Issues with miscibility of two transformer oils

[sohaila7]

Hello

We have two types of tranformers from China. One is 150MVA and the other one is 10MVA.

We are not sure of the type of oil used in these transformers.

Are there any miscibility tests that we can do before buying oil from local market?

What precautions need to be taken?

Which standards (IEC) deals with miscibility of oils?

Whom can I contact for furhter help?

 

[racobb]

I would contact the transformer mfg for each to start with. If it is mineral oil I would expect no problems, but I am not a chemical expert. Sounds as though you don't have any info on the type that was installed at the factory for either unit?

Alan

 

[prc]

Make sure that 10 MVA transformer is filled with mineral oil and not any fire resistant oil (eg esters etc)Mineral oils are governed by IEC60296(ed3.0)-2009. Generally mineral oils can be mixed without problem up to 5-10 %by volume without any problem.If these are new transformers problems may be less as the oils may be superrefined ,inhibited, paraffinic oils.

If you want to mix more, or to check suitability correctly , prepare oil samples as per the proportion you want to mix and conduct oxidation stability test.Compare this result with individual oil oxidation stabilty test results. It should not be far worse than individual results.

 

[sohaila7]

Thanks for all the replies. Actually we want to procure oil to be kept on site for topping up purposes.

Before placing order for any oil which tests we can run oils in our two transformers to determine which oil we should purchase that is miscible with oils in our transformers and in which proportions?

Does anyone knows about tests that can be performed on oils to determine if an oil is parafenic or napthenic, inhibited or uninhibited and to determine which IEC class it belongs?

Which oil suppliers I should contact for getting further information?

 

[ScottyUK]

Asking for service providers without giving your location is an exercise in futility, but two good companies in the UK are Electrical Oil Services Ltd (ex-Castrol) and Transoil Laboratories. EOSL provide a full service from supply, oil processing, testing, disposal. Transoil are a specialist test house.


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

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

 

[THD]

My instinct would say that the Chinese trafo is using a parafinic (single chain molecule oil). The naphthenic (branch chain) is more expensive. Its not good practice to mix oils. I made that mistake before on a 40MVA Crompton Greaves Trafo. I was thinking (its English - must be Naphthenic). They are made in India these days - and the trafo was filled with Parafinic oil!!!

Kevin Bosch
Rainbow Technologies

 

[THD]

Both from China - probably both Parafinic - but you have to do the tests. And dont forget the breakdown test, crackle test, dissolved gasses etc whilst you are about it. Dont want to do the job twice.

Kevin Bosch
Rainbow Technologies