Beyond thermal testing
The joint initiative also will break new ground by studying nonthermal phenomena associated with arc flash and the hazards they create. It will look to create an initial arc flash energy balance that includes radiation, pressure, and plasma. Following are some of the approaches planned to reach that goal.
The program will measure the intensity of IR, visible, UV, and other potentially injurious electromagnetic energies in an arcing fault and how they affect the body. It will explore such areas as retinal damage due to visible and UV light and may involve placing detectors behind safety goggles and other eye safety gear during arc flashes. It may also evaluate the effects of brief exposure to ionizing radiation in arc flashes.
Because little test or injury data on the high-pressure fronts created in arc blasts are available, the program will seek basic data on their intensity and consequences. It will record sound pressures and frequencies at various distances, angles, and times from a flash source, as well as the injury potential of these waves and how well shields and hoods attenuate them. Other tests will include comparing pressure waves in open areas and enclosures and determining blast pressures in arcs interrupted in one cycle or less. The program will also seek to relate the substantial understanding of pressure waves created by explosives to those formed in arc blasts.
The program will evaluate the shrapnel and molten metal ejected during arc faults. It will create a database for arc flash shrapnel injuries, to allow the frequency and severity of these injuries to be defined. It also will formulate arc flash shrapnel test protocols and use them to relate shrapnel mass and velocity to electrical parameters.
The program will also conduct pioneering research into the toxic and corrosive particles and vapors present in arc flash plasmas and how they impact personnel and PPE. This will involve determining the feasibility of generating toxic materials in laboratory-generated arc flashes and finding ways to define the amount and type of materials generated. This is a challenging area of study, given the variability of the mass, composition, and temperature of arc flash plasma clouds.
The program will evaluate arc flash events in direct current systems, which are commonplace in some industries and which are increasing as the demand for battery back-up energy in information technology systems increases. This part of the program also calls for developing a method to evaluate arcing faults in DC systems.
Finally, enclosure testing will seek to expand current understanding of how enclosures, their doors, and the equipment they contain affect arc flash properties and the potential for injury. Testing of "arc in a box" events will consider such factors as enclosure size and shape, door construction, arc location and orientation, electrical system capacity, grounding, protective-device bus orientation and spacing, and the components contained in the box.
Current PPE and work practices tend to focus on the thermal and radiative effects of arc flash, so they may not protect well against pressure waves, plasma, or shrapnel. An underlying, ongoing theme of the joint initiative will be to understand how well gloves, safety goggles, flame-resistant clothing, safety shoes, and other PPE items protect workers against the full range of arc flash and blast hazards.
Who will benefit
Electricians, mechanics, HVAC personnel, and other plant workers are at risk from arc flash when they work on panel boards, motor control centers, switchgear, transformers, and many other power system elements. Although lockout/tagout programs help prevent arc flash events, they do not eliminate them.
Arcing faults can occur through human error, especially during voltage testing and system shutdown and start-up. Bear in mind that a circuit may remain energized even after it is believed to be shut down because of inaccurate signs and labels, worker confusion, faulty wiring, or poor work practices. Arcing faults might result from damaged insulation, accidental contact with energized components, equipment with incorrect short-circuit ratings, and corrosion and impurities that provide a current path.
Because arc flash and arc blast are ever-present hazards for anyone working on or near electrical equipment, the IEEE/NFPA Arc Flash Collaborative Research Project will be an intensive effort to gain deeper insight into these phenomena. This knowledge will then help create better industry safety standards, work practices, PPE, and equipment to help reduce electrical injuries, fatalities, and property damage. The effort will benefit all stakeholders in the electric power industry, from utilities to equipment and PPE vendors to regulatory agencies and insurers.
The data and recommendations from the joint initiative will help the IEEE and NFPA strengthen arc flash safety standards—specifically, IEEE 1584, "Guide for Performing Arc-Flash Hazard Calculations," and NFPA 70E, "Standard for Electrical Safety in the Workplace." IEEE 1584 provides methods for determining the flash hazard area and how much energy workers can potentially be exposed to when working on or near electrical equipment. NFPA 70E, which is widely cited by OSHA, covers work practices such as employee training, risk evaluation, safe work conditions, approach boundaries, and PPE use. In addition, it is anticipated that the data and recommendations will lead to improvements in electrical equipment and power system designs, enhancements in maintenance tools, instruments, and work practices, and advances in personal protection technology.
The more-refined understanding of arc flash phenomena, and the gains in on-the-job safety that it will make possible, will help companies boost operating efficiency and productivity. It will enable more effective PPE, safer equipment, and better training. Better protection from arc flash also promises to decrease expenses for injuries and property damage, lower insurance claims and premiums, and reduce litigation and workers' compensation claims.
—Those interested in learning more about, or contributing to, the IEEE/NFPA Arc Flash Collaborative Research Project should contact Sue Vogel at IEEE (732-562-3817, s.vogel@ieee.org) or Mark Earley at NFPA (617-984-7400, mwearley@nfpa.org). A prospectus on the project is available online at http://standards.ieee.org/esrc/arcflash/index.html.
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Comments (1)
It may be over conservative, but is this the intent of the definition? There is concern for ventilated switchgear in particular because the path of the arc flash cannot be accurately predicted.