Oil Filed vs Dry Type Transformer

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philly

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What are some of the advantages/disadvantages of using oil filled vs dry type transformers in an industrial setting?

I have seen several facilities where the dry type transformers are located inside of the electrical room with the rest of the equipment and have seen others where oil filled transformers were located outside of the room with conduit/busduct going to the equipment inside the room.

So is the decision to use oil filled driven by where the transformer will be located (inside vs outside)? Is the decision to locate transformer outside of room usually for saving space within the room? Obviously if you have them both in the room you can "close couple" them which will be a cheaper installation.

With an Oil filled transformer do you need spill containment and fire barriers even if using FR3 fluid?

Just want to hear others take on the two different applications.
 
And if you tend to push things a little, the oil type will hold up much better. I've been told by a POCO lineman that it's nothing to push them 150%;)
 
I generally see dry type for low voltage (600V or under) on both primary and secondary, and oil filled with the primary is 4KV or more.
 
mopowr steve said:
And if you tend to push things a little, the oil type will hold up much better. I've been told by a POCO lineman that it's nothing to push them 150%;)
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That is what Potelco (PSE service contractor) told us at habitat when they dropped in a 25 kVA to supply 5 town house units each with 200 A service. That was 5 years ago, AFAIK, still functioning.
 
In my experience, liquid filled transformers - 1000 kVA and larger - have proven to be more reliable. In smaller sizes, I would tend to use dry.
 
Dry type can be OK indoors, DRY location.

I remember one when I worked for a utility in S. Louisiana, under the dry type xfmr was a pile of corroded core.

RC
 
Fnewman said:
In my experience, liquid filled transformers - 1000 kVA and larger - have proven to be more reliable. In smaller sizes, I would tend to use dry.
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I’ve got to agree with you there. OK oil filled transformers require bunding and we always mounted them on a plinth, a bit of extra work for the civil gang. Some of our transformers were installed in the 30’s. With just an occasional bit of TLC they keep plodding on.

I’ve never had a fire with oil filled, LV dry type several times.
 
Most of ours were 11kV primary. ONAN. Variable speed drive supply transformers for the most part.
Over the 50 years in that field I have seen a few transformer failures. Not a lot it has to be said. Some were dry typle, a fe were cast resin, and only one was ONAN.

Yes they need to be maintained. A change of oil now and again? Check the tightness of the terminals.
 
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