Arcing current can be expressed as a function of the length of the gap and arcing voltage. Arcing voltage can be derived as a function of arcing current, system voltage and the available fault current. DCAFA V3.0 calculates arcing current using the iterative method by cycling through the equations for arcing current and arcing voltage until the answers converge. Next, the program will determine arc duration based on protective device time-current characteristics and circuit time-constant. Lastly, the program will calculate incident energy at working distance, arc flash and shock protection boundaries.
DCAFA V3.0 comes complete with a built-in library of selected protection devices and the capability to extend the library. The program will determine arc duration based on predicted arcing current value, circuit time constant and selected protection device type and rating. While circuit time constant affects current rise and protective device performing characteristics, it will also have an impact on arc duration. Therefore, time current characteristic of the upstream protective device clearing the fault has to be adjusted for the time constant. If this occurs, the process of determining the protective device operating time is cumbersome. DCAFA V3.0 will cycle through relationships between the effective RMS current, available fault current, number of time constants, analytical expression for the selected protective device time-current characteristic and make proper adjustments to arc duration.