Acetylene in transformer insulation oil
Acetylene in transformer insulation oil
(OP)
Guys,
We have in our plant a 230 /13,8 kV 31 MVA transformer that had the following DGA result (in ppm):
H2: 228
O2:15400
N2:74000
CH4:41
CO: 297
CO2:1570
C2H4:64
C2H6:9
C2H2:179
Total:818
After this result, we did the ultrasonic test to locate some partial discharge inside the equipment. The result indicated that might have been some problens around the OLTC. So, we decided to call the OLTC manufacturer to do a full inspection at the OLTC.
They found some loose conection between the switch and tap windings. We repaired these connections and we treated the insulating oil to remove the gas dissolved. Then we put the tranformer to operate again. In the latest DGA, we notice that acetylene level is rising again.
My question is: Is it possible that some acetylene was trapped in the transformer paper and insulation and now they are being released or there are another problem inside the transformer?
I am attaching the loose concections picture.
Thanks
We have in our plant a 230 /13,8 kV 31 MVA transformer that had the following DGA result (in ppm):
H2: 228
O2:15400
N2:74000
CH4:41
CO: 297
CO2:1570
C2H4:64
C2H6:9
C2H2:179
Total:818
After this result, we did the ultrasonic test to locate some partial discharge inside the equipment. The result indicated that might have been some problens around the OLTC. So, we decided to call the OLTC manufacturer to do a full inspection at the OLTC.
They found some loose conection between the switch and tap windings. We repaired these connections and we treated the insulating oil to remove the gas dissolved. Then we put the tranformer to operate again. In the latest DGA, we notice that acetylene level is rising again.
My question is: Is it possible that some acetylene was trapped in the transformer paper and insulation and now they are being released or there are another problem inside the transformer?
I am attaching the loose concections picture.
Thanks






RE: Acetylene in transformer insulation oil
RE: Acetylene in transformer insulation oil
RE: Acetylene in transformer insulation oil
RE: Acetylene in transformer insulation oil
The most recent DGA: (08/17/2016)
H2: 5
O2:14100
N2:45400
CH4:3
CO:32
CO2:410
C2H4:2
C2H6:6
C2H2:13
Total:61
The first DGA after re-energization (05/07/2016)
H2: 2
O2:4000
N2:13700
CH4:0
CO:0
CO2:230
C2H4:1
C2H6:0
C2H2:0
Total:3
The second DGA after re-energization (05/11/2016)
H2:3
O2:17700
N2:58100
CH4:0
CO:33
CO2:460
C2H4:2
C2H6:1
C2H2:5
Total:44
The third DGA after re-energization (05/31/2016)
H2:5
O2:9600
N2:30900
CH4:0
CO:25
CO2:280
C2H4:1
C2H6:0
C2H2:6
Total:37
The fourth DGA after re-energization (06/29/2016)
H2:6
O2:7700
N2:21600
CH4:0
CO:19
CO2:260
C2H4:1
C2H6:0
C2H2:9
Total:35
RE: Acetylene in transformer insulation oil
RE: Acetylene in transformer insulation oil
Assume that transformer was vacuumed before filling with oil. Current C2H2 level is high (condition 3 as per C57.104-2008) and require prompt additional investigation. Monitor the gas increase. Looks like an arcing (without involving paper) somewhere, may be benign. It can be a loose current carrying contact or equi-potentional connection creating floating potential or core frame grounding at more than one point. Have you checked core grounding? What is the loading level of transformer? Get help from OEM, quite tricky to locate the point of arcing. I had faced quite a few such problems from transformers in service and required long investigation to locate and eliminate the trouble point..
RE: Acetylene in transformer insulation oil
RE: Acetylene in transformer insulation oil
RE: Acetylene in transformer insulation oil
RE: Acetylene in transformer insulation oil
RE: Acetylene in transformer insulation oil
RE: Acetylene in transformer insulation oil
I have received the latest DGA results. These analysis was made by a different laboratory from the previous ones.
NOV first 2016
(ppm)
H2:9
O2:38200
N2:113500
CH4:3
CO:72
CO2:1030
C2H4:3
C2H6:0
C2H2:32
Total:119
NOV eleven 2016
(ppm)
H2:10
O2:38700
N2:112100
CH4:3
CO:81
CO2:1070
C2H4:3
C2H6:0
C2H2:35
Total:132
RE: Acetylene in transformer insulation oil
I'm pondering now why there may be differences in opinions/experiences. One thing may be the type of transformer and type of processing. My experience was primarily 600MVA 345kv GSU transformers with conservators. They have lots of thick insulation in there so maybe more likely to retain residual oil containing gases (?). And we had various imperfect methods for determining endpoint of processesing such as isolating the transformer and checking the equilibrium pressure/dew point reached. But it was not a perfect system, and there were schedule pressures. We often saw our moisture in oil results shoot back up to 15 or 20 or sometimes 25ppm at about 70C oil temperature within a month of putting the transformer back in service, which is one indicator of incomplete processesing with respect to moisture trapped in the paper. Another indicator: when we finally added a cold trap as part of our processing, we realized that there was still a lot of water coming out in the cold trap long after we would have stopped processing by our older procedures. All this tells me that some of our processing attempts were certainly incomplete with respect to water. Maybe this "incomplete processing" with respect to water might also have some correlation with respect to amount of residual oil and trapped gases? I realize the mechanism for storage within insulation is different for water (absorbed directly in cellulose insulation) and gases (trapped in oil within insulation), but maybe it's plausible anyway? Beats me.
If it is plausible, it might be interesting to know the water results for this transformer before and after and also details about whether it is conservator or nitrogen blanketed.
=====================================
(2B)+(2B)' ?
RE: Acetylene in transformer insulation oil
But cellulose will not trap any gas but only oil -that is my learning so far.The latest results show the problem is continuing and my judgement remains the same.
RE: Acetylene in transformer insulation oil
RE: Acetylene in transformer insulation oil
RE: Acetylene in transformer insulation oil
RE: Acetylene in transformer insulation oil