Oil leak from transformer secondary bushing
Oil leak from transformer secondary bushing
(OP)
On site we have a 2 MVA oil filled transformer 6.3kV/0.42kV. There is a small leak form the bushing base connection to the transformer tank. We want to replace the gasket of the bushing. Is there any procedure for this kind of activity? I guess that the bushing needs to be lifted somehow, take out the old gasket and replace it with the new one. But also the tank oil will be exposed to atmosphere also we might need oil recirculation and o2 measurement and of course during the work execution to make a small kiosk around the area with the use of dehumidifier. Any proposal will be appreciated.






RE: Oil leak from transformer secondary bushing
I don't think bushing diassebmly/maintenance is a typical field job. If you're doing it, you certainly should have on hand someone that has already done it. One paramount concern is that when you're done there is no moisture remaining in the bushing paper, oil or gas space.
There are other standard procedures for opening transformers, considering moisture exclusion, personnel safety etc. This also is something not to be done without someone onhand that knows how to do it.
Sorry if my response wasn't productive. In general I'm not a fan of motherhood responses and maybe I'm not quite understanding your question/situation. Also maybe I am erring on the conservative side as far as bushing maintenance, I know we considered it once and elected to swap it and have maintenance done by OEM instead. I have worked with big oil-filled transformers, not small ones.
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(2B)+(2B)' ?
RE: Oil leak from transformer secondary bushing
RE: Oil leak from transformer secondary bushing
RE: Oil leak from transformer secondary bushing
There are many good quality epoxy sealing compounds available in market.You can apply and seal the leakage.Drain oil from tank till just below the bushing to stop the oil leak before applying sealing glue.
Most probably the type of bushing will be such a type that you can change the gasket from outside.Please see the instruction book for bushing details. or post a photo of the leaking bushing so that I can suggest.
After changing gasket or after curing of seal, top up the drained oil back in to transformer. Leave it for atleast two days before energising.
RE: Oil leak from transformer secondary bushing
Now I see it can also more logically be interpretted as (B) a leak from between bushing and tank. No need to tamper with a gasket integral to the bushing. May also be a draw-lead bushing.
If it is in fact B, I withdraw my comments.
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(2B)+(2B)' ?
RE: Oil leak from transformer secondary bushing
RE: Oil leak from transformer secondary bushing
you can't fix stupid
RE: Oil leak from transformer secondary bushing
RE: Oil leak from transformer secondary bushing
Typically once the transformer is proven de-energised, the biggest risk we need to manage is of oil spills and subsequent environmental cleanup issues.
The point I wanted to raise was with Smallgreek's suggestion of using dry nitrogen during the repair - be very, very careful of using nitrogen in this manner (ie with work crew in vicinity of open transformer flange) as the nitrogen will alter the breathable atmosphere surrounding the bushing flange and can lead to nitrogen asphyxiation. There are numerous documented cases of fatalities when using Nitrogen as a purge gas:
http://www.csb.gov/newsroom/detail.aspx?nid=261
http://w
If our risk assessment identifies the need for controlling the ingress of moisture to the transformer, we would use dehumidified air.
RE: Oil leak from transformer secondary bushing
Drop oil level to below bushing level (have spill kits ready, just in case).
Make sure it's a "dry day" (I would not be doing it in 60% humidity).
Account for the loss of a bushing (break during handling).
Undo lid, replace gasket, making sure you use you use rubberised cork gasket (TG70 / 70% rubber)...
Clean your surfaces with a solvent like ISOWash or something similar...
Put everything back together... Maybe take the change to get an oil sample for DGA and DAM analysis before and after, if you can...
I hope that helps...
Dan de Freitas