Arc Flash Evaluation - Generator Camlock

[PE (always learning)]

Hey everyone,

I’m doing a power systems study for an existing building that has a 2000 amp switchboard for connecting a generator in the event that the power goes out. The generator switchboard feeds the main distribution panel and both the generator switchboard main and the normal power main breaker have a key interlock. There are no critical or life safety systems, but I have set the generator switchboard breaker to coordinate with the down stream breakers in the main distribution panel. My question is, do I need to provide an arc flash label for the generator switchboard even though there is currently no generator hooked up at the moment? Also, I don’t even know what KW generator they would provide in the event that they would use emergency power. I could try and assume a worst case, but that would require several different studies and it would also effect my downstream panels. Anyone who has come across a situation like this, what did you assume for your study?

 

[jim dungar]

I seem to recall doing something like this. In that case we labeled the generator breaker based on the main bus of the switchboard (basically its loadside lugs). The customer's Energized Work Permits covers the PPE selection procedure for working when connected to generator power.

If I guess at which generator may be used, I might as well save time and just guess at the AF results.

 

[petersonra]

Hey everyone,

I’m doing a power systems study for an existing building that has a 2000 amp switchboard for connecting a generator in the event that the power goes out. The generator switchboard feeds the main distribution panel and both the generator switchboard main and the normal power main breaker have a key interlock. There are no critical or life safety systems, but I have set the generator switchboard breaker to coordinate with the down stream breakers in the main distribution panel. My question is, do I need to provide an arc flash label for the generator switchboard even though there is currently no generator hooked up at the moment? Also, I don’t even know what KW generator they would provide in the event that they would use emergency power. I could try and assume a worst case, but that would require several different studies and it would also effect my downstream panels. Anyone who has come across a situation like this, what did you assume for your study?

I don't see how you could provide a label unless you know what generator is going to be used.

 

[wbdvt]

Since the generator circuit is only energized when a generator is attached, one needs to know the generator parameters to be able to calculate the incident energy. You could make some reasonable assumptions on the generator size based on the conductor size and load or just label the generator connected equipment with something that says not analyzed, depends on generator size, do not work energized. Some places have a no work policy when the system is on generator power.