Settings the ONAF operation of Power Transformer
Settings the ONAF operation of Power Transformer
(OP)
We have a power transformer with two stages of ONAF, it has two groups of fans.
According to the results of the CO2/CO, the values are greater than 10, and It is suspicion of cellulosic degradation due a over thermal. I want to know, how to set the start of the fans. I want to decrease the start of the fans, however I do not which will be the way the set the new values.
According to the results of the CO2/CO, the values are greater than 10, and It is suspicion of cellulosic degradation due a over thermal. I want to know, how to set the start of the fans. I want to decrease the start of the fans, however I do not which will be the way the set the new values.






RE: Settings the ONAF operation of Power Transformer
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Settings the ONAF operation of Power Transformer
RE: Settings the ONAF operation of Power Transformer
How old is the transformer? Has it been in continuous service since its manufacture? If it has been in storage, what records do you you have of [a] proper mothballing having been performed, [b] proper storage conditions having been maintained during hibernation, and [c] proper re-commissioning steps having been done?
What is the temperature rise of the transformer?
Have you confirmed an over-temperature situation actually occurred? Is/are there mechanical oil or winding temperature gauge[s] with drag hands to confirm this?
Absent such evidence, you may wish to consider whether the xfmr has manufacturing defects that may be covered under warranty...
CR
"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]
RE: Settings the ONAF operation of Power Transformer
I have found the thermostats that control the fans. But, which will be the setting values? Is there any rule/standard?
According to the IEEE C57.104-2008, greater values of CO2/CO implies cellulosic degradation due a over thermal. Our values are around 19 and 11.
The year of manufacturing is 2001, therefore 17 years old. It begun the operation in June 19,2002. I think, it has a continuously operation, however the period of maintenance is almost 20 days per year. The power transformer (generation) has all the test routines applied, and it seems that everything is good. The temperature rise (in the plate) is 65 C. The transformer has three temperature gauge: T_HV, T_LV and T_OIL. The average values of these in 2016 were: T_HV=60.6 C; T_LV=52.0 C and T_OIL=48.2 C.
The principal concern is the CO2/CO values, greater values implies over-thermal.
Thank you for your help.
Best Regards,
Marco Antonio
RE: Settings the ONAF operation of Power Transformer
IEEE C57.91 gives describes loss of life calculations and a method to calculate the approximate temperature reduction each bank of fans may provide.
Paper degradation due to temperatures is nonlinear, so an average annual temperature doesn't tell you much. Running at 110C degrades the paper approximately 8.5 times faster than running at 90 C.
RE: Settings the ONAF operation of Power Transformer
RE: Settings the ONAF operation of Power Transformer