At what incident energy level would energized electrical work be prohibited?
The answer to your question is not quite as black and white as we would like to think. The prohibition against energized work above a specific incident energy level would most likely come from an employers policy and that policy should be based on thorough risk assessments and documented justification for performing the energized work. I doubt that you will find a standard or regulation that will specifically define that threshold. That being said, it is a commonly held belief that above 40 cal cm/2 the arc blast becomes an as great or greater hazard than the thermal energy and arc rated PPE does not address that factor, thus some policies delineate at that level. The greater emphasis should be to create an electrically safe condition and eliminate the hazard.
Steve you provided a very thoughtful and factual answer to a very difficult question.
Have a Merry Christmas Steve.
That can be answered in two parts:
1. All work should be done de-energized but there a few exceptions per 70E.
Reality is is it done quite often
2. Energized work can be done when using proper PPE. I have heard there are up 120cal suites. As Steve mentioned there is an arc blast issue that has barely been studied.
There should also be a hot work permit issued so management is aware of the dangers the employee is exposed to.
The decision to allow or perform energized electrical work should not be based solely on incident energy. Working on an energized panel with an incident energy of 0.1 cal/cm2 at 18" and a system voltage of 480 VAC still presents a very real shock risk. 70E goes to great lengths to try to prevent energized work by allowing only 2 exceptions covered in 130.2(A). Allowing energized work is a gamble with a life and should not be allowed. Christopher Coache address this very issue in his blog post from November 22, 2017.
Retrieving data ...