NFPA 70E 130.5(G) Incident Energy Analysis Method requires that “The incident energy analysis shall be updated when changes occur in the electrical distribution system that could affect the results of the analysis. The incident energy analysis shall also be reviewed for accuracy at intervals not to exceed 5 years.� One such change could be the available fault current from the electric utility.

Have you seen utility fault current change significantly at a site location?
Yes
No
Depends on the site
Never re-checked utility data

*Significantly - 5 to 10% or more

Yes. Loss of a transmission source due to weather or maintenance. Loss of a feeder. Loss of a substation for rebuild, or maintenance. Load can be picked by an adjacent substation (longer feeders to a different impedance substation transformer) or by a mobile substation (high impedance). Sometimes multiple issues as distribution and transmission work are done simultaneously during the summer construction season. The mission always is to keep the lights on or to restore power as soon as possible.