- It is recommended that strategic information be updated through a “dynamic inventory” of oils and transformers, indicating the values of symptomatic markers.
- It is recommended that maintenance practices be changed:
- buying new mineral oils compliant with IEC 60296, or natural ester oils compliant with IEC 62770, or synthetic ester oils compliant with IEC 61099 or silicone oils compliant with IEC 60836.It is advisable to select the oils by comparing products for the intended applications (contact us for the support)
- checking the oils in the acceptance phase of supplies according to the prescribed methods
- requiring that the factory tests are conducted using oils free of degradation compounds and monitoring, also in subsequent phases of the life cycle, that the treatments on the oil and transformer are not a source of cross-contamination
- From an asset management point of view it is recommended acting preventively with a depolarisation treatment against acidity and not wait for the oil to reach the thresholds specified in IEC 60422 (critical acidity if > 0.15, > 0.20, > 0.30 mgKOH/g depending on the different categories of transformers); in fact, an acidity between 0.07 and 0.10 mgKOH/g has already shown phenomena of corrosion by dissolved metals (C4), dangerous sludge formations with negative effects on insulating papers.
What are the prevention actions to be taken on electrical equipment with insulating liquids other than mineral ones?
Concerning natural ester oils and synthetic esters, the prevention actions are the same, but it is advisable to choose countermeasures after careful assessment of cost-benefit, cost-effectiveness and environmental impact (biodegradability and fire safety). For silicone oils in operation, the treatments recommended by the standard (IEC 60944:1988) are “vacuum treatment and filtration” and “molecular sieves and filtration”.