Largest sealed Dry Type you can get?

[majesus]

Hello,

I am looking for an outdoor rated 2.5MVA stepdown XFMR from 4kV to 600V. This is going at a mine site in the North and the environment is dusty. I am trying to avoid oil type XFMRS if I can. It's a not a big deal, but I am curious, what's the largest dry type I can get that is "sealed" from the outside environment? Transformers need to disapate heat, but I was wondering does a 2.5MVA dry type with no vents exist on the market?

Secondly, does anyone have a hard copy of "What we need to know about dry-type transformers" from Electrical Apparatus Magazine, Oct 2002 by Nailen, Richard L?

There is an online version, but the figures are missing. Can someone please scan the article? It's a good read.

http://findarticles.com/p/articles/mi_qa3726/is_200210/ai_n9132856/?tag=content;col1

Thanks
Majesus

 

[juleselec]

Yes, ABB cast-resin dry type transformers go up to 40MVA.

 

[Zogzog]

We stock 2.5MVA cast coils, can build them up to 10MVA. So you should not have a problem finding one.

 

[majesus]

Cool. Thanks guys for the help.
Cast coils is the key ;o)
Cheers,
Majesus

 

[ScottyUK]

Beware of PD problems on bigger dry types. A lot of people can build dry transformers. The number who can build them well is somewhat smaller.


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If we learn from our mistakes I'm getting a great education!

 

[Zogzog]

Good point Scotty, PD testing at the factory of each HV coil is important. Not batch testing, every coil.

 

[dpc]

The typical cast-coil transformer is not "sealed" from the environment. The windings are well-protected and could be considered sealed, but the enclosure is vented. Unless you want to go with some exotic water-cooled option, there will be openings to the outside world.

I would have no problem using these outside, but dirt and dust will still get inside the enclosure, just like any other dry-type.



David Castor

http://www.cvoes.com

 

[Hoxton]

Where is "the North"?

If you do not want a mineral oil cooled unit, then have you considered MIDEL? This is a non flammable biodegradable liquid. Here in UK it is available and quite useful, given the increasing views on the environment and safety aspects. I am not sure if this is availabe or acceptable in all countries.

 

[DTR2011]

Cooper Power and ABB have similar fluids.

Interesting note... I did some work on an ABB unit with the BIOTEMP fluid about a month ago at a wind farm in South Dakota. The unit was not yet energized. The "oil" was frozen solid. Per ABB, it was deemed safe to energize the unit with full thermal and dielectric properties.

 

[ScottyUK]

Hoxton - Where is "the North"?

Newcastle and the bits further up. As distinct from Gateshead, which is clearly in "the South".


----------------------------------

If we learn from our mistakes I'm getting a great education!

 

[majesus]

Transformer shall be located in North Canada.

We have the same type of biodegradable oil. For example, Cooper offers a product called FM3

http://www.cooperpower.com/products/dielectric/envirotempFR3/

It's not flammable, but fire resistant. Midel is also fire resistant. It sill is flammable just at a high fire point. (>300°C)


DPC, so at 2.5MVA, vents are necessary. I am looking for it all. Dry type with no vents, just wishful thinking.

__________________________________________________________________
Just a note, it's not a big deal to go with oil. I'm just exploring available options. We place an oil containment around the XFMR and move on.

Cheers,
Majesus

 

[ScottyUK]

majesus,

Are you trying to avoid the typically massive Ex 'd' enclosures? Based on the former coal miners I have worked with you probably don't want to give them anything remotely breakable.

Have you considered a sand-filled design which would have better heat rejection to ambient than an air-filled enclosure?


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If we learn from our mistakes I'm getting a great education!

 

[dpc]

If these are outdoor, I'm not sure I see the problem with oil. Mineral oil is not particularly hazardous.



David Castor

http://www.cvoes.com

 

[majesus]

I was just exploring the options of going with a seal dry type to get around oil. That's all. Just product huntin but will go with an oil filled XFMR.


Note: GE and ABB came back this afternoon with details. Largest they can go that is dry type, sealed is 500kVA.

Thanks,
Majesus

 

[Hoxton]

Majesus - sorry for misinformation, i checked with midel, they do certify it as having a high fire point, not as inflammable.

 

[dpc]

I believe you can order back issues here for $5.00:

http://www.eamagazine.com/

David Castor

http://www.cvoes.com

 

[Zogzog]

If you still want to go cast coil I can do that easy. Would put this in a NEMA 3R enclosure and we always add gaskets and filters to our 3R enclosures. Heater strip are also standard. Can add fans, tempature monitors, whatever you need. CU or AL.

All our coil are factory PD tested, then get a PF/DF, TTR, IR , exication test and winding resistance before shipment.

 

[controlsdude]

I know that dry types transformers create ozone which will attract any dust within its area. If you have vents with filters you will either be cleaning the filters often or you will probably have an overheating problem.

 

[CanadianKid]

A Canadian manufacturer, Rex Manufacturing located in the Toronto area does make large resin cast trasformers up to 10 MVA, and they do perform all the standard ANSI tests including PD as part of the full testing regiment. They have been in business for quite a while and so have some decent experience. Suggest you call them and see what they would provide.

 

[TK007]

Search online for Resibloc. These transformers are dry-type, they can go up to 60 MVA and are suitable for temperature down to -60°C. I used some outside in northern Quebec, for mining applications.

-Y