Oxygen in Transformer oil
Oxygen in Transformer oil
(OP)
Dear Folks,
Pl. explain me the significance of oxygen in transformer oil for both Bagged type conservator/ open type of conservator.
Advanced Thanks...
Pl. explain me the significance of oxygen in transformer oil for both Bagged type conservator/ open type of conservator.
Advanced Thanks...






RE: Oxygen in Transformer oil
RE: Oxygen in Transformer oil
regards
Marmite
RE: Oxygen in Transformer oil
If yours is the second case, you're also adding moisture to your transformer as the moisture in the outside air gets into the transformer.
old field guy
RE: Oxygen in Transformer oil
Additionally, O2 occurs as a result of the aging and degradation of paper insulation.
If the transformer is of relatively recent manufacture (6-10 yrs.) your oil may contain an O2 inhibitor which in effect "absorbs" oxygen and keeps the numbers relatively low. As the inhibitor saturates the O2 numbers will elevate. It is wise to have the inhibitor level checked.
I'm not sure of the exact numbers, but it seems that a level of .08% is considered to be the level at which the inhibitor is completely ineffective. (A reputable lab can verify that). If the inhibitor is forgotten, the added O2 in the oil will help the paper insulation degrade even faster.
RE: Oxygen in Transformer oil
It is well known that three factors contribute to lots of oxidation reactions such as insulation aging: temperature, water and oxygen.
An interesting illustration:
We had generator stepup transformers that were very regularly disassembled and reassembled almost every 18 months for a variety of reasons (low voltage bushing leaks for example). Don't ask me why. At our nuke plant that's the way we did things being very conservative to address even small problems. The frequent disassembly seemed to lead to more leaks and things and was self-perpetuating since we had a low toelrance for leaks.
After several drains and refills, the CO and CO2 usually grew high (in the range 1000ppm CO and 10,000ppm CO2) and came back quickly after oil drain and vacuum processing (indicates insulation aging). We chalked it up to the sustained high temperatures. Also we had quite high oxygen routinely 10,000 ppm - 20,000 ppm. Moisture not so bad 15 - 30 ppm at typical transformer oil temperatures around 70C-90C.
We had a strange event where the transformer started burping oil out of a relief. Investigation revealed the dresser couplings at the suction of the oil pumps were sucking air in like a seive and this condition existed on all those transformers. We implemented a change to a different accordion style flange that was bolted at each end and a much better seal.
The unexpected benefit: O2 went down towards much lower levels perhaps 500ppm - 2000ppm. Moisture may have went down a little. The CO and CO2 pattern went down dramatically CO2 now doesn't get much above 1,000 (even though temperatures are the same). Seems like pretty clear proof that the moisture and the oxygen contribute to that oxidation
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: Oxygen in Transformer oil
The expected benefit: O2 went down towards much lower levels perhaps 500ppm - 2000ppm. Moisture may have went down a little.
The unexpected benefit:The CO and CO2 pattern went down dramatically CO2 now doesn't get much above 1,000 (even though temperatures are the same). Seems like pretty clear proof that the moisture and the oxygen contribute to that oxidation
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: Oxygen in Transformer oil
Mr.Subtech :
Additionally, O2 occurs as a result of the aging and degradation of paper insulation: In this condition, if active oxidisation inhibitor is available, O2 will be absorbed. Then how can aging and degradation of paper insulation be noticed?
RE: Oxygen in Transformer oil
Once it was thought that O2 is the major factor in ageing of oil and transformer insulation.Today it is understood that its effect is much less than that of water and temperature in paper ageing.
It should me remembered that bag or bladder will not prevent 100 % sealing as it is permeable to some extent.Definetely it will reduce O2 and water ingress.But it will also prevent breathing out of water from paper oxidation.
Peter's experience is interesting. I believe the excess ageing would be due to the high level of moisture sucked in rather than the high level of O2 entered in to system.Is this transformer N2 sealed type or free breathing type? O2 level may have come down as no more air is dissolving in to oil.Water level in oil may not have gone up.But definetely water level in paper must have goneup.Remember, in transformers 99 % of total water is in paper and only 1 % by weight is remaining in oil.
One disturbing phenomenon noticed during last five years is the transformer failures due to corrosive sulphur from oil.This is noticed more where o2 level (ie bagged type consrvator)is low.Reason for this is not yet known.
RE: Oxygen in Transformer oil
How to find moisture in Insulation paper? Is there any co-relation with the moisture quantity in oil?
RE: Oxygen in Transformer oil
IEEE Std C57.104 guide for interpretation of gases generated in oil-inmersed transformers.
RE: Oxygen in Transformer oil
That is a tricky one. The bulk of the moisture is stored in the paper. After a period of time the oil comes into equilibrium with the moisture content of paper surface. Higher oil temperature causes higher equilibrium moisture in oil for same moisture in paper. There are charts you can use to estimate water in paper from water in oil but assumes equilibrium.
For off-line tests, as a rough rule the % power factor during insulation test is equal to percent moisture of the paper. Also dew point test with transformer drained can be used to estimate surface moisture of the paper.
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: Oxygen in Transformer oil
"dew point test with transformer drained can be used to estimate surface moisture of the paper" - Shall we need to carry dew point test of residue oil from the tank after draining? Pl. eloborate it.
Thanks...
RE: Oxygen in Transformer oil
In the meantime take a look at figure 22 on page 65/87 and figure 23 on page 66/87 - one means for estimating paper moisture from oil moisture (again dependent on equilibrium)
http://
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: Oxygen in Transformer oil
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: Oxygen in Transformer oil
Figure 8-1 provides a linear graph:
Insulation temp 10C => max dewpoint is -40C
Insulation temp 50C => max dewpoint is -15C
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: Oxygen in Transformer oil
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: Oxygen in Transformer oil
Hi.
Please see attached links, maybe it will be intresting for you
http
http://www
RE: Oxygen in Transformer oil
For BDV check of transformer oil, shall we need to consider the oil temp? As mentioned in the above posting "Higher oil temperature causes higher equilibrium moisture in oil for same moisture in paper" and if temp drops, again insulation will absorb the moisture from transformer oil.
Advanced thanks...
RE: Oxygen in Transformer oil
Values by EPRI shows a surface moisture of 1.25 %.Normally in new transformers manufacturers try to limit to less than 0.8 %.ABB transformer installtion manuals give a graph connecting moisture content vs insulation temp vs dew point.
Dew point measurement will only give surface moisture content and may not reflect the actual moisture inside the insulation structure.
USBR graphs have been modified several times and the latest that one can refer to is fig A3 as given in IEC TS 60076-14 Technical Specifications for Design &Application of liquid immersed trfs using high temp insulation materials.Limitations of these graphs are given in IEEE draft std PC 57.106 D6.
A generation of enginners used Alnor, but today much better meters are available (eg Vaishala)for dew point measurement.
To the question how moisture content in paper of a working trf can be found- answer,very difficult,may be impossible.But many solutins are tried but with its own limitations.Latest in the field is PDC measurement ie measurement of polarisation and depolarisation current under a small DC voltage and then use computer models to estimate water content in paper.
electric pete- do you remember the nuclear trf you mentioned was with membrane (bag)inside the conservator or not?or N2 sealed.USBR maintenance manual (page 52 &53) gives some indication of CO2 values in oil and how leaks can afffect it.
BDV of oil will not change with temperature.It is more affected by particle content and to some extent by moisture content.Moisture content in working trf will vary with temperature,but it can vary only say 5-40 ppm.