Water inside transformer

[Jed057]

The transformer damaged and We found a lot of water in side transformer after we did detank in factory.

We tried to investigate the reason why water ingress to transformer.

Many time we found the water accomulated the bushing box as this cable box didn't follow IP54 and I suspected that water can penetrate from bushing gasket on top during heavy rain for long time in case we never filled up the oil to it.

But vendor didn't agree with our suspection as they mention about

Transformer alway has positive oil pressure ,due to it has the conservator on top sothat transformer will not allow water ingress into transformer.

So my question is above mention is correct or not ?

When is transformer negative pressure or pressure down ?

What is the possible reason water coming inside the transformer ?

Please help !!!!

 

[waross]

Water may be generated from the decomposition of the insulating materials used. Rather than leaking in, the water may be the product of the transformer failure. If water has leaked in, you may see signs under the gaskets. Water may have entered the top of the conservator.
If the transformer does not have a pressurization scheme such as a dry nitrogen supply and possibly a diaphram in the conservator, at least the top of the conservator may be subject to negative pressure during periods when droppng ambient temperatures and/or dropping loads reduce the transformer temperature.

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

 

[WindTurbinesAreFine]

GE Makes a unit called the Hydran that measures the health of the transformer:

http://www.gepower.com/prod_serv/products/substation_md/en/downloads_en/hydranm2_fact_sheet.pdf

As Waross mentioned, the water in the transformer tank could very likely be a result of a breakdown of materials on the inside of the tank.

We used the Hydran unit on a job we just finished, and it has many alarms for moisture and gas quality. It's a useful addition for such an expensive piece of equipment. (No, I don't work for GE.)

 

[jghrist]

Many time we found the water accomulated the bushing box as this cable box didn't follow IP54 and I suspected that water can penetrate from bushing gasket on top during heavy rain for long time in case we never filled up the oil to it.

How can this be if the transformer has a conservator?

 

[ausphil]

How much water are you talking about? If you are talking about free water, then I would be thinking about water ingress or it being there from a fill, but if you took an oil sample and it showed some tens to hundreds of parts per million of water in oil (and the transformer has seen significant service), then paper decomposition would certainly be a possibility, as Waross mentioned.

Water can enter a transformer through a number of routes. As mentioned, through the bushing gaskets, but also you may have put the water in during the filling process with contaminated oil, entry into the conservator if it isn't sealed and you haven't got good moisture control on the breather, etc.

A transformer manufacturer will generally say that their design isn't to blame, but did they actually offer any useful explanation as the problem?

What sort of damage was it? did the tank rupture? What size transformer was it? Could it have got water in it during travel to the factory?

Probably more questions than answers, but there probably needs to be a little more info to make an informed decision on.

Ausphil

 

[edison123]

Probably a corroded conservator tank that had developed holes at the top. Also, the conservator tank needs a dehydrant filled breather. May be the dehydrant (normally silica gel) was saturated and let the moisture in.

Muthu

http://www.edison.co.in

 

[prc]

Manufacturer has some point. BUt water might have entered through seals above the oil level.Is this a new transformer recently installed?By follies during installation/transport considerable amount of water can be collected inside the transformer.In operating transformers large quantity of water can enter through viscous flow of wet air through poor seals, oil pumps etc ( esp after a rain which create sudden pressure gradient).Water generated by oxidation is small compared to water entering from outside.You can get a good knowledge on the subject from CIGRE brochure no 349 of 2008, " Moisture equilibrium and moisture migration in transformer insulation systems."CIGRE members can down load this booklet and similar valuable technical studies free of cost from CIGRE site, e-cigre.org.

Some time back I found free water at tank bottom in a new transformer just before commissioning. IR between core and tank was showing zero. This water was from oil in the drums. When you check oil from a drum, you should use a sampler thief as water will be at bottom .If you take sample from top everything will be ok ,but free water will be remaining at bottom.

You have to investigate and findout the reason.There are many possibilities.It need not be fre water.High humid air can also create such situations.

 

[TurbineGen]

If you in fact had a leak in the unit and the conservator tank was filled, I would doubt the bushing box was the cause. Does your conservator tank use a bladder? If so, was it ruptured? This would allow significan moisture into the unit, but I doubt so much as you would find free water. How wet was the dryer on your conservator breather?

There is also one more potential area. Many transformers have a pressure relief valve on their conservators. This is usually very low pressure (maybe 2 psi to move) and often bidirectional. That may have failed and allowed water ingression.

------------------------------------------------------------------------
If it is broken, fix it. If it isn't broken, I'll soon fix that.

 

[Millbo]

I would take a look at the oil processing log made during the oil filling. Post-fill oil sample results. The CMA of the oil delivery.

Other than that... With the unit having a COPS tank. The only way to get a negitive pressure inside the main tank is to have the breather pipe blocked off by either isolation valves being closed or shipping plugs in the Deisicant breather were left in after hot oil fill... or the valve or valves to the Conservator were closed while the unit was still warm.

As was mentioned earlier. There's a low negitive pressure, approx -1.5 to -2.5 psi, depending on the volume, in the upper section of the conservator if there is a bladder installed.