Previous in Forum: Wattmetric protection in main High Voltage supply   Next in Forum: Death by van der Graff generator
Close
Close
Close
8 comments
Active Contributor

Join Date: Jan 2008
Posts: 16

Dry vs Oil Transformers

01/19/2008 3:50 PM

Since dry transformers are more sensible to overheating, It should be more preferable to use oil transformers. But it is always recommended to use dry transformers in closed spaces. Today the oil is not flammable as it was in the past. So why oil transformers are not in wider use in closed places? Is there another reason, and is this reason technical or economical?

Register to Reply
Pathfinder Tags: Dry oil overheating transformers
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.
Associate
Popular Science - Weaponology - New Member Popular Science - Biology - New Member

Join Date: Jan 2008
Location: Haiti
Posts: 52
#1

Re: Dry vs Oil Transformers

01/19/2008 11:25 PM

When oil transformers are overloaded , they heat to ebullition provoking strong explosion from enclosed gases and wide spills of boiling dielectric oil inside the plant endangering Lives. Oil burns are very bad because,like molten plastics or acids one has the normal reflex to wipe out the boiling oil on one hand with the other hand thus burning the helping hand also! Outside its less likely to harm people.

Take note that cities like Monterrey Mexico, the "Comision Federal de Electricidad" (CFE) prefers to use dry transformers on the side walk electrical posts.

Oil transformers are cheaper than dry ones, at least in Mexico.

Issa David Talamas.

__________________
few things are more gratifying than winning a loosing hand
Register to Reply
Power-User

Join Date: Apr 2006
Location: Texas, by God! Houston for precision
Posts: 167
Good Answers: 2
#2

Re: Dry vs Oil Transformers

01/19/2008 11:43 PM

There are still a lot of oil transformers in use (not, rpt not for sale new) which used polychlorinated biphenyls (PCBs), and used ones still show up oin the marketplace. Using the logic of the legal shamans, all oil transformers are carcinogens, and I can get a jury to believe it.

__________________
If all else fails, read the directions. That's if, and only if.
Register to Reply
Power-User

Join Date: Jul 2006
Location: Springfield, Tennessee U.S.A.
Posts: 231
Good Answers: 16
#3

Re: Dry vs Oil Transformers

01/20/2008 12:16 AM

From approximately ten (10) years ago I remember a serious incident that occurred in Nashville, Tennessee U.S.A. when several tourists and downtown workers were near the top of a transformer cover at the moment the transformer exploded. This transformer, like most in the city's downtown area was in a subterranean pit beneath the sidewalk and covered with a steel treadplate. The transformer was oil-filled.

In human terms the cost was tremendous, as one (1) person was killed and three (3) others suffered severe burns over much of their bodies. They did survive after many surgeries, skin grafts, and months of hospitalization and rehabilitation. But what a survival.

The big stink was that state law placed a rather low ceiling on the liability of the electrical utility, in this case Nashville Electric Service (N.E.S.). This state law was upheld by the state courts. N.E.S. was accused of negligence for transformer maintenance and selection of the wrong type of transformer given its typical proximity to people. The oil-filled units were eventually replaced with dry units at a substancial cost.

Regards,

Ing. Robert Forbus

__________________
"Yeah, but will it fit?"
Register to Reply
Active Contributor

Join Date: Sep 2007
Location: RAJAHMUNDRY, ANDHRA PRADESH, INDIA.
Posts: 11
#4

Re: Dry vs Oil Transformers

01/20/2008 12:57 AM

It is always adivceble to use Oil Filled Transformers for Large Capacities and either Dry Type or Oil Filled Transformers Can be used for Small Capacities. For enclosed spaces it is better to use Dry Type Transformers due to ease in Maintenance and no Explosion of Oil in case of Failure of Transformer. Safety should be given priority over Economics.

Register to Reply
Guru

Join Date: Nov 2006
Posts: 720
Good Answers: 2
#5

Re: Dry vs Oil Transformers

01/20/2008 7:53 AM

There are two types of Dry transformers one is a class C dry type and the other a cast resein transformer.Cast resein trans formers are maintenace free though initially expensive.Though now transformers oil is less flammable maintenance on oil transformer cannot be avoided .Oil checking and Filtartion form a part of maintenance.Inspite of precautions like explosion vent etc oil flowcannot be prevented when pressure builds up under certain fault conditions.Cast resein transformers therefore prffered in certain when transformers are installed in basements.Fire spreading to other parts from an oil filled transformer is another hazard particularly in Inddor and basement installations.However large power transformers are still oil filled type only.

__________________
To avoid crticism do nothing,say nothing,be nothing
Register to Reply
Active Contributor

Join Date: Jul 2007
Location: Los Angeles
Posts: 23
#6

Re: Dry vs Oil Transformers

01/20/2008 3:26 PM

I think the reasons Dry type transformers are specified VS oil filled has to do with the

Oil filled PCB filled transformers from years past.This has made everyone afraid of oil. It became an trend to specify Dry and everyone does it that way because thats the way its done. I have heard of issues with Silicon. I have never heard any thing bad about R-Temp. ( I think it has been discontinued)

I want to make a case for oil - these are my thoughts

1) I think most of the horror stories from the other post are mineral oil filled. I believe it is true all these things happened. I don't believe the new Low Fire-point Fluids made by ABB and Cooper Power have these issues.

2) ABB's Bio-temp and Cooper Powers FR3 filled, I believe are the only Low Fire-point fluids available. I know the FR3 filled best and can offer a few important points. I think this applies to both.

They are made from soy beans and are covered under the edible oil regulatory reform act. If the oil spills it makes it easier to clean up

3) Oil filled transformer are more efficient than Dry Type.

4) Oil Filled are Generally smaller

5) They Generally have a Longer Service Life. Cooper Power has data that retro-filling FR3 Oil can actually increase the service life

6) Oil filled transformers are easier to test. A simple DGA oil analysis can be performed regularly to help predict failure. A dry type transformer has to be de-energized to perform any kind of testing

7) These fluids have a flawless safety record-- I am told

8) The transformers can be UL and Factory Mutual Listed

9) Substation transformers can be purchased with they're own Oil Containment

10) Oil Filled transformer are less noisy

11) You can get LEED points with FR3 filled. I think its is because of innovation or possibly because it is a renewable oil

12) FR3 filled units are cheaper to decommission and dispose.

13) FR3 Filled units cost about the same as a dry type.

You can get more info about the Biodegradable oils from the Manufactures. I believe these oils have a better safety record than dry types-- check with your insurance guy. They sometimes offer better rates if you use them on outdoor subs too.

Register to Reply
Active Contributor

Join Date: Jan 2008
Posts: 16
#7
In reply to #6

Re: Dry vs Oil Transformers

01/20/2008 3:41 PM

You've made a strong case for the oil filled transformers.

But i doubt if this is enough to overcome such common trends as for the use of dry transformrs.

Thank you.

Register to Reply Off Topic (Score 5)
Participant

Join Date: Aug 2009
Posts: 1
#8
In reply to #6

Re: Dry vs Oil Transformers

08/24/2009 2:29 PM

You can get more info about the Biodegradable oils from the Manufacturers.

Can any one please guide me on how I could get to know the manufacturers? How would one go about finding the details of FR3 oil manufacturers?

Register to Reply
Register to Reply 8 comments
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.
Copy to Clipboard

Users who posted comments:

dda (1); desidude (1); Ing. Robert Forbus (1); issa David Talamas (1); ktel60 (1); nesubra (1); Ramana (1); Skipper_A (1)

Previous in Forum: Wattmetric protection in main High Voltage supply   Next in Forum: Death by van der Graff generator

Advertisement