Hello,

I have a concern about using an ABB REA 101 AF relay in a SKM study I am performing. The relay is installed in MV switchgear and wired to trip a MV breaker that feeds a transformer to a LV SWGR lineup. When performing the arc flash study, the bus ahead of the LV main breaker, it shows the feed to the breaker as being protected by the REA relay. (I have the REA relay modeled just as an instantaneous OC relay.)

I am concerned that in the event of a real fault on that LV bus, the fiber optic lines in the MV SWGR won't see a flash event in the LV SWGR in another room. I am wondering if I should ignore the REA relay in this simulation or not and if it is actually protecting the feed to the LV main breaker.