Duval’s Triangle 5 is made up of three dissolved gases Methane (CH₄), Ethylene (C₂H₄), and Ethane (C₂H₆). This is arranged in a ternary plot similar to Duval’s Triangle 1 as depicted in Figure 1 below:

Duval’s Triangle 5 was developed to assist in the identification of medium to high-level energy faults to provide more information on thermal faults in paper and oil. These consist of faults such as

• PD – Partial Discharge
• T2 – Hotspots in oil ( > 300°C)
• T3 – Hot spots in oil (> 700°C)
• S – Stray Gassing
• O – Overheating
• C – Possible carbonization of paper C (in most cases)

Limitation: Duval’s Triangle 5 should be used only for faults identified first with Duval’s Triangle 1 as faults T2 or T3. It should never be used in case of electrical faults D1 or D2. It is also found that for faults O, S, and PD, Duval’s Triangle 4 must be used.

Enter oil samples in the Duval’s Triangle 5 tool below in ppm to test your sample.

Duvals Triangle 5

Methane (CH₄):

Ethylene (C₂H₄):

Ethane (C₂H6):

Plot

Other dissolved gas analysis methods that may be of interest are:

• Duval’s Triangle 1
• Duval’s Triangle 4
• LEDT
• Rogers Ratio Method
• Doernenburg’s Method
• Key Gas Method