3/10/2024 0 Comments Arc flash boundary definition![]() ![]() The time-current curves included with the replacement trip unit may, or may not, include the circuit breaker operating time. Note that some low-voltage power circuit breakers may be equipped with retrofit trip units. If the total clearing time at the arcing fault current is less than 0.01 s, then 0.01 s may be used for the time.įor low-voltage circuit breakers with integral trip units, the manufacturer's time-current curves include both the device tripping time and clearing time in most cases. If the curve only consists of the average melt time, ten percent of time plus an additional 0.004 s should be added, to determine the total clearing time. For fuses, the manufacturer's time-current curves may include both melting and clearing time. ![]() Use protective device characteristics, which can be found in manufacturer's data. HOA - Horizontal electrodes in open air.HCB - Horizontal electrodes in a metal box. ![]() VCCB - Vertical electrodes terminated in an insulating barrier in a metal box.VCB - Vertical electrodes in a metal box/enclosure.IEEE 1584 - 2018 model features five different electrode/bus configurations as illustrated below: Tests were also conducted in open air and included the original vertical configuration in open air and a new configuration with the electrodes oriented horizontally. Research has also indicated that if vertical electrodes are terminated into an insulating the arc hits the barrier and the plasma cloud is directed more towards the enclosure opening. When the electrodes are placed horizontally, the arc plasma is directed from the ends of the electrodes outward. As a result, the IEEE 1584 - 2018 project team conducted many tests using electrode orientations that include both a horizontal configuration and vertical electrodes that terminate into an insulating barrier. Research has shown that incident energy can be influenced by the electrode orientation. ![]()
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