Power Transformer Replacement Program & Criteria

[Beengineer]

Do you have the substation power transformer replacement program? Criteria?

Is there any publication of literature about this subject?

Thanks

 

[dpc]

Substation power transformer are seldom replaced based solely on age. Many 50 year old transformers (and older) are still in service.

Results of oil tests and other maintenance testing are more important than the age of the transformers.

And the number of through-faults, I suppose.

 

[Beengineer]

We don't officially have the power transformer replacement program. Mainly it's "time based", say 50 yrs.

As the part of the Asset Management, we are now trying to develop a replacement program that is "Condition Based".

Thanks

 

[17011980]

dpc is right! Main criteria for replacement of power transformer is the results of oil tests and measurements results like insulation level and others! Why do you ask Beengineer? what sort of problem have you?

 

[oldfieldguy]

I've worked in several petrochemical facilities and none that I am aware of have a time-based criteria.

Because of the nature of my business, all of them had specific requirements for periodic on-line and off-line testing. the data gathered were trended to note deteriorating conditions and remedial efforts were taken if one of the little things started to head towards self-destruction.

I can think of several units that went into service in 1940-1945 and they're still chugging along. Some have been rebuilt, some not, and some are and a more stringent testing regimen due to age and indications, but they're still out there. I know of one 45 kV station service transformer that was dated 1902, still in service in 1993. With the cost of replacement transformers, I'd certainly be reluctant to apply a hard age-based criteria to replacement.

I would, however, look at my more critical transformers a bit harder and take an active stance towards remediation on my schedule rather than waiting for failure.

old field guy

 

[HVDragon]

There isn't general criteria for replacement of transformers.We have 45 years 180 MVA trafo, with average load of 10 MVA and it's in perfect condition / after replacement of oil 10 years ago/, but we have 25 years 210 MVA trafo with average load of 80%, several very heavy short circuits nearby and it is in very bad condition: low isolation, high tandelta, dirty windings, etc.
There is only one reason to replace a power transformer: exhausting of isolation. Direct method for assessment is measurement of furfural, indirect method - polimerization steppe /PS/. The first trafo has PS=580, the second one - 280.
As You know when PS<250 begins process of degradation of cellulose isolation and that will be the end of the transformer.

Something terrible is stalking between the high voltage potentials