Duval’s Triangle 4 was developed to assist in the identification of low-energy faults to provide more information on the fault.

The three dissolved gases that make up Duval’s Triangle 4 are Hydrogen (H₂), Methane (CH₄), and Ethane (C₂H₆). This is arranged in a ternary plot similar to Duval’s Triangle 1 as depicted in Figure 1 below.

The fault regions are :

• PD – Corona or partial discharges
• O – Overheating is usually in the T1 (< 300 °C) region in Duvals Triangle 1
• C – Heating that may involve carbonization of cellulose for the T2 ( > 300°C) region in Duvals Triangle 1
• S – is a region that may indicate stray gassing

The one precondition is that Duval’s Triangle 4 can only be used after it has been identified by Duval’s Triangle 1 that the fault type is that of either PD, T1, or T2. It also cannot be used for the identification of faults of the D1 and D2 electrical fault types.

Analyze dissolved gas sample by entering values below in ppm.

Duvals Triangle 4

Hydrogen (H₂):

Methane (CH₄):

Ethane (C₂H6):

Plot

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

• Duval’s Triangle 1
• Duval’s Triangle 5
• LEDT
• Rogers Ratio Method
• Doernenburg’s Method
• Key Gas Method