![]() ![]() IEEE 1584 Method (for AC systems up to 15kV).Doughty Neal (for AC systems up to 600V).Several methodologies for calculating arc flash incident energy have been developed over the years, including: What are the recognised Incident Energy calculation methodologies? This allows for less restrictive and expensive PPE to be selected. This is to ensure that the best safegaurds against arc flash have been employed and the Incident Energy lowered wherever practical. ![]() However, PPE should always be considered as a last resort and it is important to explore other risk mitigation measures following completion of an Arc Flash Study. At a basic level Arc Flash PPE should be selected with an Arc Rating greater than the calculated Incident Energy the worker could be exposed to. The Working Distance and Arc Flash Boundary are shown in the following illustration:Īlthough more generally used as part of the arc flash risk assessment process, the calculated Incident Energy can also be used to determine PPE requirements. Once inside the AFB, suitably-rated Arc Flash PPE should be worn to protect the worker for situations and activities where it has been determined that there is a likelihood of an arc flash occuring. This value of heat energy will cause 2nd degree burns to bare skin when it is exposed for a duration of 1 second. The AFB is the distance away from the arc at which the heat energy experienced will be 1.2 cal/cm 2. The Arc Flash Boundary (AFB) is also calculated as part of an Arc Flash Study. It is important to recognise that the Incident Energy will be greater at a distance less than the Working Distance. The IE, typically expressed in calories per square centimeter (cal/cm 2) is a quantitative evaluation of the severity of an Arc Flash and can be used in a formal risk assessment process. This is the distance from the arc to the worker's head and torso, which are the areas of the body most at risk from severe burns. The IE is determined at a specified distance away from the arc itself - this is called the Working Distance. A recognised methodology is used to calculate the thermal energy that someone working on the equipment will be subjected to during the incident – this is called the Incident Energy (IE). ![]()
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