Abstract
A Duval triangle is a diagram used for fault type identification in dissolved-gas analysis of oil-filled high-voltage transformers and other electrical apparatus. The proportional concentrations of three fault gases (such as methane, ethylene, and acetylene) are used as coordinates to plot a point in an equilateral triangle and identify the fault zone in which it is located. Each point in the triangle corresponds to a unique combination of gas proportions. Diagnostic pentagons published by Duval and others seek to emulate the triangles while incorporating five fault gases instead of three. Unfortunately the mapping of five gas proportions to a point inside a two-dimensional pentagon is many-to-one; consequently, dissimilar combinations of gas proportions are mapped to the same point in the pentagon, resulting in mis-diagnosis. One solution is to replace the pentagon with a four-dimensional simplex, a direct generalization of the Duval triangle. In a comparison using cases confirmed by inspection, the simplex outperformed three ratio methods, Duval triangle 1, and two pentagons.
Highlights
IntroductionThe classic Duval triangle [1], shown in Figure 1, uses concentrations (absolute or incremental) of methane, ethylene, and acetylene dissolved in the insulating oil of a transformer to locate a point in the interior of an equilateral triangle that has been subdivided into fault zones corresponding to the six basic International Electrotechnical Commission (IEC) fault types (see Table 1) plus a mixture DT of electrical discharge and thermal
The classic Duval triangle [1], shown in Figure 1, uses concentrations of methane, ethylene, and acetylene dissolved in the insulating oil of a transformer to locate a point in the interior of an equilateral triangle that has been subdivided into fault zones corresponding to the six basic International Electrotechnical Commission (IEC) fault types plus a mixture DT
The original Duval triangle is very effective, it has been supplemented with two more Duval triangles–one (Triangle 4) based on hydrogen, methane, and ethane, and the other (Triangle 5) based on methane, ethane, and ethylene–to produce more refined fault type identification using hydrogen and all four of the low molecular weight hydrocarbon gases, generated from transformer oil by high temperatures and electrical discharges, that are commonly used for dissolved-gas analysis (DGA) [4]
Summary
The classic Duval triangle [1], shown in Figure 1, uses concentrations (absolute or incremental) of methane, ethylene, and acetylene dissolved in the insulating oil of a transformer to locate a point in the interior of an equilateral triangle that has been subdivided into fault zones corresponding to the six basic International Electrotechnical Commission (IEC) fault types (see Table 1) plus a mixture DT of electrical discharge and thermal. The DGA 4-simplex is a direct generalization of the Duval triangle, it differs from the triangle in interesting respects such as how four-dimensional fault zones are defined and how the geometric fault type classification can be visualized Three gas ratio methods, Duval triangle 1, Duval pentagon 1, the Mansour pentagon, and the DGA 4-simplex are compared in Section 9 by applying them to 629 cases of transformer faults confirmed by inspection. This paper, relates only to diagnostics for mineral-oil-filled transformers
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