Transformer diagnostics
Oil Services & Dissolved Gas Analysis
Transformer oil sampling, testing, and dissolved gas analysis — the most sensitive diagnostic tool available for detecting developing faults inside oil-filled transformers before they cause failures.
What Your Transformer Oil Is Telling You
Transformer oil serves two critical functions: it insulates the transformer's internal components and it dissipates heat generated by the core and windings. As a transformer ages and experiences electrical and thermal stress, the oil and the solid insulation inside the tank degrade — and that degradation produces gases. Dissolved gas analysis (DGA) measures the concentration of these gases in the oil to identify what type of fault is occurring, how severe it is, and how quickly it is progressing.
DGA is widely recognized as the most sensitive and cost-effective diagnostic tool for oil-filled transformers. A single oil sample, analyzed correctly, can reveal thermal faults, partial discharge, arcing, and insulation degradation that would be completely invisible to any external inspection. J. Wesley Services Group performs oil sampling and coordinates laboratory analysis, then interprets the results in the context of the transformer's service history and operating conditions.
Key Gases and What They Indicate
Hydrogen (H₂)
Produced by partial discharge (corona) activity and low-energy electrical faults. Elevated hydrogen is often the first indicator of developing electrical stress in the insulation system.
Methane (CH₄) & Ethane (C₂H₆)
Generated by low-temperature thermal faults (overheating of oil). Elevated levels indicate hot spots in the oil that may be caused by overloading, blocked cooling, or circulating currents.
Ethylene (C₂H₄)
Produced by higher-temperature thermal faults. Significant ethylene generation indicates oil temperatures above normal operating range, often associated with core or winding hot spots.
Acetylene (C₂H₂)
Generated by high-energy electrical arcing. Even small concentrations of acetylene are a serious indicator of arcing faults inside the transformer and warrant immediate investigation.
Carbon Monoxide (CO) & Carbon Dioxide (CO₂)
Produced by degradation of the solid cellulose insulation (paper and pressboard). Elevated CO and CO₂ indicate thermal or electrical stress on the solid insulation, which is not self-healing and represents permanent insulation loss.
Oxygen (O₂) & Nitrogen (N₂)
Monitored as indicators of oil oxidation and the integrity of the transformer's sealing system. Elevated oxygen suggests oil oxidation or air ingress, both of which accelerate insulation aging.
Oil Testing Services We Provide
- Oil sampling from in-service transformers (live-line sampling)
- Dissolved gas analysis (DGA) with laboratory coordination
- Interpretation and reporting using IEEE C57.104 and IEC 60599 guidelines
- Moisture content (Karl Fischer) testing
- Dielectric breakdown voltage testing
- Acid number and interfacial tension testing
- Color and visual inspection
- Trending and historical comparison across multiple sample intervals