Transformer TX-101 in the demonstration fleet: ethylene and acetylene both high. How the analyzer separates a hot spot from tap-changer contamination, and why the methods disagree.
| Transformer | TX-101, 132/33 kV, 40 MVA, ONAF, conservator, communicating on-load tap changer, built 2009 |
| Latest sample (ppm) | H2 50, CH4 150, C2H6 50, C2H4 270, C2H2 120, CO 380, CO2 3 200 |
| Trend | TDCG 349 → 433 → 593 → 1 020 ppm; four gassing events open |
| Ratio | Value |
|---|---|
| C2H2/C2H4 | 120/270 = 0.44 |
| CH4/H2 | 150/50 = 3.0 |
| C2H4/C2H6 | 270/50 = 5.4 |
Arcing in the diverter switch produces acetylene with little hydrogen. Oil leaking into the main tank adds acetylene that has nothing to do with the main tank's condition.
Ethylene (270 ppm) and C2H4/C2H6 = 5.4 point to a hot spot above 700 °C in the main tank; the acetylene may come partly from the OLTC. The analyzer reports T3 (38 %), DT (26 %), C (17 %), D2 (16 %) and IEEE Status 3.
| Check | Requirement | Actual | Status |
|---|---|---|---|
| IEC 60599 Table 1 | Match a fault row | No match (mixed) | ✗ FAIL |
| Duval Pentagon 1 | Zone | T3 | ✗ FAIL |
| OLTC contamination (C2H2/H2) | < 2 | 2.4 | ✗ FAIL |
| IEEE C57.104 status | Status 1 | Status 3 — Extreme | ✗ FAIL |
Key insight: When methods disagree, check for contamination before diagnosing. On units with a communicating OLTC, C2H2/H2 above 2 in the main tank is a strong sign that some of the gas is not from the main tank.
Every input in this example is editable in the live calculator — no signup needed.
Open DGA Analyzer (Transformer Oil) calculator →The pentagon uses five gases including H2 and C2H6, so it separates thermal faults better; the triangle uses only CH4, C2H4 and C2H2 and is pulled towards D by the acetylene.
The tap changer of TX-101, entered as its own asset. Comparing its DGA with the main tank is how OLTC contamination is confirmed.