UK 11KV/415 lack of transformer breather and effect on life

[UKMeterman]

Hi all,
I am aware of a 1.25MVA 11KV/415 transformer that is plated as oil cooled that was put into service in 2008 without a silica gell breather, the breather pipe has just been left open. Two smaller 500KVA units in the same compound one has an expired (wet) breather. What would be the affect on the life of the transformer and also what would be typical / worst case when the transformer faults.

What is the replacement cost of such a unit / cost of repair and how much are the breathers?

Thanks

 

[alehman]

affect: likely significantly reduced transformer life due to atmospheric moisture in the oil

typical fault scenario: protection relay trips or fuse blows and transformer is de-energized

worst case scenario: transformer explodes when it faults showering the surrounding area with flaming oil. Buildings catch fire and the entire neighborhood burns to the ground. People are injured. Lawyers get involved and there is major environmental cleanup required because it turns out the oil contained PCB's. People die because the emergency generator in the hospital it was supplying didn't work.

replacement cost: I don't know. Call a transformer mfg.


Alan
“The engineer's first problem in any design situation is to discover what the problem really is.” Unk.

 

[ScottyUK]

Meterman,

Depending on who you buy it from figure on about £20k - £25k for a one-off. The utilities may get discounts on that from the big OEMs, and there is always cheap crap for fools to buy.

Agree with alehman on possible problems.

You can probably prevent further degradation if you get someone like EOS to process the transformer and oil using vacuum and heat, although the rental costs of an Ilovac and crew will soon exceed the value of the transformer, plus not all distribution transformers are capabale of withstanding vacuum on the tank. Wyko, Winder Electrical and Dowding & Mills should be able to quote for remedials on this transformer, although a plain baking process won't be as effective at removing water from the core as vacuum. Send the oil for reprocessing.


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

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

 

[UKMeterman]

Thanks for the replies. The genral view is that the lack of the correct breathers is a bad thing. I am just a interested visitor to the site.

I am not sure if the transfomers are owned by the site or the DNO as the site has it's own 33KV substation and is listed by the DNO as metered at HV. I do know the local DNO has been performing some mantaince on the HV switchgear.

The transformers in question are directly under a 1000 person capacity nightclub. I take it that if the transformer does belong to the DNO, then they should be replacing the breathers and would not have let it get into this state. If the transformer does belong to the site then there are issues with the maintaince procedures.

 

[Marmite]

The local DNO's policy may be to not routinely fit breathers to this type of transformer. The three that I've worked for don't. The transformer is delivered with a plastic cap over the breather pipe which is taken off after delivery and then the pipe is left open. When you have tens of thousands of transformers on the system changing the breathers becomes a large maintenance responsibility. The frequency of maintaining the oil filled switchgear has increased to circa 12 years in some Companies and you wouldn't want to make a specific visit just to change a breather.
Regards
Marmite

 

[davidbeach]

In the states, transformers of that size will typically be sealed to avoid the need for maintenance mentioned by Marmite.

 

[Brownell]

Transformer Breathers are readily available to solve this problem.Typical cost is £25 to £250 pounds.