Sea Marconi recently intervened to treat a transformer in a hydro-electric production plant in the north of Portugal, owned by EDP (Energias de Portugal), one of the largest producers of energy in Europe and one of the most important industrial groups in Portugal. The brilliant results of this activity earned Sea Marconi formal qualification by EDP (Labelec) for the “regeneration” of insulating oil in electrical transformers.
On a more operational level, the transformer treated is from 1953, with a power of 7.5 MVA, a voltage of 70 KV and an oil quantity of 6,300 kg. The activity performed on the transformer was necessary due to the presence of the criticality “corrosive sulphur from DBDS – C1“. The main indicators of the criticality encountered were the content of DBDS in the oil, specifically 76 mg/kg, and the CCD test, which proved corrosive.
Sea Marconi resolved the criticality through a DBDS Selective Depolarisation intervention, a form of dialysis on the transformer. In essence, thanks to the use of modular plants (DMU) constructed by Sea Marconi, the oil is cyclically extracted from the transformer, decontaminated inside the DMU using patented reactants, and once again pumped into the transformer in improved conditions. In this way, the transformer is never emptied of its oil load, and thanks to the constant flow of oil inside the transformer box, the latter benefits from a “cleaning” on the surface of the insulation and on the base of the box.
The Sea Marconi Selective Depolarisation treatment developed in Portugal, which lasted from 25th June to 2nd July 2015, was executed on-load, or rather with the transformer in service and under load for the entire duration of the activity.
The client followed all phases of the treatment, and through its laboratory (Labelec) re-analysed the oil at the end of the treatment. Specifically, it was noted that the DBDS passed to<5 mg/kg, the CCD test became “non-corrosive” and all other parameters were compliant with the IEC 60422 standard.
The results surprised and completely satisfied EDP, who as mentioned earlier, formally qualified the Sea Marconi process for the “regeneration” of insulating oil in electrical transformers.
