Dry type transformer 3

[ahmadnece]

what is the difference between the dry type transformer and the oil type transformer in medium voltage ?
which is more economicaly and safty ?if any manuals or links serve this issue i'll be so thankfull

 

[alehman]

For indoor applications, oil insulated transformers typically will be required to be installed in a fire-rated vault. For outdoor applications, there is a fire hazard to nearby structures and other transformers. Oil transformers are generally considered more reliable and are most common for outdoor installations.

Dry type transformers are typically less expensive and do not require a vault when installed indoors. The insulation is susceptible to moisture absorption, which reduces reliability particularly for outdoor applications or where the transformer is not energized at all times. Dry transformers are most common for indoor installations.

A variation of the dry type is the encapsulated coil type which reduces the moisture problems, but is significantly more expensive.

A fourth option is non-flammable or 'less'-flammable liquid insulation. This has the reliability advantages of oil insulation, with minimal fire hazard. It can be used indoors without a vault in many cases. It is generally the most expensive of the four types.

 

[jraef]

Nice summary.

 

[Skogsgurra]

There are different types of dry transformers. The cast resin type may have quality problems. Partial discharge in voids between resin and primary winding has resulted in flash-over and total destruction in at least four transformers that I have inspected. That doesn't happen with the "Geafoil" type insulation (the conductors are wound with insulation material instead of being cast in resin).

Gunnar Englund

http://www.gke.org

 

[alehman]

I'm not familiar with Geafoil. Who makes that?

 

[ahmadnece]

thanks for all replies

 

[Skogsgurra]

I think that is was AEG that introduced that technique. They tended to have "GEA" in their trade names (GEAMAT for instance). And I know that Siemens is using it now.



Gunnar Englund

http://www.gke.org

 

[RalphChristie]

Gunnar:

The name is Geafol. I am also not familiar with it, but did a search on google and found this interesting article (first hit):

http://www.chem.unep.ch/pops/pcb_activities/PCB_proceeding/Presentations/Heinz Raithel.pdf

Regards
Ralph



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