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Transformer oil analysis is one of the most effective methods for transformer condition control, early diagnosis and prevention.

In a desire to offer the full range of analyzes combined with a professional interpretation of results, assessment of the state of the transformers and subsequent recommendations, CERB united its efforts with the independent laboratory ICLab, Athens, Greece.

CERB Laboratory is accredited according to BDS EN ISO 17025: 2006, Registration No.225 LE of EA BAS with scope of accreditation - sampling and testing of transformer oils on the following tests or parameters:

• Density at 20° C (gr / mL)
• Breakdown voltage (kV)
• Water content (mgH2O / kgoil)
• Flash Point (° C)
• Acid Number (mg KOH / g oil)
• Water-soluble acids and bases detection
• Dielectric Dissipation Factor at 90 °C (tanδ).
• Resistivity (GΩ.m)

Transformer insulation system is a combination of liquid (transformer oil) and solid (cellulosic) insulation. Monitoring and maintenance of oil quality are essential to ensure the reliable operation of oil-filled electrical equipment. In order to evaluate the state of liquid isolation in transformers, a number of analyzes are performed: physico-chemical analysis, gas chromatography analysis, furanc compounds, corrosive sulfur, inhibitors, polychlorinated biphenyls (PCBs), infrared spectrum analysis, etc.

Under normal operating conditions and good maintenance practices the insulating oil retains its properties and structure resulting in good insulation, effective cooling of the active part maintaining a “healthy” environment for all the materials and operations in the transformer. In case of abnormal electrical or thermal influences, the oil may begin to decompose resulting in the formation of gases. The character kind, amount and rate of increase of the individual gases found in the oil are indicative of the type and the severity of defect in the installation equipment as well as the emergency for decisions and maintenance actions. The timely detection of dissolved gases in the oil and the correct interpretation of the results can prevent accidents and costly repairs.
The good condition of solid insulation of transformers is also of great importance for their normal operation. Furanic compounds dissolved in the oil are a specific products derived from the thermal chemical destruction of cellulose. These compounds serve as an indicator of the degree of aging of the insulation. Based on the results of a complex of laboratory analysis of transformer oil, our laboratory can diagnose emerging defects in the transformers at a very early stage and offer concrete recommendations for follow-up.