arc flash

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Division 2 AO 2-2017 Oregon Administrative Rules Oregon Occupational Safety and Health Division Incident heat energy for single-phase-to-ground exposures. Table 4 and Table 5 provide incident heat energy levels for open-air, phase-to-ground electric-arc exposures typical for overhead systems. Table 6 presents estimates of available 2 energy for employees using rubber insulating gloves to perform work on overhead systems operating at 4 to 46 kilovolts. The table assumes that the employee will be 380 millimeters (15 inches) from the electric arc, which is a reasonable estimate for rubber insulating glove work. Table 6 also assumes that the arc length equals the sparkover distance for the maximum transient overvoltage of each voltage range. 3 To use the table, an employer would use the voltage, maximum fault current, and maximum clearing time for a system area and, using the appropriate voltage range and fault-current and clearingtime values corresponding to the next higher values listed in the table, select the appropriate heat energy (4, 5, 8, or 12 cal/cm 2 ) from the table. For example, an employer might have a 12,470-volt power line supplying a system area. The power line can supply a maximum fault current of 8 kiloamperes with a maximum clearing time of 10 cycles. For rubber glove work, this system falls in the 4.0-to-15.0-kilovolt range; the next-higher fault current is 10 kA (the second row in that voltage range); and the clearing time is under 18 cycles (the first column to the right of the fault current column). Thus, the available heat energy for this part of the system will be 4 cal/cm 2 or less (from the column heading), and the employer could select protection with a 5-cal/cm 2 rating to meet [redacted phone](8)(e). Alternatively, an employer could select a base incident-energy value and ensure that the clearing times for each voltage range and fault current listed in the table do not exceed the corresponding clearing time specified in the table. F…

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Division 2 AO 2-2017 Oregon Administrative Rules Oregon Occupational Safety and Health Division [redacted phone](8)(e) requires employers, in certain situations, to select protective clothing and other protective equipment with an arc rating that is greater than or equal to the incident heat energy estimated under [redacted phone](8)(b). Based on laboratory testing required by ASTM F1506-10a, the expectation is that protective clothing with an arc rating equal to the estimated incident heat energy will be capable of preventing second-degree burn injury to an employee exposed to that incident heat energy from an electric arc. Note that actual electric-arc exposures may be more or less severe than the estimated value because of factors such as arc movement, arc length, arcing from reclosing of the system, secondary fires or explosions, and weather conditions. Additionally, for arc rating based on the fabric's arc thermal performance value (ATPV), a worker exposed to incident energy at the 5 arc rating has a 50-percent chance of just barely receiving a second-degree burn. Therefore, it is possible (although not likely) that an employee will sustain a seconddegree (or worse) burn wearing clothing conforming to [redacted phone](8)(e) under certain circumstances. However, reasonable employer estimates and maintaining appropriate minimum approach distances for employees should limit burns to relatively small burns that just barely extend beyond the epidermis (that is, just barely a second degree burn). Consequently, protective clothing and other protective equipment meeting [redacted phone](8)(e) will provide an appropriate degree of protection for an employee exposed to electric-arc hazards. [redacted phone](8)(e) does not require arc-rated protection for exposures of 2 cal/cm 2 or less. Untreated cotton clothing will reduce a 2-cal/cm 2 exposure below the 1.2- to 1.5-cal/cm 2 level necessary to cause burn injury, and this material should not ignite at such low he…

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Division 2 AO 2-2017 Oregon Administrative Rules Oregon Occupational Safety and Health Division The employer must determine the maximum anticipated per-unit transient overvoltage, phase-toground, through an engineering analysis, as required by [redacted phone](3)(b), or assume a maximum anticipated per-unit transient overvoltage, phase-to-ground, in accordance with Table RR-8. For phase-to-phase exposures, the employer must demonstrate that no insulated tool spans the gap and that no large conductive object is in the gap. The worksite must be at an elevation of 900 meters (3,000 feet) or less above sea level. - 1 Federal, State, and local regulatory bodies and electric utilities set reliability requirements that limit the number and duration of system outages. - 2 Sparkover is a disruptive electric discharge in which an electric arc forms and electric current passes through air. - 3 The withstand voltage is the voltage at which sparkover is not likely to occur across a specified distance. It is the voltage taken at the 3s point below the sparkover voltage, assuming that the sparkover curve follows a normal distribution. - 4 Test data demonstrates that the saturation factor is greater than 0 at peak voltages of about 630 kilovolts. Systems operating at 345 kilovolts (or maximum system voltages of 362 kilovolts) can have peak maximum transient overvoltages exceeding 630 kilovolts. Table RR-2 sets equations for calculating a based on peak voltage. - 5 For voltages of 50 to 300 volts, Table RR-2 specifies a minimum approach distance of "avoid contact." The minimum approach distance for this voltage range contains neither an electrical component nor an ergonomic component. - 6 For the purposes of estimating arc length, Division 2/RR generally assumes a more conservative dielectric strength of 10 kilovolts per 25.4 millimeters, consistent with assumptions made in consensus standards such as the National Electrical Safety Code (IEEE C2-2012). The more conservative v…

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Division 2 AO 2-2017 Oregon Administrative Rules Oregon Occupational Safety and Health Division - (A) Arc-rated protection is not necessary for the employee's hands when the employee is wearing rubber insulating gloves with protectors or, if the estimated incident energy is no more than 14 cal/cm2, heavy-duty leather work gloves with a weight of at least 407 gm/m2 (12 oz/yd2), - (B) Arc-rated protection is not necessary for the employee's feet when the employee is wearing heavy-duty work shoes or boots, - (C) Arc-rated protection is not necessary for the employee's head when the employee is wearing head protection meeting [redacted phone](9) and 437003-0134(9) if the estimated incident energy is less than 9 cal/cm2 for exposures involving single-phase arcs in open air or 5 cal/cm2 for other exposures, - (D) The protection for the employee's head may consist of head protection meeting [redacted phone](9) and [redacted phone](9), and a faceshield with a minimum arc rating of 8 cal/cm2 if the estimated incident-energy exposure is less than 13 cal/cm2 for exposures involving single-phase arcs in open air or 9 cal/cm2 for other exposures, and - (E) For exposures involving single phase arcs in open air, the arc rating for the employee's head and face protection may be 4 cal/cm2 less than the estimated incident energy. Note to paragraph (8): See Appendix E to Division 2/RR for further information on the selection of appropriate protection. - (9) Fuse handling. When an employee must install or remove fuses with one or both terminals energized at more than 300 volts, or with exposed parts energized at more than 50 volts, the employer must ensure that the employee uses tools or gloves rated for the voltage. When an employee installs or removes expulsiontype fuses with one or both terminals energized at more than 300 volts, the employer must ensure that the employee wears eye protection meeting the requirements of Division 2/I and Division 3/E, uses a tool rated for the …