Installing a fuse without a fuse block/holder inside an enclosure

[MatthewFaraday]

Hey Guys! This is my first time posting here but this place looks useful. I don't have all of the information yet for this question but I'm just looking for some general ideas.

My job is to reduce the required arc flash PPE levels in six transformers at a facility. What our contractor wants us to do is use both ETAP and PTW to size fuses for the secondary side of these six transformers. The fuses will then reduce the incident energy of the transformers. I found a fuse for five of the transformers and our designers are drawing some sketches up right now. The sixth transformer is giving me problems. I could only find one fuse that would reduce the arc flash levels. Unfortunately, I called the manufacturer of this fuse and they don't have a fuse block for this particular fuse. Does anyone here know how we could install the fuse inside a transformer without a fuse block?

We cannot open up the transformer and look inside because of the arc flash hazard. So we are assuming everything based on industry standards with our drawings. The transformer is a 1000 KVA pad mount transformer.

 

[ScottyUK]

A starting point would be to tell us what fuselink you're considering. Mounting arrangements obviously depend on the fuselink design. ;-)

Have you considered using a differential or REF scheme on the LV winding? Unit protection reduces the arc flash hazard by very fast clearance of in-zone faults. It might work out cheaper than taking your home-made solution to a test house to get it proof-tested for fault withstand.

 

[davidbeach]

Relay based arc flash protection will do far better than fuses. Differential is the best, but low-set instantaneous in a maintenance mode is good too. The problem with fuses is that if the fault current falls below the instantaneous point of the fuse the clearing time can get much longer with only slight reductions in fault current; accompanied by significant increases in arc flash hazard. Routine utility maintenance work can result in meaningful reductions in fault current. Will your fuse still provide the necessary protection?