Storage of NEW power transformer

[jmomic]

We have to store new transformers for at least 2 to 3 years.
I understand that filling with oil is the best option. Do we need to mount all radiators and conservatory tank if we want to fill the oil in (this would be preferable as per manufacturer)?

What do you think about keeping it filled with nitrogen?
How to keep radiators, piping and conservatory tank dry if not assembled on the casing?

Would the dry transformer core damage the impregnation of the paper and cause possible cracks?

Thanks in advance for help

thread238-262209

 

[Marmite]

Personally I would follow the manufacturers guidance otherwise you will have warranty issues if anything goes wrong when you eventually energise them.
Regards
Marmite

 

[prc]

You need not mount radiators,but conservator plus breather is a must.Definitely you should keep under oil if storage is for more than 6-12 months.Problem with keeping with gas only is the chance of moisture ingress through seals and oil draining out of paper.There were cases of EHV tarnsformer failure where long storage was under nitrogen.

 

[DTR2011]

Connecting control power for cabinet heaters is also a good idea.

 

[jmomic]

I know that the following of the manufacturer guidance would be sure bet. The cost is factor as well. It would be impossible to move transformer with rads on and cost for dissasembly and reassebly is high too. There is no way to have it energized as well.
I am planning to get the power for control cabinet. This is workable.

I do not want to risk the health of the transformers (2 are in question) but also would like to save on unnecessary cost.

All your comments are helping my case.

Did you have any experience moving large transformers 250MVA 242/18kV with radiators on if storage is on the same property as the final location (no road restrictions)?

 

[DTR2011]

"Did you have any experience moving large transformers 250MVA 242/18kV with radiators on if storage is on the same property as the final location (no road restrictions)? "

There are some situations where this is done (large generating stations), however from what I've seen, there is also built in rails for moving units around. I've seen this in some German influenced areas and also the US. I believe this is a long ago design (1970's?)

I have seen several large GSU units in the US stored long term without radiators or bushings installed. That seems to be what is done now.

Installing the radiators and adding oil is a fairly simple task in transformer assembly. I would not feel good about trying to move a unit with the radiators & bushings installed, considering the risks involved with an accident and environmental cleanup involved. You may want to check with rigging / heavy hauling companies that specialize in this work and find their comfort level. I'm not an expert in this area, but simple things like how the unit is balanced (equal radiators, etc), do lifting provisions exist without interfering with radiators...

Additionally, you have not mentioned the conditions for travel and the distance you have to move the units. If it were paved concrete roads that is one thing. If it is a wet, muddy switchyard in the springtime, that is another.

 

[jmomic]

The condition for movement would be something between. Hard packed construction fill. Depending of the final space allocation we may need to move it just the distance to allow to make the concreete pad. It may be moved with the crane if possible to get the crane for this load to the site.

The issue is that we need to decide about temporary storage, moving to final storage and then moving to the final position.

At this moment everything is unknown.

 

[waross]

You may consider, and it may be feasible, to energize the transformer with a low voltage and possibly a short on the other side windings to generate heat internally.

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

 

[prc]

Waross, small voltage will not help. To get full load current, 25 MVA at 1.8 kV or 24.2 Kv will be required( assuming 10 % impedance).Even assuming 20 % current is sent ( with coolers blocked) a small distribution transformer will be required. Of course some utilities have tried it, but frankly these are not required. Today's transformers have an air cell inside conservator which will prevent contact with outside air. A good, well maintained breather over the air cell will prevent any moisture ingress. To day spare single phase transformers in HV DC converter stations and EHV single phase Auto transformers are maintained such that in the event of failure of a single phase transformer, immediately the standby will be switched in with minimum delay. These transformers are not heated up -, but oil is circulated by their own pumps once a week or so.

In this case only temporary storage is involved. Oil filling with conservator and breather will be more than enough.Another way is tank alone is filled with oil leaving approximately 10% of tank height with dry air and monitor the air for positive pressure.This is the normal storage practice followed at site.

 

[bacon4life]

The attached file shows moving a 242/115 kV 400 MVA transformer fully assembled and oil filled. It was basically the same gear they used to offload from the truck when it was first delivered.

There does happen to be concrete rails in this picture, however they were part of the original 1950's design and not large enough to accommodate this transformer. The rest of the move was across the gravel yard, then up over the oil containment berm. The cribbing system can be set up on most types of surface. When a similar transformer was scheduled for delivery during the wet season, the mover indicated it could still be done by first laying down large steel plates over the mud.

On 115/12.5 kv distribution transformers we have done temporary storage without radiators.

 

[prc]

I was witness to moving a fully assembled 31.5 MVA 220 kv Station start up transformer in a Nuclear Power Station.Running transformer failed due to a dead short circuit on secondary. Using a huge mobile crane available with the utility, the failed transformer was lifted and moved to a near by store yard. An identical transformer was taken out from a nearby plinth and put on the plinth where the faied transformer was in service.

 

[bdn2004]

We just recently moved some large transformers which included a new GSU at a power plant. A company named Barnhart did the work. These people know what they are doing.

 

[jkristinn]

As far as I understand, the reason why manufacturers guidelines say that coolers should be mounted for storage, is just to keep the coolers dry as well. As long as the coolers are stored at dry location with stable temperature there is no need to mount them during storage.I wonder if the manufacturer would confirm this at a request, so there won't be consequences.