Sampling Drift on Duval Triangle + Pentagon
See how a 5 mL air gap (V_G) shifts your DGA fingerprint across Duval Triangle 1 and Pentagon Unified zones. Each gas has its own Ostwald coefficient, so the same V_G removes a different fraction of each gas — that asymmetry is what pushes a fingerprint across a zone boundary.
If you haven't seen the syringe animation yet, start with the single-gas calculator.
See how a small air gap shifts your DGA fingerprint across Duval zones. Each gas has its own Ostwald coefficient, so the same V_G partitions each gas by a different fraction.
100 mL
5.0 mL |
Fingerprints: PD, D1, D2, T1, T2, T3, S, C — verified against IEC 60599:2022 Table 1, Duval & Lamarre (2014) IEEE EI Magazine 30(6), CIGRE TB 771 (2019), Paulhiac & Duval (2023) CIGRE ICTRAM06.
Triangle 1 — drift between true and measured
| Gas | True (dissolved in oil) | Measured (after headspace loss) | |
|---|---|---|---|
| H2 | 30.0 | 15.4 | -48.6% |
| CH4 | 200.0 | 178.1 | -10.9% |
| C2H2 | 1.0 | 1.0 | -4.1% |
| C2H4 | 180.0 | 175.0 | -2.8% |
| C2H6 | 60.0 | 58.9 | -1.8% |
Sources
- IEC 60567:2023 Annex A Table A.1 — Ostwald coefficients for fault gases in mineral oil.
- IEC 60599:2022 Table 1 + Fig B.3 — Duval Triangle 1 zone boundaries and fault typing for mineral oil.
- Paulhiac & Duval (2023), “Unified pentagon for DGA in mineral insulating oil”, CIGRE / Centre of Excellence for Transformers paper — Pentagon Unified consolidated zone set. Background: CIGRE TB 771 (2019), "Advances in DGA interpretation".
Related
- Headspace loss calculator (Step 1) — computes single-gas Ostwald loss without Duval interpretation.
- Blog: The physics behind correct oil sampling — full background on why V_G matters in the first place.
[VERIFICATION NEEDED] Fault fingerprints in the selector are placeholder values pending Erik’s verified briefing. Only T2 is a verified fingerprint (T2/T3 boundary case used in the blog narrative).