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Arc Flash Analysis
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Arc Flash Hazard CalculatorArc-Flash-Analytic v 3.2 calculates the incident energy and arc flash boundary for any point in a power system.Related Information:Arc-Flash-Analytic v 3.2 software tool has been developed based on IEEE 1584 Guide for Performing Arc-Flash Hazard Calculations as an easy to use and comprehensive instrument for calculating arc incident energy, flash protection boundary, determining limited, restricted and prohibited approach boundaries and risk category required by N.E.C and OSHA when work is to be performed on or near the energized equipment. Also, the calculator allows to calculate initial pressure generated by arc blast and arc flash TNT ( Tri Nitro Toluen / Trotyl ) equivalent.
The IEEE 1584 empirically derived model was chosen for the analyzing arc flash faults since the model is capable to accurately account for variety of setup parameters: open and box equipment configurations, grounding of all types and ungrounded, gap between conductors of 3 to 152 mm., bolted fault currents in the range of 700A to 106kA, system voltages in the range of 208V to 15kV, and working distances. For cases where voltage is over 15kV or gap is outside the range of the model, the theoretically derived Lee method can be applied and it is now included in the Arc Flash Analytic v3.2. The calculator also includes IEEE 1584 Fuse Equations for calculating arc flash energies for equipment protected with current limiting Class L and Class RK1 fuses as well as IEEE 1584 Circuit Breaker Equations for calculating arc flash energies for equipment protected with low voltage circuit breakers. Reference data listing most typical configurations and detailed procedure for IEEE 1584 based arc flash calculations has been included in the calculator.
Empirical Model - Main program screen.
When the IEEE 1584 Empirically Derived Model mode is activated, the calculator takes equipment configuration, gap between electrodes, grounding type, short circuit fault current value and system voltage on input, and determines arcing fault current at potential point of fault. Next, the incident energy, flash protection boundary and level of personnel protective equipment are determined based on equipment configuration, arc duration and working distance. For protective devices operating in the steep portion of their time-current curves, a small change in current causes a big change in operating time. Incident energy is linear with time, so arc current variation may have a big effect on incident energy. The IEEE 1584 solution is to make two arc current and energy calculations: one using the calculated expected arc current and one using a reduced arc current that is 15% lower.
Empirical Model - Intermediate Results.
The calculator makes possible both calculations for each case considered. The IEEE 1584 Empirically Derived Model procedure for system voltages less than 15kV requires that an operating time be determined for both the expected arc current and the reduced arc current. Incident energy is calculated for both sets of arc currents and operating times and the larger incident energy is taken as the model result. This solution was developed by comparing the results of arc current calculations using the best available arc current equation with actual measured arc current in the test database. The calculator predicts arcing fault current for a given configuration and bolted fault short circuit current. It also predicts bolted fault current required to cause 15% reduction of the predicted arcing current for the given configuration.
Empirical Model - Final Results.
It was found to be difficult to calculate incident energy in circuits protected by current-limiting fuses because of the reduced arc time and limited let-through current. Therefore, tests were conducted to determine the effect of current-limiting fuses on incident energy. Formulae for calculating arc-flash energies for use with current-limiting Class L and Class RK1 fuses have been developed. These formulae were developed based upon testing at 600 V and a distance of 455 mm (18in.) using one manufacturer's fuses but results with other manufacturers' fuses of the same class should be similar.
Main program screen with IEEE 1584 Fuse Equation mode selected.
Study has shown that in some cases a shortcut can be taken in analysis of the incident energy on equipment protected by upstream circuit breakers. AFA V3.2 contains the shortcut allowing a calculation of incident energy if the potential arc current falls in the instantaneous trip range of the circuit breaker. Equations have been developed for systems using low-voltage circuit breakers that will output values for incident energy and flash-protection boundary when the available bolted fault current is known or can be calculated. These equations do not require availability of the time-current curves for the circuit breaker.
Main program screen with IEEE 1584 LV Circuit Breakers mode selected.
Benefits:
Related Information:Calculation Example using Empirical ModelCalculation Example using Fuse Equations Calculation Example using Circuit Breakers
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