We have a 160Kva transformer in our power mains. Is there a specified or recommended frequency that the oil should be changed?

 

 

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The oil should be tested every 1-2 years, so if the beast is older than that you need to get a specialist company in, it's not DIY.

 

BUT Doesn't the transformer belong to MEA/PEA (who should be doing the maintenance) even if you paid for it?

 

In reality, transformers go on forever even if horribly neglected.

 

Where can the oil be tested?

The transformer does not belong to MEA/PEA. It was an option during construction to purchase the transformer and place it within our property boundary. We purchased the transformer. This negates the possibility of future development in the proximity to tie in to our power supply, thus lowering the possibility of power fluctuations. So far, we have had a very stable power supply to the property.

The installation is 22 years old now. We have done one oil replacement in the past. The transformer never operates near the rated capacity, so overheating should not be an issue. I do have some concerns (possibly unfounded) of moisture ingress due to rain or condensation.


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Actually PEA should be able to sample and test your oil (ask at the local office), I certainly wouldn't be doing it myself.

 

If the oil looks clear and not yukky through the inspection / level window I wouldn't be overly concerned. 

 

When you last changed the oil was it on a recommendation or simply that it seemed about time?

Actually PEA should be able to sample and test your oil (ask at the local office), I certainly wouldn't be doing it myself.
 
If the oil looks clear and not yukky through the inspection / level window I wouldn't be overly concerned. 
 
When you last changed the oil was it on a recommendation or simply that it seemed about time?

Last oil change was done on a whim. No specific reason. Turned out to be quite costly. Is transformer oil typically expensive?

Yes, major maintenance on our power supply ( high voltage an main distribution panel) is always done by qualified 3rd party.


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Transformer oil is not cheap, the last time I acutally priced any was xx years ago for a Heathkit Cantenna (https://www.radioworld.co.uk/second-hand-heathkit-hn31-cantenna-dummy-load) and it gave me a heart attack then, the Cantenna ended up filled with Castrol GTX which seemed to work just fine (no, that is not a recommendation for your transformer).

 

Luckily the oil doesn't really wear out and only needs actually replacing if it becomes contaminated, hence the "annual" testing. I would contact PEA or your trusted maintenance chaps to get the oil tested if it's more than a couple of years since it was replaced.

 

Thanks for the information


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Most interesting topic, I have my own 50Kva transformer and no way does it get used to anything near capacity but wife is always on at me to get the oil changed. 

 

I checked with a European friend who is an HT engineer working on power distribution projects and power stations worldwide,  he said much as Crossy has said above. 

Two words - condition monitoring

 

Three other words - maintenance induced failure

 

Read up on these is my suggestion and make an educated decision. In the industrial world we use many inputs to decide on a particular maintenance strategy. In the case of transformers it is based on condition monitoring I.e as has already been suggested - oil testing. Many years ago it was time based but this is too expensive and can lead to maintenance induced faikure.