I would like, if possible some views on new vs refurbished oil filled power transformers.

We have on our site 2 off 1500 KVA 11kv/3.3Kv oil filled transformers. Regular oil checks and more recent in depth paper analysis has identified that the transformers are reaching the end of their lifes with estimated degree of polymerisation at around 300. Due to the difficulties of removal (they are both mounted in seperate underground chambers) and the amount of civil work required to extract them, I wish to plan for end of life and try and get funding to replace them. For reference the transformers are in excess of 50 years old! I have had prices for new and refurnished transformers to replace them with and I wish to get some views on how sensible it would be to replace with refurbished units. The refurbished units come with 3 years guarantees, I dont wish to fall into the false economy trap and have to replace them again shortly after 3 years.
Would I also be right in assuming that refurbishment of 50 year old transformers is not really a viable option? I base this on the fact that the paper has degraded so much that major work to refurbish would be required, making this option financially unviable.
I have had the views of salesmen to date so a few independent views would be most welcome.

Many Thanks

Mark

Transformers are usualy long life items of plant and I have no problem using refurbished units.
The cable box flanges are important will they take a standard BS box? Get rid of any cast iron cable boxes, if they explode they are like a frag bomb. Can you change to dry cable boxes? this makes jointing and maintenence much easier. Can the transformers be resited to a better location? Is bunding required? what about fire regs? The new or refurbished units can be fitted with breathers which can extend the life of the units. You can also fit teperature sensors which can be linked into a SCADA system.

'Refurbished' is a bit of a vague term - I think I would want to clarify exactly what the starting condition of these transformers were prior to refurbishment and what work would be done to them to refurbish them.

It could mean anything - it could have been rewound, it could be a unit which has failed and been repaired, it could be a surplus transformer that has been maintained and repainted.

Also, given that you're planning to replace the existing transformers based on insulation condition (presumably based on furfural measurements?), your refurbished transformer, if not rewound, is likely to be somewhat aged already, you'd want to confirm the insulation condition/furfural levels of the refurbished unit - preferably before refurbishment and oil replacement/processing.

What sort of service life do you need from the replacements?

If the normal load on the transformers is less than 1500 kva then why do anything?? Just know where to get a replacement when you need it.
CliveS