Notice, there is no area on the triangle for a transformer that does not have a problem. Picture 2: L1 Limits and Generation Rate Per Month LimitsĬAUTION: Do not use the Duval Triangle ( Picture 1) to determine whether or not a transformer has a problem. Draw lines across the triangle for each gas, parallel to the hash marks shown on each side of the triangle. Plot the percentage of each gas on the Duval Triangle, beginning on the side indicated for that particular gas. This gives the percentage of increase of each gas of the total increase.ĥ. Divide each individual gas difference by the total difference of gas obtained in step 3 above. This gives 100 % of the three key gases, generated since the fault, used in the Duval Triangle.Ĥ. Add the three numbers (differences) obtained by the process of step 2 above. Repeat this process for the remaining two gases, ethylene and acetylene.ģ. This will give the amount of methane generated since the problem started. Take the amount (ppm) of methane in the DGA and subtract the amount of CH 4 from an earlier DGA, before the sudden increase in gas. Detailed instructions and an example are shown below. Subtracting out the amount of gas generated prior to the sudden increase will give the amount of gases generated since the fault began. Also, calculate the amount of the three gases used in the Duval Triangle, generated since the sudden increase in gas began. Once a problem has been determined to exist, use the total accumulated amount of the three Duval Triangle gases and plot the percentages of the total on the triangle to arrive at a diagnosis. If there is a sudden increase in H2 with only carbon monoxide and carbon dioxide and little or none of the hydrocarbon gases, we need to determine if the cellulose insulation is being degraded by overheating.Ģ. The L1 limits and gas generation rates from table on Picture 2 are more reliable than the IEEE® method however, one should use both methods to confirm that a problem exists. To use this table without the IEEE® method, at least one of the individual gases must be at L1 level or above and the gas generation rate must be at least at G2. At least one of the hydrocarbon gases or hydrogen must be in IEEE® Condition 3 and increasing at a generation rate (G2), from table shown on Picture 2, before a problem is confirmed. First determine whether a problem exists by using the IEEE® method above, and/or table shown on Picture 2 below.

Duval triangle calculator