Dissolved Gas Analysis (DGA) of Transformer Oil
Probability Norms (90%) (ANSI / IEEE C57.104-1991) for mineral oil filled transformers
Gas | Symbol | Normal Content | Generating Conditions (excess) |
Key combustible Gases | |||
ACETYLENE | C2H2 | 35 ppm | High Energy Arcing |
HYDROGEN |
H2 |
100 ppm | Corona (Partial (Discharge) Electrolysis of Free Water Arcing (If Acetylene is also present) |
METHANE | CH4 | 120 ppm | Generalized Overheating |
ETHANE | C2H6 | 65 ppm | Generalized Overheating |
ETHYLENE | C2H4 | 10 ppm | Hot Spot Severe Localized Overheating |
CARBON MONOXIDE | CO | 350 ppm | Aging/Thermal Decomposition of Cellulose |
Non combustible Gases | |||
NITROGEN |
N | Less than 5% of total | Normal Operation |
Greater than 5% | Check for tightness of Nitrogen Seal | ||
CARBON DIOXIDE: Check Ratio of CO2/CO |
CO2 CO | Ratio less than 7 - | Cellulose Breakdown |
Ratio greater that 7 | Normal | ||
CO > 500 CO2 > 500 | To improve certainty factor | ||