Forensic Analysis – Failed Transformer

[GoldenstateEE]

Hi all,
We recently had a failure of a dry-type indoor transformer and are exploring options for forensic analysis to better understand the failure mechanism.
Looking for recommendations on firms or labs that can support this type of work (teardown, material/microscopic analysis, failure determination, etc.).
Any suggestions or past experience would be appreciated. Thank you in advance.

 

[zbang]

What are the indications of failure - open winding, internal short, burned terminal, the magic smoke came out? That'll drive the failure analysis.

 

[GoldenstateEE]

 

[GoldenstateEE]

 

[rambojoe]

Thats easy...
So what ocd tripped? Primary or secondary? Or did the whole neighborhood lose power?
What is primary/secondary voltage?
And who was the last idiot who fired it up?
Clearly human caused.
Looks like medium volt from here..

 

[DBill64]

It looks like it may have experienced some overheating!

 

[jim dungar]

We used to send ours back to the manufacturer. Most are pretty interested in preventing future failures

How long has this been in service?

 

[GoldenstateEE]

Primary 12kV fuses blew. Upstream relay did not trip. Primary is 12.47kV and secondary is 480V. Transformer was energized when it caught on fire.

 

[GoldenstateEE]

We used to send ours back to the manufacturer. Most are pretty interested in preventing future failures

How long has this been in service?

29 years

 

[tortuga]

Probably that little fan in the bottom of the photo failed

 

[GoldenstateEE]

We used to send ours back to the manufacturer. Most are pretty interested in preventing future failures

How long has this been in service?

Jim, I have worked with you at Eaton. You worked at Eaton or Schneider? Frank Waterer used to perform these kind of analysis there.

 

[rambojoe]

Probably that little fan in the bottom of the photo failed

Or the tie wire...
Or the wrench left in there 30y ago and finally fell..

 

[GoldenstateEE]

Or the tie wire...
Or the wrench left in there 30y ago and finally fell..

 

[jim dungar]

Jim, I have worked with you at Eaton. You worked at Eaton or Schneider? Frank Waterer used to perform these kind of analysis there.

I was at Schneider.

What does the center coil look like? I can't see much more than the fire damage.
What type of protective relay, does it save history?

Did you have critters nesting in there? What does the bottom of the enclosure look like.

 

[tortuga]

Any change in load recently? Is it a 480/277 or 480 delta?

 

[Joe.B]

https://www.atf.gov/laboratories/fire-research-laboratory

 

[zbang]

Any lightning in the area when it happened? A strike on or close to the primary lines could do it.

 

[TwoBlocked]

I'm betting on failed insulation causing a shorted coil, drawing excessive current in that area, producing heat beyond the insulation rating, causing more shorted coils and so on. This can be caught with a differential relay and is regularly used on large oil filled transformers, but not on dry type.

 

[jim dungar]

This can be caught with a differential relay and is regularly used on large oil filled transformers, but not on dry type.

The keyword here is "large". Dry type transformers are not usually rated in MVA.

Evidently there was a protective relay, but it didn't operate before the fuses.