The key changes to IEEE-1584-2018.
The IEEE-1584 standard is used to calculate the incident energy level, or the heat released during an arc flash explosion. This standard appeared in 2002 and is based on statistics, physics and empirical formulae to accurately estimate the heat to which a person could be exposed if situated 18 inches from the electric arc.
In the new version of the standard, IEEE-1584-2018, arc flash experimental testing showed that the heat given off 18 inches from the panel could also vary with electrode configuration, box size and spacing of fixed conductors. These three new parameters change the trajectory of the arc flash and make it possible to evaluate the incident energy level with more precision. In the old version of the standard, these parameters where estimated using a linear formula, whereas in the new standard it is an empirical formula that fits the experimental data with the most precision.
- VCB (vertical conductors, electrodes inside a metal « box » enclosure) ≡ the conductors are oriented vertically, and the electrodes point downwards inside a metal box.
This configuration directs the arc flash towards the bottom of the panel and it is then redirected towards the front of the panel.
- HCB (Horizontal conductors, electrodes inside a metal « box » enclosure) ≡ the conductors are oriented horizontally, and electrodes point frontwards inside a metal box.
This configuration directs the arc flash directly in front of the electrical panel.
- VCBB (Vertical conductors, electrodes terminated in an isolating barrier inside a metal « box » enclosure) ≡ conductors are oriented vertically, the electrode terminal is insulated and inside the box.
This configuration directs the arc flash in front of the electrical panel, but there could be a certain distance between the bus and the insulated component, which increases the safety perimeter when compared to the HCB configuration.
- HOA (Horizontal conductors electrodes in open air) ≡ the conductors are oriented horizontally in open air.
This configuration directs the arc flash in front of the electrodes, but in a less concentrated fashion than in the HCB configuration.
- VOA (Vertical conductors electrodes in open air) ≡ the conductors are oriented vertically in open air.
This configuration directs the arc flash directly towards the ground.
The electrode configuration allows us to estimate the incident energy level in front of the panel with more precision. Below is the variation in incident energy levels according to electrode configuration. They are ordered from highest to lowest energy levels:
The size of the electrical box:
The size of the box (width, height and depth) changes the direction and concentration of the arc flash. An increase in box size (width X height) leads to a decrease in the incident energy level 18 inches from the panel. However, a decrease in box depth leads to a decrease of the incident energy at 18 inches from the panel.
Spacing between conductors:
A decrease in the distance between electrodes leads to an increase in the arc flash current. However, on higher voltages, the arc current will be less affected by the distance between electrodes. The current always follows the easiest path to close the circuit, so if the distance between conductors is high, the arc’s current can travel through a non-linear path and cause an increase in the heat given off 18 inches from the panel.
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