LV Transformer arc flash labeling
LV Transformer arc flash labeling
(OP)
Using SKM Powertools for arc flash studies and labeling, I've been wondering if there is a better way to handle LV transformers where there are multiple buses in a single enclosure. I usually print separate labels for each bus, which was the suggestion of SKM's technical support. It bothers me to have multiple labels because it is somewhat open to interpretation by potential workers which bus is being worked on. I would feel more comfortable with a single "worst case" label for such equipment. SKM can print labels with line-side and bus data for main-breaker equipment, but I haven't found a way to do this for transformers. Just wondering how others have handled this.
Alan
“The engineer's first problem in any design situation is to discover what the problem really is.” Unk.






RE: LV Transformer arc flash labeling
I will label the main breaker with the AFH there and then a label for the other part of the swgr/swbd which is on the line side of the breaker. There would be two labels then.
RE: LV Transformer arc flash labeling
Thanks for the response. Actually this is a low-voltage dry-type transformer with the primary and secondary terminals in the same enclosure. Primary and secondary overcurrent protective devices are located remotely.
Alan
“The engineer's first problem in any design situation is to discover what the problem really is.” Unk.
RE: LV Transformer arc flash labeling
RE: LV Transformer arc flash labeling
RE: LV Transformer arc flash labeling
The labels include bus voltage to warn of shock hazard and required glove class. I would want this to show the high-side voltage. I suppose I could use the custom table by entering the high side voltage and manipulating the fault current and arc duration to obtain the incident energy value it calculates for the worst case (low-side) terminals.
Considering the number of transformers on some of my projects, that is more manual manipulation than I was hoping to have to do. This gets especially messy when we have multiple system scenarios to evaluate. But the only alternative I see is to create completely custom labels for each transformer.
In the past I've just printed two labels, but I don't like that approach. I was hoping someone else had come up with a solution for what seems like a very common situation.
Thanks,
Alan
“The engineer's first problem in any design situation is to discover what the problem really is.” Unk.
RE: LV Transformer arc flash labeling
RE: LV Transformer arc flash labeling
Alan
“The engineer's first problem in any design situation is to discover what the problem really is.” Unk.
RE: LV Transformer arc flash labeling
RE: LV Transformer arc flash labeling
I'd find the worst case for each terminal compartment. The object of arc flash labeling is to warn workers of the worst possible case they are likely to encounter when working in the area. If there are multiple busses in one compartment, even though the work might be confined to one of them, there's a possibility that an arc could involve any other in the area.
Like working on the primary terminals and dropping the wrench across the secondaries.
RE: LV Transformer arc flash labeling
My original question was how to make the SKM software create these worst case labels somewhat automatically. I have systems with a lot of these transformers and would prefer not to do the calculations manually for every one.
Alan
“The engineer's first problem in any design situation is to discover what the problem really is.” Unk.
RE: LV Transformer arc flash labeling
I model the transformer with a bus at the primary and a bus at the secondary (i.e. TR-1-P and TR-1-S).
I then run the arc flash and these two locations will be together and easy to compare which is the worst case.
When I print the labels I only print the case with the worst AFIE.
RE: LV Transformer arc flash labeling
RE: LV Transformer arc flash labeling
The best method I've found so far is:
1. Run the calculations normally, with buses assigned at the primary and secondary terminals.
2. Create a custom label table.
3. Manually create a table entry for the transformer.
4. Enter the high-side voltage.
5. Enter bolted fault current for the terminals with the worst-case incident energy from the original calculations.
6. Enter a total arcing time and then adjust it up or down as needed in order for the incident energy it calculates to match the worst-case from the original calculations (this is an iterative process).
7. Repeat 3-6 for each transformer.
Alan
“The engineer's first problem in any design situation is to discover what the problem really is.” Unk.
RE: LV Transformer arc flash labeling