Utility transformer

[The electron man]

Is the utility transformer fused ?

Like what would happen if you have a phase to phase short before the main ocpd would it just blow up the transformer?

 

[Elect117]

It depends and sometimes.

 

[MD Automation]

It's very common to have POCO transformers protected by "expulsion" fuses.

They can be replaced and reset from the ground using a "hot stick".

Here is the one for my house, showing what happens when an internal fault in the transformers trips that fuse...

 

[busman]

It's very common to have POCO transformers protected by "expulsion" fuses.

They can be replaced and reset from the ground using a "hot stick".

Here is the one for my house, showing what happens when an internal fault in the transformers trips that fuse...

View attachment 2573754

Correct. The "door" of the cutout can be lowered with a hot-stick and re-fused. The "horns" on the top of the cutout are for a "load buster" device to extinguish an arc from opening the door under load. The cutout should be mounted "angled down" so the door wants to fall open with the expulsion mechnism.

Mark

 

[don_resqcapt19]

At a fire scene, I watched as about 25' of 4" RMC with four 500 kcmil copper conductors pretty much vaporized. It was fed by a 750 kva transformer in a vault. When the utility guy got on scene, he opened the vault but the secondary conductors were smoking a lot. He went to the substation, dumped the 12.8 kV feeder circuit, came back and cut the faulted secondary conductors loose and went to the substation and re-energized the circuit to supply power to the customers served by that transformer.

 

[hillbilly1]

Pad mount’s usually have fuses.

 

[Elect117]

Pad mount’s usually have fuses.

Not as common as you might think.

1000kVA usually doesn't. Depending on the primary voltage, 750kVAs might not either. It depends on the primary FLA.

Some utilities fuse the primary at the riser instead.

Transformers may or may not be protected by them. They could be to protect the line from tripping. on a GF at the customer. They usually are not going to provide overload protection. They are also typically higher on the trip curve than the conductor. Depends on the transformer size and if it feeds multiple people.