ategorizing Faults via DGA GE Grid Solutions M&D
First, What Is Transformer Dissolved Gas Analysis? Sample Test Doc Diagnosis Doctors extract information about our health from our blood. Technicians extract information about the health of our transformers from the oil via DGA. Substations are more challenging for this sampling process than a doctor s office.
Transformer Dissolved Gas Analysis, The Process & Logic Duvall s Triangle Sample Test Tech Diagnosis We prefer a clean sample with no issues detected, just as a blood test in a doctor s office.
Transformer onstruction Bushings Tap changer ooling System oils Oil Tank ontrol abinet ore
What Are The Relevant Gases? Paper & Oil Gases ot Metal Gases
6 Oil degradation Typical oil Molecule
Knowing Industry Standards & Their Intended Use Dissolved key gas concentration ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; limits - IEEE 57.14 2 4 22 24 26 O O2 TDG ondition 1 1 12 1 5 65 35 25 72 ondition 2 11-7 121-4 2-9 51-1 66-1 351-57 2,5-4, 721-1,92 ondition 3 71-1,8 41-1, 1-35 11-2 11-15 571-1,4 4,1-1,1,921-4,63 ondition 4 >1,8 >1, >35 >2 >15 >1,4 >1, >4,63 ondition 1 ondition 2 ondition 3 ondition 4 TDG below this level indicates satisfactory operation. Any individual combustible gas exceeding specified levels should prompt additional investigation. TDG within this range indicates greater than normal combustible gas level. Any individual combustible gas exceeding specified levels should prompt additional investigation. Action should be taken to establish a trend. Fault (s) may be present. TDG within this range indicates a high level of decomposition. Any individual combustible gas exceeding specified levels should prompt additional investigation. Immediate action should be taken to establish a trend. Fault (s) are probably present. TDG within this range indicates excessive decomposition. ontinued operation could result in failure of the transformer.
Understanding Duval s Triangle, Fault odes.
IEEE 57.14 Key Gases Evaluation Arcing in Oil Partial Discharge in Oil 6% 5% 4% 3% 2% O 2 4 26 24 1% 8% 6% 4% O 2 4 26 24 1% 22 2% 22 % % Overheated Oil Overheated ellulose 7% 6% 5% 4% 3% 2% 1% O 2 4 26 24 22 1% 8% 6% 4% 2% O 2 4 26 24 22 % %
Ratios for key gases Doernenburg Ratios for key gases Doernenburg Suggested fault diagnosis Ratio 1 (R1) 4/2 Oil Gas space Ratio 2 (R2) 22/24 Oil Gas space Ratio 3 (R3) 22/4 Oil Gas space Ratio 4 (R4) 26/22 Oil Gas space 1. Thermal decomposition >1. >.1 <.75 <1. <.3 <.1 >.4 >.2 2. Partial discharge (low-intensity PD) <.1 <.1 Not significant <.3 <.1 >.4 >.2 3. Arcing (high-intensity PD) >.1 to <1. >.1 to <.1 >.75 >1. >.3 >.1 <.4 <.2
Rogers Ratios For Key Gases Rogers ratios for key gases ase R2 22/24 R1 4/2 R5 24/26 Suggested fault diagnosis <.1 >.1 to <1. <1. Unit normal 1 <.1 <.1 <1. Low-energy density arcing Pd a 2.1 to 3..1 to 1. >3. Arcing igh-energy discharge 3 <.1 >.1 to <1. 1. to 3. Low temperature thermal 4 <.1 >1. 1. to 3. Thermal <7 5 <.1 >1. >3. Thermal >7 a There will be a tendency for the ratios R2 and R5 to increase to a ratio above 3 as the discharge develops in intensity.
Transformer Operating Temperatures 2 8? First signs of gassing begins around 1 with O2 & O. First signs of hot metal gases begins around 15.
Diagnosing Transformer Main Tank Faults
Where s The Problem? Nitrogen Sealed #1 36 MVA Nitrogen Sealed #2 3 MVA 4% 4% 3% 3% 2% 2% 1% 1% % 2 4 26 24 22 % 2 4 26 24 22 12 1 O2/O Ratio 7 6 O2/O Ratio 8 6 4 2 Pre Event Post Event 5 4 3 2 1 Pre Event Post Event
Where s The Problem? ontinued Winding Failure #1 Primary Lead Repairable #2 Transformer Replaced Transformer Repaired
O2/O Ratio Experiment 9 8 7 6 O2/O RATIO 5 4 3 oil flash paper 2 1 test1 test2 test3 test4 test5 test6 tes 7 test8 test9 test1
Where s The Problem? DATE 2 O2 N2 4 O O2 26 24 22 TDG O2/O 11/4/29 235 12,771 68,988 686 277 2,879 228 1,523 52 31 1.3935 1/8/21 268 14,477 81,77 986 369 4,63 323 2,196 54 4,238 11.184 2/23/21 282 13,893 76,571 821 312 4,56 329 2,239 47 4,3 14.44231 3/22/21 272 13,34 71,225 834 284 3,2 32 1,892 33 3,617 11.26761 5/6/21 226 11,639 68,938 974 35 4, 325 2,54 39 3,968 11.42857 8/13/21 134 11,897 59,148 1,138 298 3,451 337 2,358 14 4,279 11.5854 1/12/211 329 8,613 72,536 1,663 577 5,183 447 3,215 14 6,245 8.982669 1/25/211 256 9,233 67,438 1,151 491 4,979 421 2,443 16 4,778 1.1453 16 O2/O 2% Decline Overall 3,5 24 38% Increase Overall 14 12 1 8 6 4 O2/O Linear (O2/O) 3, 2,5 2, 1,5 1, DET oked 24 Linear (24 ) 2 5 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9
Descending O2/O Ratios - 75 MVA, N2 Blanketed M DATE 2 O2 4 O O2 26 22 24 O2/O 3-Jul- 12 ND 9715 1 64 453 ND ND ND 7 6-Jul-11 ND 118 1 22 485 2 ND 1 22 25-Jan- 1 ND 5893 1 17 439 2 ND 2 26 9-Mar-9 ND 1738 TRAE 4 475 1 ND TRAE 118 26-Mar- 8 ND 2829 1 25 851 2 ND 3 34 15-Feb- 7 ND 1667 TRAE 22 816 1 ND 3 37 O2/O 14 12 1 8 6 4 81% Drop in 5 Years O2/O Linear (O2/O) 2 27 28 29 21 211 212
15 MVA, 1 kv Manufactured 1999 Pre-Fault M Date 2 O2 O2 O 4 26 24 22 O2/O 211 <2 845 579 8 5 6 2 <1 72.3 <2 831 524 5 2 4 1 <1 14.8 212 213 <2 59 226 3 1 <1 <1 <1 75.3 214 <2 192 178 6 1 <1 <1 <1 29.6 215 <2 5 124 1 2 1 <1 <1 12.4 14 12 1 8 6 4 2 O2/O 1 2 3 4 5 6 O2/O Linear (O2/O) 8 7 6 5 4 3 2 1 O2/O Ratio 211 215 83% Drop 211 215
1999, 15 MVA, 1 kv, omplete Picture Date 2 O2 O2 O 4 26 24 22 O2/O 211 <2 845 579 8 5 6 2 <1 72.3 212 <2 831 524 5 2 4 1 <1 14.8 213 <2 59 226 3 1 <1 <1 <1 75.3 214 <2 192 178 6 1 <1 <1 <1 29.6 215 <2 5 124 1 2 1 <1 <1 12.4 216 post fault 212 82 1188 414 21 72 372 422 2.8 14 12 O2/O 96% Drop 211-216 8 7 O2/O Ratio 1 6 8 6 4 2 O2/O Linear (O2/O) 5 4 3 2 1 211 216 1 2 3 4 5 6 211 216
1 MVA Mobile Transformer Test Date ydrogen Methane Ethane Ethylene Acetylene O2 O O2/O Nitrogen Oxygen 9/5/22 2 182 221 8.235294 68476 9186 8/19/24 4 o 1875 249 7.5312 861 7268 6/16/25 2 1 1951 231 8.445887 7914 7284 8/14/26 6 3 345 322 1.71429 829 757 8/7/28 2119 736 44 666 145 253 239 1.58577 67189 7881 9/18/28 296 937 48 954 1888 3475 298 11.6617 8536 1146 25 14 O2/O DET Failed 2 15 1 5 2 4 26 24 22 1 2 3 4 5 12 1 8 6 4 2 29% Increase Overall O2/O Linear (O2/O) 1 2 3 4 5 1 2 3 4 5 6
115-4kV, MVA Rating 18/24/33.6 Test Date ydrogen Methane Ethane Ethylene Acetylene O2 O O2/O Nitrogen Oxygen 2/19/213 2 12 14 17 2118 61 34.72 77642 242 8/1/213 2 7 12 13 1776 53 33.51 84976 1819 7/31/214 2 5 11 5 66 24 27.5 78121 27 9/21/215 3 5 1 2 355 64 5.55 6955 159 11/29/216 344 24 35 494 57 4 72 5.56 7881 O2/O 6 5. 4. 3. O2/O 5 4 3 1 2 3 2. 1. Linear (O2/O) 2 1 4 5. 1 2 3 4 5 1 2 3 4 5 4 3 2 1 O2/O Ratio 211 216 84% Drop 213-215 211 216
Analyzing Events via O2/O 25 2 15 1 5 O O 22 21 2 19 18 17 O2 O2 12 1 8 6 4 2 26 26 28 29 21 211 213 28 29 21 211 213 28 29 21 211 213 O2/O Ratio 12 1 8 2136 ppm 21 ppm 6 4 211 213 Failed the following year, 214 2 185 ppm 2 ppm 211 213
Finding The Problem 2 2 >5 2 4 >55 2 6 >7 4 >293 O 2 <25 O<5 Gassing began in 21 12 1 8 6 4 2-2 36 MVA Nitrogen Blanket 1999 25 213 O2:O Linear (O2:O)
Finding The Problem, ontinued Long history of gassing including acetylene and high levels of ethylene. Due to high combustible gas levels and the increasing O 2 :O ratio, problem was narrowed down to overheating occurring on either the DET or primary/secondary leads. Primary lead was found bare against a corona shield. It was re-taped and in subsequent DGA tests there has been no production of combustible gas.
Do I ave ealthy Paper? Are There Indicators Within DGA? M Date 2 4 26 24 22 O2 O O2 O2/O June-12 ND 2 1 1 ND 282 14 157 2 Nov-13 ND 3 4 ND ND 566 15 139 38 Sept-14 ND 3 ND ND ND 466 11 8712 42 July-15 1 3 2 ND ND 313 5 9141 63 7 O2/O RATIO 63 6 5 4 3 2 1 2 38 42 O2/O RATIO 212 213 214 215
Acetylene Is Problematic, But Is It Fatal? Not always: Is it present due to activity in the winding insulation, or is it bare metal? The problem could be easy to get to and simple to repair. Transformers have been discarded when the problem was a simple fix, but that was unknown at the time. It can mean the difference between a few thousand dollar$ in repairs, versus a few million dollar$ in potential replacement costs.
Effects Of Thumping Faults With A Power Transformer Sampled right after main tank fault. Notice the arcing signature in the main tank.
Effects Of Thumping Faults With A Power Transformer, ontinued 6% 5% 4% 3% 2% 1% % Main Tank Arcing Effects of Thumping Faults w/power Transformer 2 4 26 24 22 2 4 26 24 22 % Gas Generation hart -Arcing in Oil kkkkkkkkkkkkkkkkkk Reference: IEEE Std 57.14-28 kk 6% 5% 4% 3% 2% 1% % 2 4 26 24 22 2 4 26 24 22 2 O2/O Ratio 15 1 Pre-Fault Ratio Post Fault Ratio 5
Summary/onclusion All internal faults are not fatal. Know your fleet. It will be beneficial in solving the diagnostic puzzles as they present themselves. All faults are not as easily identified. Don t give up, as there is an answer. Allow software to help with the data analysis and direct you to the critical assets and information, which are now available. Trending the fluctuations of gas concentration, rate of change and ratios is very important for understanding your transformers vital signs. Know when to reach out for additional support, if needed. We are all in this together.