave away from |
| or vertical which terminate into an insulated | | | | personnel. Arc-resistant designs represent |
| barrier, the exposure may decrease by a lower | | | | enhanced safety technology and, therefore, an |
| exponent, but not enough data has been collected | | | | enhanced level of safety." The design redirects |
| on these conductor configurations. - Tom Neal of | | | | arc flash energy out relief vents at the top of the |
| Neal Associates | | | | unit and away from personnel through an |
| Next Revision of NFPA 70E | | | | overhead plenum. These products have been |
| The following new language has been submitted | | | | successfully tested in accordance with ANSI |
| to, and is being considered, by the 70E | | | | C37.20.7: IEEE Guide for Testing Medium-Voltage |
| committee: "When access to conduct such | | | | Metal- Enclosed Switchgear for Internal Arcing |
| inspections of energized equipment is limited by | | | | Faults. During testing, cotton squares (similar to |
| the appropriate use of special windows or small | | | | 4.5 oz/yard untreated T-shirt material) are |
| access ports, rather than by gaining access | | | | mounted a meter from the MCC. Acceptance |
| though opening the enclosure door, the limit of the | | | | criteria require that none of the cotton indicators |
| approach, and the required PPE, will be the same | | | | ignite during or following a test. To redirect the |
| as if the enclosure door were left unopened." | | | | arc exhaust gases, specialized silicone coated, |
| Increased diligence of OSHA | | | | aluminum pressure relief vents on the unit's roof |
| Although it is only referenced in OSHA 29 CFR | | | | open to release the pressure. A plenum system |
| Part 1910 Subpart S, Appendix A, NFPA 70E is | | | | above the enclosure channels the superheated |
| considered by OSHA to be the recognized | | | | gas and vaporized copper and steel to a safe and |
| industry practice for electrical safety. | | | | controlled location. |
| Role of NFPA | | | | Standards Organizations and Arc Flash Protection |
| OSHA standards don't provide details on how to | | | | To protect operators, OSHA and NFPA 70E |
| conduct an electrical hazard assessment or how | | | | standards require a "flash protection boundary." |
| to select PPE. For guidance on compliance, you | | | | OSHA has adopted the National Fire Protection |
| need to look to national consensus standards. | | | | Association's "70E Standards for Electric Safety in |
| NFPA is one of the foremost consensus | | | | the Workplace" as an acceptable means of |
| standards for electrical safety. It covers | | | | compliance to meet this requirement. Section |
| employee protection from the electrical hazards | | | | 1910.333 of Subpart S states: "Safety-related |
| of shock, arc flash and arc blasts. | | | | work practices shall be employed to prevent |
| NFPA Compliance Part I - Installation Safety | | | | electrical shock or other injuries resulting from |
| Requirements | | | | either direct or indirect electrical contacts". |
| Covers safety requirements for the design and | | | | Therefore companies should take great lengths to |
| installation of electric conductors and equipment. | | | | ensure that electrical workers are safe from |
| Essential to the proper use of Part I of this | | | | arc-flash dangers. |
| standard is the understanding that it is not | | | | References: |
| intended to be applied as a design, installation, | | | | Organizations Involved In This Work |
| modification, or construction standard for an | | | | NFPA - The National Fire Protection Agency |
| electrical installation or system. Its content has | | | | The mission of the international nonprofit NFPA is |
| been intentionally limited in comparison to the | | | | to reduce the worldwide burden of fire and other |
| content of the NEC in order to apply to an | | | | hazards on the quality of life by providing and |
| electrical installation or system as part of an | | | | advocating consensus codes and standards, |
| employee's workplace. This standard is compatible | | | | research, training, and education. NFPA |
| with corresponding provisions of the NEC, but is | | | | membership totals more than 81,000 individuals |
| not intended to, nor can it, be used in lieu of the | | | | from around the world and more than 80 national |
| NEC. | | | | trade and professional organizations. Established in |
| Part 2 - Safety Related Work Practices | | | | 1896, NFPA serves as the world's leading |
| Covers electrical safety related work practices | | | | advocate of fire prevention and is an authoritative |
| and procedures for employees who work on or | | | | source on public safety. In fact, NFPA's 300 codes |
| near exposed energized electrical conductors or | | | | and standards influence every building, process, |
| circuit parts. Electrical hazard includes arc flash. | | | | service, design, and installation in the United |
| Relevant requirements include: | | | | States, as well as many of those used in other |
| - Power must be proven to be off before | | | | countries. NFPA's focus on true consensus has |
| performing work. This includes: | | | | helped the association's code-development |
| - The safe interruption of the load and opening of | | | | process earn accreditation from the American |
| the disconnect | | | | National Standards Institute (ANSI). |
| - Visual verification/voltage testing to ensure | | | | OSHA - Occupational Safety & Health |
| deenergization | | | | Administration |
| The potential electrical hazard must be identified | | | | OSHA's mission is to send every worker home |
| and documented | | | | whole and healthy every day. Since the agency |
| Flash hazard analysis must be performed | | | | was established in 1971, workplace fatalities have |
| Flash protection boundaries must be determined | | | | been cut by 62 percent and occupational injury |
| Appropriate steps must be taken to protect | | | | and illness rates have declined 40 percent. At the |
| persons working near live parts or within the flash | | | | same time, U.S. employment has nearly doubled |
| protection boundary | | | | from 56 million workers at 3.5 million worksites to |
| Personal Protective Equipment must be provided, | | | | 115 million workers at nearly 7 million sites. |
| based on the relevant incident energy exposure | | | | ASTM |
| levels (cal/cm2) | | | | ASTM International (Originally known as the |
| Only properly qualified persons shall be allowed to | | | | American Society for Testing and Materials) is one |
| perform work | | | | of the largest voluntary standards development |
| Part 3 - Safety Related Maintenance | | | | organizations in the world-a trusted source for |
| Requirements | | | | technical standards for materials, products, |
| Covers practical safety-related maintenance | | | | systems, and services. Known for their high |
| requirements for electrical equipment and | | | | technical quality and market relevancy, ASTM |
| installations in workplaces. | | | | International standards have an important role in |
| Part 4 - Safety Requirements for Special | | | | the information infrastructure that guides design, |
| Equipment | | | | manufacturing and trade in the global economy. |
| Covers electrical safety installation requirements | | | | IEEE - IEEE Electrical Safety |
| and safety-related work practices and procedures | | | | A predominant area of standards activity within |
| for employees who work on or near special | | | | the IEEE-SA addresses technology and related |
| electrical equipment such as electrolytic cells. | | | | safety needs for the power and energy industry |
| Preventing Arc Flash Incidents | | | | and subsequent industry applications. A key |
| Step 1. Perform Hazard Assessment and Create | | | | component to electrical safety is for those |
| Warning Labels | | | | working with electrical current and within |
| The label is the first step. However, determining | | | | environments using electrical current to be |
| the arc-flash levels may change as routine | | | | abreast of standards and regulations that include |
| maintenance and repair is performed. The level of | | | | safety best practices. It is critical for employees |
| arc-flash hazard of any piece of equipment | | | | to familiarize themselves with these documents |
| depends on the level of arc-fault current and the | | | | and the organizations responsible for developing |
| time it takes to trip the nearest upstream over | | | | them. The IEEE, namely via its Color Books |
| current protection device. In most cases, a local | | | | Standards for Industrial and Commercial Power |
| utility engineer can determine the fault current | | | | Systems and the National Electrical Safety Code, |
| levels; however these fault current values may | | | | as well as its Power Engineering standards, is a |
| be based on the impedance of the transformer | | | | major developer of standards that directly or |
| that serves the facility, and additional impedances | | | | indirectly address electrical safety within specific |
| upstream of the transformer can lower the | | | | applications or environments. |