Maintenance for Transformer

Just from the top of my head.

You can also check if Bucholtz relay (if present) is connected properly. OLTC and RTCC are properly configured. All terminating cables are in proper condition.

Regards.

you can also check the power factor. and if necessery can add a capacitor bank to improve the pf.

From your list I would put #3 at the top. I think 5 years if too long in between checks. Maybe someone can provide a suggestion as to how long in between checks.

Oil tests should be done annually. Other testing typically on a 2-3 year basis, depending on how critical the transformer is, how heavily it is loaded, and what the results of the oil tests show. See the NETA (International Electrical Testing Association - www.netaworld.org) Maintenance Test Spec for information on tests and their Frequency of Maintenance Tests guide (free download) for intervals.

https://netforum.avectra.com/eweb/shopping/shopping.aspx?site=neta&prd_key=af5326f4-de81-488f-96d9-8707d514e687

https://netforum.avectra.com/eweb/shopping/shopping.aspx?site=neta&prd_key=af5326f4-de81-488f-96d9-8707d514e687

GA, We test the oil on all our transformers annually. We also conduct visual only inspections on the low voltage side, looking for obvious signs of heating or damage on a monthly basis.

Dear Sir,

Add Transformer Oil Filtration & Testing for BDV.

Manroop.Chennai.

Do you have a glass container on the side of the transformer with silicon crystals in it?

If not then no worries, if you do... check the colour, and change out if more than 50% of the colour has changed and as other posts have told you test the oil.

If you change all the oil and a Bucholtz is fitted, then refill SLOWLY over a few days to allow the air trapped in the windings to escape, otherwise your TransX will trip due to air tripping the Bucholtz as the windings get warm and the air finds its way out and up.

Hi!

Since you are carrying out maintenance after 5 long years you may go for the following also:

1. DGA of oil (Dissolved Gas Analysis)

2. Carry out oil filteration

3. Replace silica jel in the Si jel breather, if not done recently.

4. BDV of oil before and after oil filteration.

BB Raina

Hi all:

Thank you for your input, I remember that the oil of this transformer is checked annually. As I saw that the transformer itself is very dusty, so as a matter of fact, we need to clean its bushings. The other tricky question, how we will do this? By clean cloth or by water?

Yes, we can disconnect the cable. But it is known that we can check the insulation only. We should not do any test on this cable. Why? Because it is old and the test voltage is much higher than operating voltage. This would damage the cable, wouldn't it?

After all the work is done and the data is nice. Is that safe enough to switch power back on? Another question comes, if you were me, do you ensure that there is not any problem with energizing power to transformer? I was threaten by one colleague that he used to damage his transformer after doing maintenance. The transformer bushing is on fire after energizing. The root cause remains unknown... Yes, we don't know if it is true or not, as an experienced, what you will say to him?

Regards,

read the instructions on a firework and apply when energizing your transformer, if you are that worried about it!

As for cleaning..... use a clean cloth, NEVER water or any type of chemical cleaner

One reason I liked old GEC OCB's you could charge the closing springs then tie a lanyard to the closing lever and then clear off to safe distance. Much better than light blue touch paper and retire immediately.

Hang on I'm retired, it's coming up to November the 5^th, I can't light my fireworks!

Maintenance of Transformer is very much linked with the followings:

Type of Transformer - Indoor or outdoor.

Age of the Transformer.

Environment at which the transformer is operating including the load cycles.

The testing equipments/ instruments available in plant including hiring facilities.

Cmpetent Engineers/ Technicians availability.

Considering the above the following basic tests can be carried out:

IR value

PI and AI value

BDV test of insulating oil

Moisture content test of oil( Frequency Domain Spectroscopy/ DGA/ Karl Fischer Titration test)

Checking of OTI and WTI

Checking of radiator banks,diffirent valves,oil pielines.

Checking of connection in marshalling box.

Checking of Buchholz relay and OSR.

Checking of breather including silicagel.

Cable terminatins and if there are outdoor bushings the same should be checked.

Filteration of insulating oil with vacuum oil filteration plant( with 760mm of Hg.column)

Checking of winding resistances, turns ratio/ voltage ratio.

Checking of operation of OLTC/ Tap changer

Magnetic balance test,Checking of neutral grounding( if neutral is available)

Checking of functioning of M.O.G ( if fitted)

Checking of conditon transformer base wheel locking.

Checking of functioning of protective relays.

MONITORING OF SOUND DUE TO VIBRATION OF CORE IS VERY MUCH ESSENTIAL WIHCH CAN INDICATE IF THERE IS ANY LOOSENESS IN CORE STUDS AND BOLTS.

Concerning Silica Gel breathers this previous post might be of interest

http://cr4.globalspec.com/comment/312638