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It happens quite often in practice that work has to be performed in an electrical installation (distribution station, switching room, etc.). Examples of this work are racking in/out the withdrawable circuit breaker unit, replacement of a fuse and so on. Sometimes things can go wrong during the work in the installation (due to human error and/or defect in the installation) and a short circuit can occur. The short circuit shows itself in the form of an arc that can have various effects on the working personnel. The arc flash phenomena include very strong light, shock wave and very loud sound blast (can be compared to that of an explosion). Also a lot of thermal energy is released that can cause serious burns to the personnel.

 

There exist two methods for calculation of the thermal arc flash energy (incident energy):

•IEEE 1584 method: according to “IEEE Guide for Performing Arc-Flash Hazard Calculations”;

•closed box test method of ISSA: “Guideline for the selection of personal protective equipment when exposed to the thermal effects of an electric fault arc”.

 

Both methods are based mainly on the results of experiments. The choice between two methods is possible via Options (F11, tab Calculation | Arc flash).