Hello everyone. I am currently performing an arc flash study and I am some confused with modeling for the switchgear installed on the facility that I am working at.

I have attached some photos of the equipment that I need to analyze both switchgear and main breaker. Upwards of the swithgear there is the transformer and it is protected by primary fuses.

So I think there is a very important point regarding the switchgear, although the main breaker seems to be enclosed, when it was opened, I realized that the main breaker was not insulated from the line side and distribution bus.


First, do I need to consider the switchgear as open bus? or I need to take only dimensions of the front side of the main breaker (because technically the main breaker it is not inside a box, unless the switchgear as a whole is considered as a big box)?

Second, according to Annex C of the 1584 standard, I need to calculate the incident energy for the bus as if the main breaker failed if it had a stud connection problem with the VCBB electrodes type, and type VCB if the breaker presented an internal failure so, it could not open.

My point of view is the following.

I understand that in both cases the arcing time will be calculated based on the total melting time from the primary fuses of the transformer for both cases aforementioned (because the main breaker of the switchgear already failed).

Then if I am analyzing the case when the main breaker can trip the arcing current (arcing occurring in the distribution bus) the model applied for the analysis will be VCCB according to the same ANNEX C.

So do I need to analyze the switchgear with 2 incident energy results? One for the main section and the second for the distribution section?



What do you think?
Thank you,

I would treat the switchboard as one large enclosure, basing the incident energy on the line side of the main breaker.

Being within an enclosure can focus the arc flash energy forward toward the worker. I would consider the breaker within an enclosure, (and as previous response said, consider the exposure of the line side bus upstream of the main breaker for the entire switchboard unless there is an arc rated barrier partitioning off some part of it).

Many electricians and mechanics make the error in referring to a switchboard as "switchgear". However, take a look at the name plate on the gear, that ought to tell you. I'd bet this is a Square D I-Line switchboard.

First: I will definitely calculate the AFIE at the line side of the main breaker and apply it for the whole equipment. You should only consider the AFIE at the load side of the main when there is proper SEGREGATION between the incoming section and the adjacent feeder compartments. This according to IEEE 1584.1 2013. Additionally, proper segregation is not something we can evaluate just by looking at the equipment. Metal enclosed equipment that satisfies the tests of IEEE C37.20.7 Suffix C is basically the only means of making sure you have proper SEGREGATION. If your equipment has been tested according to this standard, then I would include a label for the incoming section and another for the rest of the feeders.

Second: If you are doing the AFHA using the IEEE 1584 2018 standard, you need to figure out the enclosure size. I will consider the whole enclosure side for the line side AFIE as mentioned before in this thread.

Third: If you are doing the AFHA using the IEEE 1584 2018 standard the configuration (VCB, VCBB, etc.) is now a required input. If I would have to choose an electroduct configuration with the information I saw, I would choose an HCB,