With an arc temperature of 17,000 K (30,100 ☏), the radiation output is centered at 170 nanometers, in the far UV. Even though the energy level used is fairly low (85 joules), the low-impedance, low-inductance circuit produces a flash of 24,000,000 watts. However, the phenomenon of the arc blast is sometimes used to extinguish the electric arc by some types of self-blast–chamber circuit breakers.ĭefinition A controlled arc-flash, produced in a flashtube. (For example, category-4 arc-flash protection, similar to a bomb suit, is unlikely to protect a person from the concussion of a very large blast, although it may prevent the worker from being vaporized by the intense light of the flash.) For this reason, other safety precautions are usually taken in addition to wearing PPE, helping to prevent injury. For example, personal protective equipment (PPE) can be used to effectively shield a worker from the radiation of an arc flash, but that same PPE may likely be ineffective against the flying objects, molten metal, and violent concussion that the arc blast can produce. Both are part of the same arc fault, and are often referred to as simply an arc flash, but from a safety standpoint they are often treated separately. An electric arc between two nailsĪn arc flash is the light and heat produced as part of an arc fault, a type of electrical explosion or discharge that results from a connection through air to ground or another voltage phase in an electrical system.Īrc flash is distinctly different from the arc blast, which is the supersonic shockwave produced when the uncontrolled arc vaporizes the metal conductors. Question/comments? Contact Electrical Safety (371-7886) 1.0/sp00e230.xls (5/07) 1.0/sp00e230.xls (5/07) HESP Arc Flash Calculator Arc-In-Box energy = cal/cm2 at specified working distance Flash Protection Boundary (inches) where arc incident energy = 1.For the related medical problem that can be caused by this, see Arc eye. If any doubts exist on use of this spreadsheet, or to perform a flash hazard analysis on systems operating at more than 1000 volts, consult with an electrical engineer or other knowledgeable person. While the testing and development of methods is not complete this proposal contains methods that reflect significantly more laboratory data than the existing methods and will allow improved safety.” This calculator is for use only with systems operating at less than 1000 volts. Recent testing has enabled development of improved equations for calculating the arc flash incident energy at the arc flash boundary. Public review and comments are strongly encouraged. According to the NFPA 70E Technical Committee on Electrical Safety Requirements for Employee Workplaces, “This proposal presents the best information available to date on arc fault hazards. Arc flash calculation is not an exact science and caution is always necessary, including use of multiple alternate methods that are available to verify results and ensure the highest level of safety based on the best information available. This spreadsheet is not intended to replace existing up to date fault studies or support of experienced electrical engineers, but is one tool that can assist engineers, planners, and electrical safety POCs in performing a flash hazard analysis. Electrical engineering should be consulted to obtain information on fault clearing times. That is the fault current value that is used to determine the clearing time of the overcurrent protective device ahead of the potential arc fault location. An IEEE 1584 equation is used to calculate arcing fault current. This tool uses methods that have been shown to result in conservative estimates of fault current, which should result in conservative estimates of arc incident energy if appropriate arc fault clearing times are used. 1.0/sp00e230.xls (5/07) Hanford Electrical Safety Program Arc Flash Calculator This Excel file combines arc flash equations from a proposal to NFPA 70E-2003 with simplified equations to calculate available fault current.
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