Without the right protection equipment covering your entire body, the safe distance you must be is the arc flash boundary. So still not super safe, but not life threatening.Īrc flash PPE protects against the short burst of intense radiant heat that is released from an arc up close. With an arc flash boundary that hazard is the onset of a 2 nd degree burn. In the safety world, a boundary is an approach limit to a hazard.

The largest boundary sets the approach limit and determines where a barricade should be set up to alert others. Typically, the arc flash boundary is the largest boundary, but in some cases the shock hazard limited approach boundary can be larger. For more on Arc Flash ‘Working Distance’ and Shock Approach Boundaries, see this post, Arc Flash Boundary: Working Distance & Approach Distance Explained We’ll look at how that safe distance is communicated, where it comes from, what it means, and who’s responsible for it. For everyone else that means keeping a safe distance. For electricians, this means wearing the right PPE when they get up to work. We’re going to look at the arc flash hazard. Essentially the closer you are to the arc the hotter it gets.įor someone working on or near exposed parts that have an arc flash hazard, the important thing to know is how bad it could be…this is called the ‘Incident Energy’. It anyone has an comments or spots any errors in the above, please chip in below.With electrical equipment there are two main hazards to consider, shock and arc flash. To make life a little easier I have created a calculator to do the grunt work. To carry out arc flash calculations, first workout the arcing current, then the incident energy and finally the arc flash boundary. The limit of 5.0 J/cm 2 is that at which a person is likely to receive second degree burns. X = is a distance exponent from the table aboveĮ B can be set at 5.0 J/cm 2 for bare skin or at the rating of any proposed PPE. Knowing the incident energy, the flash boundary distance is given by:ĭ B = 1 x- voltages ≤ 15 kV and gaps ≤ 152 mmĭ B = 2.142 × 10 6 V I b f ( t E B )- voltages > 15 kV or gaps > 152 mmĬ f= 1.0 for voltages greater than 1000 V and 1.0 for voltages less than 1000 V The flash boundary is the distance from the arc point to a location when the incident energy is less than a given value. Note: to convert J/cm 2 to cal/cm 2 multiply by 0.239 Gap and distance factors Note: for voltages greater than 15 kV, it is not necessary to first calculate E n X = is a distance exponent from the table belowĮ = 2.142 × 10 6 V I b f ( t D 2 ) - voltages > 15 kV or gaps > 152mm K 2 = 0 for ungrounded or high resistance ground systems and -0.113 for grounded systemsĮ = 4.184 C f E n ( t 0.2 ) ( 610 x D x ) - voltages ≤ 15 kV and gaps ≤ 152 mmĬ f = 1.0 for voltages greater than 1000 V and 1.5 for voltages less than 1000 V K 1 = -0.792 for open configurations and -0.555 for boxed configurations The normalized incident energy is given by:

Once the normalized energy has been calculated, this is then adjusted to reflect the actual arcing time and distance. The result of this calculation is the incident energy for a arc duration to 0.2 s and at a distance from the arc point to the person of 610 mm. To calculated the incident energy, first normalized incident energy is calculated. K = -0.153 for open configurations and -0.097 for box configurations

In order to determine both the flash protection boundary and incident energy, first the arcing current needs to be calculated. I bf - bolted three phase fault current (kA)Į B - incident energy at boundary distance (J/cm 2)Į n - normalized incident energy (J/cm 2)Ĭ B - distance of boundary from arc point (mm) Arcing Current 1584 'IEEE Guide for Performing Arc-Flash Hazard Calculations'. I will be looking at the calculation of these two parameters in terms of IEE Std. When evaluating arc flash there are two main considerations, 1) the incident energy in the arc flash and 2) flash protection boundary. Appropriate procedures and personal protective equipment are then employed to minimise potential injuries. To protect people a risk analysis on the arc flash hazard is carried out to better understand what may occur. Quickly expanding air and vaporization of metals causes high pressures, sound and shrapnel leading to multiple types of injuries. In addition to electric shock hazard, fault currents passing through air causes Arc Flash.ĭuring arc flash, temperatures of 20,000 oC for several metres around equipment can exist, resulting in severe burn injuries. Arc FlashWorking in the vicinity of electrical equipment poses an hazard.

Arc flash boundary calculator