Fuse Protection of Power Transformers

Status
Not open for further replies.
5-60MVA is quite a spread.
even our 10 MVA mobile is relay protected
the old 5 MVA mobile isn’t.


No personnel protection when working in station. (Hot line tag group settings)
no differential
no low oil trip
no 50
no UF of OF (ok so not a big deal, but still)
no OV or UV
no thermal protection
no sudden pressure..
no 21

ill admit, a couple of these will trip only after the damage is done (87 & 63), but it may not be catastrophic with quicker response times of a relay vs fuse.
 
In other words catastrophic vs none catastrophic failure.

Correct if I'm wrong: turn to turn fault does not blow the fuse (?). Oil heats up and the unit catches fire. 87 on the other hand trips it before fire. Right?:unsure:
 
Hopefully...;)

BUT!, a trip before the fire will be WAY less costly as far as cleanup time and return to service.

real life situation...
someone decided to see what would happen if they shot a round or two in a substation... hit one of the transformer fins.
transformer tripped on low oil in the middle of the night. Crew got there and immediately thought the worse until they discovered the bullet hole. TTR testing, looking at and examining all equipment, and bringing in and setting up the mobile took about all night to get the station going again, but the crew was able to shut the valve off on the damaged set of fins and repair In place.(welded the holes). Aggravating? Yes. almost Two weeks of worry and work, but the transformer was saved and didn’t have to be replaced.

fuses wouldn’t have done that...
 
What would have happened in the fuse case? I mean I have an idea... But curious to what extent the unit would have to be rebuilt.
 
Last edited:
mbrooke said:
What would have happened in the fuse case? I mean I have an idea... But curious to what extent the unit would have to be rebuilt.
Click to expand...
Rebuilt??
im just talking about cleaning up the mess after a catastrophic failure.
rebuilding isn’t an option...

at some point it’s about containment and saving the surrounding equipment. The transformers gone. No need to take out the entire sub with it.
 
Hv&Lv said:
Rebuilt??
im just talking about cleaning up the mess after a catastrophic failure.
rebuilding isn’t an option...

at some point it’s about containment and saving the surrounding equipment. The transformers gone. No need to take out the entire sub with it.
Click to expand...


That bad if the oil leaked out in a fuse protected unit?
 
Oh! I misunderstood...
what would have happened in the case of the oil draining with the fuses rather than low oil relay...

let’s think about this a minute... no insulating oil on a 115kv bushing inside a transformer.
we just lowered the dielectric constant from ~2 to ~1.

we also lost our cooling medium, temps going up in the core..

fuses are waiting on an overcurrent to blow, which is coming soon...
 
Don’t think so...
I see the resulting arc inside the unit burning everything and ruining the coil. Once that’s done, it’s over.
 
Probably cheaper to scrap the unit and start over.
shipping, disassembly and reassembly, testing and checking everything out..
that’s IF it can be done. I don’t ever think I’ve seen a refurbished power transformer. That’s not to say it isn’t done, as I haven’t seen them all.
We did buy an old Waukesha unit some years back, but it was taken out of service and replaced with a larger unit at its original location before we bought it.
it didn’t open on a fault.
 
You make a good point here.

Though, can one argue an occasional scrapped unit is cheaper than fuses implemented across multiple substations. Fuses save lots on batteries, wiring, control huts, maintenance, ect.
 
Status
Not open for further replies.
Top