Short Circuit Study

[DMG_1]

I am doing a short circuit study at a location that has multiple 13.8 kV and 4.16 kV transformers on the primary side. In the transformer model I have been putting in Cooper ELSP fuses (current limiting) and Bay-O-Net fuses (overload) in series on the primary side. For the short circuit study the Bay-O-Net fuses are coming up as failing on short circuit current. I know that the ELSP fuses serves to protect the transformer from severe internal faults but also thought that since it is current limiting that it would protect the Bay-O-Net fuse from excessive short circuit currents. Any ideas on this?

Thanks,
Dave

 

[ron]

For one to protect the other, there would have to be a series rating between them.

 

[steve66]

For one to protect the other, there would have to be a series rating between them.

Ron:

I'd normally agree, but that seems to be the intended installation method even if the fuses aren't specifically series rated, per this document (see the 2nd paragraph under APPLICATION);

http://www.cooperindustries.com/con...s/resources/library/240_Fusing/CA132011EN.pdf

Edit: I take that back. Now that I look at it again, it looks like they are specifically recommending the ELSP fuses for backup protection. I assume those would be series rated.

What are you using to do the short circuit study? Most software only checks the available fault current and compares it to the rating of the fuse.