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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 indicators:

• Density at 20° C (gr / ml)
• Breakthrough voltage (kV)
• Moisture content (mgH2O / kgoil)
• Flashing temperature (oC)
• Acid KOH / g oil
• The presence of water-soluble acids and bases
• Dielectric loss coefficient at 90 ° C (tg δ)
• Specific Voltage Resistance (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, furan compounds, corrosive sulfur, inhibitors, polychlorinated biphenyls (PCBs), infrared spectrum analysis, etc.

Under normal operating conditions the insulating oil retains electrical and chemical stability. In case of abnormal electrical or thermal influences, the oil may begin to decompose resulting in the formation of gases. The character, amount and rate of increase of the individual gases found in the oil are indicative of the type of emergence defect in the installation. The timely detection of available gas in the oil and the correct interpretation of the results can prevent accidents and costly repairs.

The good state of solid insulation of transformers is also of great importance for their normal operation. Furane compounds dissolved in the oil are a specific product derived from the thermal chemical destruction of cellulose. These compounds serve as an indicator of the degree of aging of the insulation and can indirectly be inferred from the residual resource.

Based on the results of a complex of laboratory analysis of transformer oil, the Chemical Laboratory at CERB EAD can diagnose emerging defects in the transformers at a very early stage and offer concrete recommendations for follow-up.