AF0100 Arc-Flash Relay
GENERATOR APPLICATION GUIDE
4
Littelfuse.com/ArcFlash
© 2017 Littelfuse Products
NEC
®
ARTICLE 240.87 (2017)
Arc-Energy Reduction
Where the highest continuous current trip setting for which the actual overcurrent device installed in a circuit
breaker is rated or can be adjusted is 1200 A or higher, 240.87(A) and (B) shall apply.
(A) Documentation.
Documentation shall be available to those authorized to design, install, operate, or
inspect the installations as to the location of the circuit breaker(s).
(B) Method to Reduce Clearing Time.
One of the following means shall be provided:
1) Zone-selective interlocking
2) Differential relaying
3) Energy-reducing maintenance switching with local status indicator
4) Energy-reducing active arc-flash mitigation system
5) An instantaneous trip setting that is less than the available arcing current
6) An instantaneous override that is less than the available arcing current
7) An approved equivalent means
ANSI Z10 : RISK CONTROL HIERARCHY
While PPE is often the most talked-about aspect of arc-flash risk mitigation, it is also the least effective means
of doing so. Work and research has been and is being carried out in the engineering controls area particularly to
better mitigate arc-flash risk.
ANSI / AIHA Z10 (OHS Management Standard) hierarchy, from most effective risk mitigation to least, is as follows:
1)
Elimination
– Difficult to achieve
2)
Substitution
– Insulated bus, smaller transformers, arc-resistant gear, current-limiting fuses
3)
Engineering Controls
– Current-limiting devices (fuses, neutral-grounding-resistors), arc-flash relays,
maintenance/instantaneous trip awareness
– Labels, training, use of qualified persons
4)
Administrative Controls
– No work on energized equipment, lockout-tagout
5)
PPE
