Arc flask boundary at 480 V

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\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ - (ii) You must ground 2-wire DC systems operating at over 50 volts through 300 volts between conductors: - (A) They supply only industrial equipment in limited areas and are equipped with a ground detector; - (B) They are rectifier-derived from an AC system complying with (a)(iii) through (v) of this subsection; or - (C) They are fire-alarm circuits having a maximum current of 0.030 amperes; - (iii) You must ground AC circuits of less than 50 volts if they are installed as overhead conductors outside of buildings or if they are supplied by transformers and the transformer primary supply system is ungrounded or exceeds 150 volts to ground; - (iv) You must ground AC systems of 50 volts to 1000 volts under any of the following conditions, unless exempted by (a)(v) of this subsection: - (A) If the system can be so grounded that the maximum voltage to ground on the ungrounded conductors does not exceed 150 volts; - (B) If the system is nominally rated three-phase, four-wire wye connected in which the neutral is used as a circuit conductor; - (C) If the system is nominally rated three-phase, four-wire delta connected in which the midpoint of one phase is used as a circuit conductor; or - (D) If a service conductor is uninsulated; - (v) AC systems of 50 volts to 1000 volts are not required to be grounded under any of the following conditions: - (A) If the system is used exclusively to supply industrial electric furnaces for melting, refining, tempering, and the like; - (B) If the system is separately derived and is used exclusively for rectifiers supplying only adjustable speed industrial drives; - (C) If the system is separately derived and is supplied by a transformer that has a primary voltage rating less than 1000 volts, provided all of the following condition…

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Oregon Occupational Safety and Health Division Oregon Administrative Rules AO 2-2017 Division 2 Note 2 to paragraph (8)(b): This paragraph does not require the employer to estimate the incident heat energy exposure for every job task performed by each employee. The employer may make broad estimates that cover multiple system areas provided the employer uses reasonable assumptions about the energy-exposure distribution throughout the system and provided the estimates represent the maximum employee exposure for those areas. For example, the employer could estimate the heat energy just outside a substation feeding a radial distribution system and use that estimate for all jobs performed on that radial system. - (c) The employer must ensure that each employee who is exposed to hazards from flames or electric arcs does not wear clothing that could melt onto their skin or that could ignite and continue to burn when exposed to flames or the heat energy estimated under paragraph (8)(b) of this rule. - Note to paragraph (8)(c) of this rule: This paragraph prohibits clothing made from acetate, nylon, polyester, rayon and polypropylene, either alone or in blends, unless the employer demonstrates that the fabric has been treated to withstand the conditions that may be encountered by the employee or that the employee wears the clothing in such a manner as to eliminate the hazard involved. - (d) The employer must ensure that the outer layer of clothing worn by an employee, except for clothing not required to be arc rated under paragraphs (8)(e)(A) through (8)(e)(E) of this rule, is flame resistant under any of the following conditions: - (A) The employee is exposed to contact with energized circuit parts operating at more than 600 volts, - (B) An electric arc could ignite flammable material in the work area that, in turn, could ignite the employee's clothing, - (C) Molten metal or electric arcs from faulted conductors in the work area could ignite the employee's clothing, or…

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\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ - (i) Employees' hands must not be wet when plugging and unplugging flexible cords and cord- and plug-connected equipment, if energized equipment is involved. - (ii) You must only handle energized plug and receptacle connections with insulating protective equipment if the condition of the connection could provide a conducting path to the employee's hand (if, for example, a cord connector is wet from being immersed in water). - (iii) You must properly secure locking-type connectors after connection. ## (2) Electric power and lighting circuits . - (a) Routine opening and closing of circuits . You must use load rated switches, circuit breakers, or other devices specifically designed as disconnecting means for the opening, reversing, or closing of circuits under load conditions. You must not use cable connectors not of the load-break type, fuses, terminal lugs, and cable splice connections for such purposes, except in an emergency. - (b) Reclosing circuits after protective device operation . After a circuit is deenergized by a circuit protective device, you must not manually reenergize the circuit until it has been determined that the equipment and circuit can be safely energized. The repetitive manual reclosing of circuit breakers or reenergizing circuits through replaced fuses is prohibited. Note: When it can be determined from the design of the circuit and the overcurrent devices involved that the automatic operation of a device was caused by an overload rather than a fault condition, no examination of the circuit or connected equipment is needed before the circuit is reenergized. - (c) Overcurrent protection modification . You must not modify overcurrent protection modification overcurrent protection of circuits and conductors, even on a temporary …

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\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ - (b) Services over 600 volts, nominal . The following additional requirements apply to services over 600 volts, nominal. - (i) You must guard service-entrance conductors installed as open wires to make them accessible only to qualified persons. - (ii) You must post signs warning of high voltage where unqualified employees might come in contact with live parts. ## Overcurrent protection . - (a) 600 volts, nominal, or less . The following requirements apply to overcurrent protection of circuits rated 600 volts, nominal, or less. - (i) You must protect conductors and equipment from overcurrent in accordance with their ability to safely conduct current. - (ii) Except for motor running overload protection, overcurrent devices may not interrupt the continuity of the grounded conductor unless all conductors of the circuit are opened simultaneously. - (iii) You must provide a disconnecting means on the supply side of all fuses in circuits over 150 volts to ground and cartridge fuses in circuits of any voltage where accessible to other than qualified persons so that each individual circuit containing fuses can be independently disconnected from the source of power. However, a current-limiting device without a disconnecting means is permitted on the supply side of the service disconnecting means. In addition, a single disconnecting means is permitted on the supply side of more than one set of fuses as permitted by the exception in WAC 296-24-[redacted postal code] (10)(d)(vi) for group operation of motors, and a single disconnecting means is permitted for fixed electric space-heating equipment. - (iv) Overcurrent devices must be readily accessible to each employee or authorized building management personnel. These overcurrent devices may not be located where the…

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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 - Guarded. Covered, fenced, enclosed, or otherwise protected, by means of suitable covers or casings, barrier rails or screens, mats, or platforms, designed to minimize the possibility, under normal conditions, of dangerous approach or inadvertent contact by persons or objects. Note to the definition of "guarded" : Wires that are insulated, but not otherwise protected, are not guarded. Insulated. Separated from other conducting surfaces by a dielectric (including air space) offering a high resistance to the passage of current. Note to the definition of "insulated" : When any object is said to be insulated, it is understood to be insulated for the conditions to which it normally is subjected. Otherwise, it is, for the purpose of this section, uninsulated. - Isolated. Not readily accessible to persons unless special means for access are used. - Statistical sparkover voltage. A transient overvoltage level that produces a 97.72-percent probability of sparkover (that is, two standard deviations above the voltage at which there is a 50-percent probability of sparkover). - Statistical withstand voltage. A transient overvoltage level that produces a 0.14percent probability of sparkover (that is, three standard deviations below the voltage at which there is a 50-percent probability of sparkover). - B. Installations energized at 50 to 300 volts. The hazards posed by installations energized at 50 to 300 volts are the same as those found in many other workplaces. That is not to say that there is no hazard, but the complexity of electrical protection required does not compare to that required for highvoltage systems. The employee must avoid contact with the exposed parts, and the protective equipment used (such as rubber insulating gloves) must provide insulation for the voltages involved. - C. Exposed energized parts over 300 volts AC. [redacted phone](3)(a) requires …