Question 1

Which method is right when the figures disagree?

Accepted Answer

The question has no published answer, and this page does not invent one. CIGRE TB 771:2019 App. H.6 (printed p. 70) treats a disagreement between Triangles 1, 4, 5 and Pentagons 1, 2 for the same DGA results as a finding in its own right — multiple faults may be suspected — because each graphical representation is more sensitive to some gases and some faults than to others. So the disagreement is information about the equipment, not a defect in the tools, and fusing the verdicts into one would destroy it. No figure is ranked above another here, and no combined confidence number is computed.

Question 2

Why is Triangle 4 or Triangle 5 sometimes shown as "not applied"?

Accepted Answer

Because the published sequence does not license it for that sample. Triangle 4 follows a Triangle 1 identification of PD, T1 or T2; Triangle 5 follows T2 or T3. After a Triangle 1 result of D1 or D2 — low- and high-energy discharges — CIGRE TB 771:2019 App. H.2 (printed pp. 67–68) says Triangle 4 should not be used and Triangle 5 used only with caution: the zones drawn on Triangle 4 are PD, S, C and O, and on Triangle 5 PD, S, C, O, T2 and T3, so applying either to a D1 or D2 point would force a thermal or a PD label onto a discharge fault. The row says which Triangle 1 result withheld the figure rather than leaving the figure out.

Question 3

What does "shown outside the published sequence" mean?

Accepted Answer

It marks a figure that the sequence does not license but that is shown anyway, because the sample sits within analytical accuracy of a zone that does. It applies to one case only: a Triangle 1 point reported as D+T whose uncertainty region reaches T2 or T3. The accuracy figures are the IEC requirements quoted in CIGRE TB 771:2019 §2.2 (printed p. 13) — ±15 % above 10 ppm, ±30 % between 5 and 10 ppm. The construction is TriboTech’s, so any figure carried by it is labelled as lying outside the published sequence; presenting it as a step in the Duval sequence would be a misattribution. A reported D1 or D2 never gets this treatment, because App. H.2 speaks to those and says no.

Question 4

Why are Pentagons 1 and 2 not applied to an ester sample?

Accepted Answer

They are the mineral-oil figures. The ester fluids have their own published lineup — Triangle 3 (or 3b where the solid insulation is cellulose) with Pentagon 3 and Pentagon 4 or 4b — and the comparator applies that lineup instead. The mineral rows stay visible and state the reason, so a reader can see what was not applied and why rather than having to notice an absence.

Question 5

Why are Rogers, Doernenburg and Key Gas missing?

Accepted Answer

They belong to a separate reference tier and are deliberately not part of this comparison. They are not counted in the agreement statement, and no agreement or disagreement with them is reported. That is a scope decision, not an oversight.

Question 6

Why does the IEC 60599 row not count towards agreement?

Accepted Answer

Because App. H.6 does not name it. The clause lists Triangles 1, 4, 5 and Pentagons 1, 2, and IEC 60599 uses a different code vocabulary — its DT means "diagnosis tentative", not Duval’s mixed discharge-and-thermal zone. Comparing across the two would need a source saying they are comparable, and none is cited here. The IEC row is reported on its own terms instead. Note also that IEC 60599:2022 §6.1 c) (printed p. 17) states its gate as a conjunction of concentration and rate of gas increase; a single sample carries no rate, so only the concentration half is verified.

Method-agreement comparator

About the tools on tribotech.dk

Method-agreement comparator

About the tools on tribotech.dk