problematic transformer oil purification
problematic transformer oil purification
(OP)
I am experiencing persistent problems with oil quality on a 5 MVA 11/6.6kV transformer. Moisture levels from samples taken twice yearly are consistently high. We do in situ oil purification annually but the problem returns after a few months.
A local company has suggested removing the transformer and shipping it off for stripping and core drying.
The task of removal of such transformer is both massive and costly and I don't want to do this unless it is really necessary.
My personal view is to re purify the oil and take 48 hours to do it instead of the usual 24 hours or repurify twice a year.
Anybody got any suggestions on a remedy?
A local company has suggested removing the transformer and shipping it off for stripping and core drying.
The task of removal of such transformer is both massive and costly and I don't want to do this unless it is really necessary.
My personal view is to re purify the oil and take 48 hours to do it instead of the usual 24 hours or repurify twice a year.
Anybody got any suggestions on a remedy?






RE: problematic transformer oil purification
In case the tank of the transformer is capable of full vaccum, you can dry out as below: Do hot oil circulation for 6 hours to heat the inside parts.Drain oil and fill with dry air or nitrogen. Keep for 6-12 hours. Take dew point at the end.Apply vaccum for 12 hours. Oil fill.Do hot oil circulation again.Repeat as above. Usually when the insulation is fully dry a dew point of -30 at 30C will be got.But old transformers need not be dried to taht extent as due to shrinkage of paper and pressboard the windings will become loose.
Before starting the dry out make sure the transformer is leak proof and pressure tight.
RE: problematic transformer oil purification
RE: problematic transformer oil purification
RE: problematic transformer oil purification
RE: problematic transformer oil purification
best wishes
Steven
RE: problematic transformer oil purification
http://sdmyers.com/EP-drymax.html
RE: problematic transformer oil purification
RE: problematic transformer oil purification
RE: problematic transformer oil purification
Really, moisture should not be a problem for years after a good drying, assuming that your transformer is NOT vented to the atmosphere or leaking badly. A competent contractor will take care of the details of performing the work, do oil samples before the work, immediately after the work, and then at periodic intervals to see where the moisture stabilizes after remediation.
Realize that the oil will likely be much lower in moisture, but the process will also move much moisture from the cellulosic insulation, too. It will take a period of time for the two systems, oil and cellulose, to reach an equilibrium at a given internal temperature. A sample a month after treatment and a couple more samples at quarterly intervals will help you understand the situation.
old field guy
RE: problematic transformer oil purification