lielec11
Senior Member
- Location
- Charlotte, NC
I am working on a power system study for a client. It is all 120/208V, 3-phase normal distribution with three gensets paralleled together on the emergency side. I ran two scenarios, one for normal power and one for emergency operation. Client came back requesting I do a closed transition scenario because the ATS have the ability to do that.
Question I have came up during the arc flash analysis. Under the closed transition scenario a few buses jumped up in arcing fault. This makes sense to me as we now have contributions from both the normal and emergency side of the ATS. However, the "protective device arcing fault" dropped lower. Low enough to a point where the equipment should not be worked on live based on the incident energy levels.
I can't seem to understand why the protective device arcing fault is lower for the closed transition scenario than in both the normal and emergency scenario. The protective device that will clear the fault is on the normal side and is located in an upstream DP but in both the normal and emergency cases the bus arcing fault always was equal to the "protective device arcing fault". I did a search and can't seem to find out exactly what this is or how to calculate it. I couldn't find anything in IEEE 1584 either.
Thoughts?
Question I have came up during the arc flash analysis. Under the closed transition scenario a few buses jumped up in arcing fault. This makes sense to me as we now have contributions from both the normal and emergency side of the ATS. However, the "protective device arcing fault" dropped lower. Low enough to a point where the equipment should not be worked on live based on the incident energy levels.
I can't seem to understand why the protective device arcing fault is lower for the closed transition scenario than in both the normal and emergency scenario. The protective device that will clear the fault is on the normal side and is located in an upstream DP but in both the normal and emergency cases the bus arcing fault always was equal to the "protective device arcing fault". I did a search and can't seem to find out exactly what this is or how to calculate it. I couldn't find anything in IEEE 1584 either.
Thoughts?