For insulating fluids that have acidity and polar compounds, Sea Marconi has developed a service called selective depolarisation from acidity (Chedcos®) aimed at the elimination of the polar compounds and products of oxidation responsible for the increase of total acidity (TAN) and Dielectric Dissipation Factor, and the simultaneous improvement of the chemical, physical and dielectric properties of mineral insulating oil in line with IEC EN CEI 60422 Ed. 4, 2012.

This solution avoids the operational problems of changing the fluid, which would still be contaminated by acidic and polar contaminants from the oil residue from impregnated pressboards.

The service includes the following activities:

• Two-way transport of personnel, technological systems, equipment and supplies from Sea Marconi to the location sites of transformers;
• Hydraulic and electrical installation and connection of mobile depolarisation units (MDUs)
• Deosvision® analysis before treatment (if any);
• Selective depolarisation treatment (Chedcos®);
• Physical decontamination treatment (degassing and dehydration under vacuum);
• Monitoring of treatment parameters;
• Replacement of oil of variator under load (if any);
• Checking levels and vents;
• Replacement of dryer salts with silica gel;
• Deosvision® analysis at end of intervention
• Oil inhibition with antioxidant additive DBPC (potential) should the initial conditions of the oil be such as to arouse suspicion that the oil has lost resistance to oxidation

Chedcos® selective depolarisation from acidity is cheap and effective, because it guarantees total acidity < 0,05 mgKOH/> and the Tan delta dielectric dissipation factor at 90 °C < 0,1 nonché il ripristino delle altre proprietà funzionali in conformità alle norme IEC 60422 Ed. 4 2013 e CIGRE 378 art. 4.2.pan>