I have got very high incident energy/high category on the secondary of the transformer, normally shown as line side of main breaker on the secondary of the transformer. Do you think we have to put the dangerous/ cate 4 label on this portion or we can just put lower category label on the load side? Thanks!

You'll probably want to provide more detail with your question.

In my experience, the main factor in deciding what incident energy you see at the transformer secondary is the clearing time of the upstream protective device. I generally see extreme danger IE levels at transformer secondarys.

I have a control cabinet fed from a 225kVA auto-transformer. The 2ndary voltage is 460V. Inside cabinet I have a main breaker and some sub-breakers. The load side of main breaker is only 0 level. But the line side is rated at dangerous according to my PTW32 model. So do you think I have to put dangerous lable on this cabinet? The breakers are all in one cabinet without isolation. Any solution if I want to put 0 label on the cabinet?

I have a control cabinet fed from a 225kVA auto-transformer. The 2ndary voltage is 460V. Inside cabinet I have a main breaker and some sub-breakers. The load side of main breaker is only 0 level. But the line side is rated at dangerous according to my PTW32 model. So do you think I have to put dangerous lable on this cabinet? The breakers are all in one cabinet without isolation. Any solution if I want to put 0 label on the cabinet? Thanks!

In a case where you've got no isolation and all the things you mentioned are in the same panel, there is no way around putting a 4 on the cabinet. This is a common problem with arc flash because it is impractical to put on a level 4 PPE suit to work in any panel that has mains, yet that is what the book says to do..

Thanks Deprico, could you kindly show me where I can find those description? In NFPA 70E or IEEE 1584? I just want to make sure of this.

Please reference the IEEE-1584 document.