ArcFlash 2 (30) Flashcards
What is 1584.1?
Guide for specifying performance of an arc-flash study.
How does 1584.1 treat the question of how many cases to study?
Engineering judgment.
Does 1584.1 have content that affects our calculation?
Not really.
What voltage range does 1584 cover?
208V - 15 kV
How does 1584 treat single-phase and DC?
They’re not included.
What does 1584 mean by a ‘one-bus-away run’?
We need current through the first upstream device, not total fault current at a point.
What if we have only the melting time and not clearing time for fuses?
1584 gives percentages to add.
What about time for relay instantaneous operation and breaker clearing time?
1584 says you have to add them.
What is the flash-protection boundary?
Distance at which a second degree burn could occur.
Do I need to remember anything about the arc-flash boundary equation?
Not really. It’s partly empirically based. Just put in the right numbers.
The flash-protection boundary is based on what incident energy?
5.0 J/cm2
What is 5 J/cm2 in cal/cm2?
1.2 cal/cm2
Describe the 1584 equation for calculating arc-fault magnitudes.
Complex logarithnic equation with several terms.
What two values of arc-fault are required?
100% and 85% (for slower clearing time)
What is the first step in determining incident energy?
For the calculated arc-fault, the incident energy for ‘normalized’ time and distance.
What is the ‘normalized’ time and distance?
Clearing time of 0.2 seconds and a distance to the person of 610 mm.
What is the second step in determining the incident energy?
Adjusting the normalized energy to the actual clearing time and distance.
What are the methods available for determining arc-flash levels?
NFPA 70E table, theoretical (Lee) method, 1584
What effect does arc-time have on incident energy?
Linear
What effect does distance from the arc have?
Inverse exponential affect, with the exponent depending on the enclosure size.
What effect does X/R ratio, frequency, and electrode material have?
Little or no effect on arc current and incident energy, so they are neglected.
How much impact does bus spacing have?
Incident energy depends primarily on calculated arc current. Bus gap is a small factor.
How does 1584 characterize grounding?
Solid or ungrounded (everything else but solid).
What kind of fault is 1584 based on?
3-phase. These produce the greatest energy, and anything less quickly escalates to 3-phase anyway.
What is the 2 second rule?
It allows assuming a 2-sec max clearing on the basis that a person will move away quickly.
In ETAP, what is the ‘X Factor’?
The is the exponent to be used in determining the effect of distance.
What is the Limited Approach Boundary?
The distance from an exposed energized circuit part within which a shock hazard exists.
Is LAB related directly to arc-flash?
Not that I can tell.
What are the two options for ETAP arc-flash analysis?
Quick (local) and Global.
How do deal with the 85% arcing current cases in ETAP?
ETAP runs the analysis with both values, and reports the worst one.
