running wet tranformer dry

[judylev]

I have a 30kw 3ph 440volt compressor and a 10,000 volt line. I want to install a 100 KVA transformer that I own but I can't get the 50 gallons of oil up to the remote site in the same truckload so we will have to wait a month for another delivery.

Can I run this transformer dry with intermittent 30% loads without oil?

 

[alehman]

NO! The oil provides electrical insulation. It will probably fail instantly if you energize it without oil.

 

[waross]

KABOOM !!!

Bill
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"Why not the best?"
Jimmy Carter

 

[rbulsara]

Do you think the manufacturers add oil in transformer just to make up weight or lubrication?

 

[judylev]

That is some good advice! thanks.

Can I use old oil then?

I assume that blackened mineral oil contains insulation debris and molecular fragments and oxide products none that would degrade the heat transfer ability but I suppose could come with a corrosion risk. Filtration would improve color for what that is worth but would common chemical contaminations affect the electrical properties?

 

[Zogzog]

Dont use old oil, there can be all sorts of bad stuff in there. There is no decesion to be made here, have it filled by pros, have the oil and the transformer tested before you energize it. Find a company near you at

http://www.netaworld.org

Most failures occur after moving transformers, this is a vital time to have it tested and you oil tested including DGA analysis. All of your test data (TTR, IR, PI, Pf/Df, winding resistance, etc...) will be your baseline data for future testing and vital for condition assesment.

 

[ScottyUK]

Like what, old engine oil? Are you crazy? Transformers use electrical oil to IEC296 or whtever your local equivalent standard is. They use this for a reason, which is that the oil is designed for the purpose and the transformer is designed to use this oil. You can't just substitute other oils at will.

If you want to kill yourself by taking shortcuts with HV electrical work which you don't really seem to understand to any great level then frankly that's up to you, but if you take shortcuts and manage to kill your workmates, or employees, or bystanders then that is altogether more concerning. Please do the job properly or don't do it. Get help from someone who has experience.


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

 

[validtech]

All above reactions are perfectly correct.
However, I know how it feels having big pressure for electrical power availability, and been lost in the sand somewhere...

Assuming your 'old oil' was the one filled in the transformer before moving it, you could at least performs as follows:
1) take some oil samples and ship it to a specialised laboratory for basic tests: dielectric, PCBs...
2) check with your supplier (have it confirmed in written) that old and foreseen new oil can be mixed / at least they are equivalent (by the way, what oil type is it?)
3) check arround for a filtering unit, PCB free (!), fitted with vacuum pump and heaters.

At my opinion however, it will not be much faster filling and treating the 'old' oil, taking the capacity into account, than waiting for the second truck... Check-out!

Phil

 

[rbulsara]

judylev:

You received the correct answer in the very fist response from alehman. What more do you want?

If you understood the function of the transformer oil, you would not have asked the question.

 

[edison123]

A 100 KVA trafo would weigh 3 tons tops, with oil. So, why was the transformer trucked without oil ?

50 gallons of oil would weigh about 250 kgs, which you could transport in a pick-up.

 

[alehman]

Please do not put old oil in the transformer unless it has been tested by a qualified testing agency and certified as usable for that purpose. Transformers require a special grade of highly purified mineral oil. If the oil is contaminated it could destroy the transformer.

 

[waross]

I once observed a small drop of dirty grease in the adjusting screw thread of a workers adjustable wrench loosen and mix with the transformer oil when connections were being changed below the level of the hot oil. The transformer failed about two hours later.
Your best bet is to have the transformer filled at a qualified shop and transported to the site with the oil in it.
Not as spectacular but a lot cheaper over the course of a few hours or days.
Really, from the questions you are asking, there is a high probability of early transformer failure if you attempt to fill the transformer without experienced help. It is a little more demanding than pouring a quart of oil into the engine of the truck.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[prc]

Very interesting discussion!
In 1920's GE supplied a medium sized trf to a US utility.Oil was supplied separately.User forgot to fill oil and energised transformer.It worked for some years( demand for electricity must had been quite low) untill the load increased.Fumes came out with fire.When opened out they found the instruction manual also tied to the active part of trf!

On another occasion, a chief engineer as pressed as judylev, faced with a shortage of oil.He put tap water in to transformer through bottom valve till the level of bottom windings. Oil remained at top of water to cover the windings and transformer was put in to srvice.

Sorry, todays transformers will not stand any of these innovations.It will give you really bad surprises !

 

[jasonf987]

Mineral oil is the most common insulating medium and provides four functions that contribute to the operation of a transformer:
•Dielectric strength – acts as a dielectric and insulating material.
•Heat Transfer – acts as a cooling medium.
•Protection – acts as a barrier between the paper and the damaging effects of oxygen and moisture.
•Testing tool – acts as a diagnostic tool for evaluating the solid insulation.

Solid material is used as insulation due to two distinct properties, it has the ability to withstand both electrical and mechanical stresses at voltages used. Thus any insulation system needs to meet at least four requirements to ensure effective insulation:
•Be able to withstand high voltages in normal service together with impulse and transient surges.
•Withstand mechanical and thermal stresses under short circuit conditions.
•Prevent excessive heat build up.
•Retain desired characteristics for a satisfactory service life period.

There are certain other aspects which affect the insulation aging process, an example is hottest spot temperature above 90-105 ºC which will cause irreversible damage to the cellulose insulation of a transformer. This deterioration occurs over time until the insulation fails. Moisture content in the insulation also has a significant impact on the insulation aging, if the moisture content increases from 0.5% - 1% the rate of aging of the cellulose insulation at least doubles for a given temperature.

Any weakness of insulation can result in the failure of a transformer, which is criminal as these conditions can be monitored and prevented.

Best advice, use the correct equipment for the application and don't try take a shortcut, especially when it comes to transformers.

 

[controlsdude]

Old oil?

If you get some old transformer oil it might be contaminated with PCBs. I would even test the oil that you are putting in to make sure that it is good transformer oil.

Used to work in a transformer repair shop and one the the lead guys was adament on testing any oil brought in to make sure it was not contaminated with PCBs. It caused the trucker some headaches but it saved the company later grief if you got PCB contamination or just bad oil.

 

[waross]

If the transformer has been sitting for any length of time without oil it may fail soon in any event. Many transformer people are wary of energizing a transformer that has sat for several years even with oil in it due to the possibility of moisture contamination. The transformer probably should be vacuum dried before being filled with good dry oil. If this is a critical application, forget the old transformer and buy a new one.


Bill
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"Why not the best?"
Jimmy Carter

 

[ScottyUK]

Does no one else see a problem with the word 'blackened' in relation to transformer oil? (post of 11 Jan 09, 11:50)

Black transformer oil?? FFS.


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

 

[edison123]

Is it like tar/bitumen ? After all, they were once used as insulation for motors & generators

 

[alehman]

Yeah, I missed that. I think it's a safe bet to say don't waste any money testing that.

 

[waross]

I'm with you on that Scotty;
I can't help thinking,
"Photo Opportunity!"

Bill
--------------------
"Why not the best?"
Jimmy Carter