Dissolved Gas Analysis (DGA) is a very effective transformer condition monitoring technique, especially in detecting potential internal damage long before failure occurs. One of the internationally recognized guidelines for interpreting DGA results is IEC 60599, issued by the International Electrotechnical Commission.
This article will discuss the basics of DGA interpretation according to IEC 60599, and how this standard is used to identify the types of faults in oil-based transformers.
Why is DGA Important?
Transformer oil not only functions as a coolant, but also as an insulator. When a thermal or electrical fault occurs, this oil will decompose and produce dissolved gases. The composition and concentration of these gases are analyzed using the DGA method to identify the type of failure.
Main Gases in DGA
Here are some of the main gases monitored in DGA:
- Hydrogen (H2)
- Methane (CH4)
- Ethylene (C2H4)
- Ethene (C2H8)
- Acetylene (C2H2)
- Carbon monoxide (CO)
- Carbon dioxide (CO2)
Each gas is associated with a specific type of disturbance, such as overheating, corona (partial discharge), or arcing.
Basic Principles of Interpretation Based on IEC 60599
IEC 60599 presents an interpretation method with two main approaches:
1. Comparison of Gas Concentrations
This standard provides gas concentration limits based on the severity of the disturbance, ranging from normal to critical conditions. Interpretation is done by comparing the gas value from the test results with the threshold.
2. Gas Ratio
In certain cases, the ratio between two or more gases is used to identify the type of disturbance. For example:
CH4 / H2 → indication of oil heating
C2H2 / C2H4 → indication of arcing
C2H6 / C2H4 → indication of mild overheating
This ratio helps to identify the type of damage such as partial discharge, arcing, overheating of oil, and overheating of insulating paper.
Fault Categories According to IEC 60599
Based on gas patterns and ratios, IEC 60599 groups faults into several categories:
- D1 (Partial discharge)
- D2 (Large discharge / arcing)
- T1 (Slight overheating)
- T2 (Moderate overheating)
- T3 (Severe overheating)
Thermal fault involving cellulose (indication of degradation of insulating paper)
DGA Interpretation Steps Based on IEC 60599
1. Take and analyze oil samples from the transformer
2. Identify dissolved gas concentrations
3. Compare gas concentration values ??with IEC 60599 thresholds
4. Use gas ratios to determine the type of fault
5. Classify severity and follow-up
IEC 60599 provides systematic and experience-based technical guidance for interpreting DGA results. By understanding the basics, maintenance teams can more quickly recognize transformer problems and take preventive measures before greater damage occurs.
Understanding this standard is not only important for engineers and technicians, but also becomes part of a reliable predictive maintenance strategy in the electrical sector.
Please contact the Hyprowira Laboratory providing Dissolved Gas Analysis (DGA) services, for more information.
