It details the incident energy at the panel and the working distance, the arc flash boundary and the nominal voltage of that equipment. Note: the above distances may be different to those stated in company operational safety rules, DNO standards or transmission standards.Ĭonsider the arc flash warning label above which contains important information. Restricted Approach Boundary Includes Inadvertent Movement Adder Nominal System Voltage Range, Phase to Phase The table below has been adapted from NFPA 70E, Table 130.4(E)(a) Shock Protection Approach Boundaries to Exposed Energised Electrical Conductors or Circuit Parts for Alternating Current Systems. In Europe we would know this person as an electrically skilled or instructed person, in other words a competent person, again stating the minimum distance that should be maintained from exposed live parts in order to prevent electric shock. Restricted Approach Boundary- approach by a Qualified Person. Typically, in the UK, switchpanels contain live parts within enclosure and it is only when such enclosures are open and live parts are accessible does an issue exist. In Europe we would know this as an ordinary person, that being a person who is neither electrically skilled nor instructed and is the minimum distance that a non-competent person can approach parts that are energized and dangerous. Limited Approach Boundary- approach by Unqualified Persons. This article looks at the arc flash boundary, however, before moving on it is work discussing the limited and restricted approach boundaries that in fact relate to electric shock protection, rather than arc flash control. Dependant on the remit of any arc flash study carried out, labels fitted to switchgear may make reference to one, or all of the above boundaries. Arc Flash Boundary DistancesĪccording to NFPA 70E, three boundaries exist, these are Limited Approach Boundary, Restricted Approach Boundary and Arc Flash Boundary. (2) The energized electrical conductors or circuit parts are insulated from the qualified person and from any other conductive object at a different potential.Compliance Director, Andy Linley, discusses Arc Flash Boundary distances, what they are and factors affecting them. Insulating gloves and sleeves are considered insulation only with regard to the energized parts upon which work is performed. (1) The qualified person is insulated or guarded from energized electrical conductors or circuit parts operating at 50 volts or more. No qualified person shall approach or take any conductive object closer to exposed energized electrical conductors or circuit parts than the restricted approach boundary set forth in Table 130.4(E)(a) and Table 130.4(E)(b), unless one of the following conditions applies: Under no circumstance shall unqualified person(s) be permitted to cross the restricted approach boundary.ġ30.4(G) Restricted Approach Boundary.

Where there is a need for an unqualified person(s) to cross the limited approach boundary, a qualified person shall advise the unqualified person(s) of the possible hazards and continuously escort the unqualified person(s) while inside the limited approach boundary.

(3) Entering the Limited Approach Boundary. Where one or more unqualified persons are working at or close to the limited approach boundary, the alerting methods in 130.7(E) shall be applied to advise the unqualified person(s) of the electrical hazard and warn him or her to stay outside of the limited approach boundary. (2) Working at or Close to the Limited Approach Boundary. Unless permitted by 130.4(F)(3), no unqualified person shall be permitted to approach nearer than the limited approach boundary of energized conductors and circuit parts. Once there, click on the free access link to NFPA 70E. For the complete section, see the actual NFPA 70E text at NFPA.ORG. The shock protection boundaries and the arc flash boundary are completely different and independent of each other.īelow is a sample of NFPA 70E. It is critical to understand that in certain instances, the arc flash boundary might be a greater distance from the energized electrical conductors or circuit parts than the limited approach boundary.

Table 130.4(E)(b) is used for the distances associated with DC system voltages.

Table 130.4(E)(a) is used for the distances associated with AC system voltages.

These boundaries are determined from using two separate tables: In Section 130.4(E) of NFPA 70E, there are two shock protection boundaries that apply to personnel approaching exposed energized electrical conductors or circuit parts:

Arc flash approach boundaries