The first edition of IEEE 1584 was based on two electrode configurations: referred to as box configuration (enclosure) and an open configuration (in air). Electrode configurationĪnother important variable is the electrode configuration. For the 480V panelboard example, 18 inches is used. However, the specific task must also be considered when defining this distance. IEEE 1584 lists “typical” working distances of 18 inches for low-voltage equipment such as panels and motor control centers, 24 inches for low-voltage switchgear and 36 inches for medium-voltage equipment. Incident energy varies exponentially with the inverse of the distance, the greater the distance, the less incident energy and vice versa. IEEE 1584 defines the working distance as the distance between the potential arc source and the face and chest of the worker. Part 4 concluded that the device for this example will operate in 1 electrical cycle, or 0.167 seconds. The arc duration defines the total exposure by evaluating the time current characteristic of the protective device that is expected to operate and clear the arc flash. The arcing fault current was addressed in part 2. Two important variables are the arcing fault current and the arc duration. IEEE 1584-IEEE Guide for Performing Arc Flash Hazard Calculations defines incident energy as, “The amount of thermal energy impressed on a surface, a certain distance from the source, generated during an electric arc event.” It can be used to determine the arc rating of protective clothing and equipment as part of an arc flash risk assessment. The final part of this series examines incident energy and arc flash boundary calculations for the 480V panelboard example used in this series.
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