Transformer Oil Leak

If I have understood properly you mean 3.3 KV bushing

If so, Isolate Transformer, lower oil level below bushing level.

reach inspection window above bushing, open it, open back connection to stud . Remove bushing, replace gasket (O rings).

Repeat same procedure in reverse order and assemble transformer

Sorry I should have said it's leaking from around the seal between the cable box and the tank. The box is compound filled.

dear Guest,

before you do exercise as advised by Mr. Singh, please ensure that 3.3kV bushing was tightened enough (you can check with manufacturer what is the torque level for this bushing). Do not apply torque level without manufacturer's advice as it will break your bushing porcelain.

Note:

1. If transformer is still under warranty, i recommend you to contact manufacturer to fix the leakage. Otherwise contact local contractor who understand how to treat transformer there to fix the leakage on behalf of you.

2. If warranty already expired, then you can carry out exercise as advised by Mr. Singh under your own risk. But i would recommend you to:

- provide tarpaulin during bushing un-installation and re-installation to prevent dust to enter transformer.

- provide clean temporary oil storage (i would say for 1800 kVA Tx, assuming 3.3kV bushing installed on the tank cover and transformer type is hermetically sealed totally oil filled, you only need to drain approx. 40-70 ltrs of oil).

- provide a new and good gasket (preferable neophrene material).

- do oil treatment process after gasket replacement and bushing re-installation.

- check oil BDV after treatment. Should reach 60kV/2.5mm level.

I work in Transformer repair for a Government owned electrical transmission and distribution company in Queensland.

Before you do anything, are you trained in this type of repair? There are many things to consider, and if you are not familiar with this type of work I would recommend engaging those who are.

While tolerances at 3.3kV are not as significant as at 132 or 275kV, if you get it wrong you could have quite a mess to deal with. Not only will you need to consider the disposal of the old oil and supply of new, but if you are replacing gaskets around cable boxes you should also consider how you will deal with the cable and the insulating compund - if you need to remove the bushings then the cable box will need to be opened. Also, you will need to perform an Insulation Resistance test after the repair - this will require the disconnection of all cables/lines including any surge diverters from the transformer.

By the way, before doing any work on the transformer consider local HV access proceedures, earthing requirements and protection isolation as required.

Regards

Justin

I had the same problem several years back, almost the same rating transformer. the transformer was about 40 years old.

We decided that instead of partially draining the tank we would go for a total oil change, easier as the oil company came in with all the gear to drain the tank, flush it and then refill. Braking down the cable box meant heating the box until the filler at the top could be removed. More heat was then applied towards the bottom and the box cover bolts removed. By gently prying the joint at the bottom of the box there was a gap for the compound to run out in to an old oil drum with its top cut off. This took quite some time. The conservator pipes were removed and the top removed while the box was draining. Eventually the box lid was free to enable the inside to be cleared properly. The cable was disconnected and the box to tank joint undone. The box and cable then leant way clear of the tank and propped up. The bushing were then cleaned and disconnected from the leads in the tank. (It was while doing this we found the off load tap changer was over heating, so repaired that just to add a bit more time to the job). The stuffing glands were removed and new cork seals made. New seals had to be made for the tank top, box to tank and the box lid. Then JUST put it all back together again.

It's a time consuming, dirty, horrible job. But if you put it off, oil leaking in to the compound softens it, which could turn out to be an even nastier job when it goes bang!

Gaffer tape.

We're going for the time consuming, dirty, horrible job method. Yuk! Thanks to all!