Primary alluminiun factory: 8 Rectifier Transformers (Sweden)

Nameplate data of transformers:

Manufact: xxx
Year: 1930
Power [MVA]: 19
Voltage [KV]: 13
Oil Mass [Kg]: 15.000
Oil type: mineral blended


Selective depolarization treatment (Chedcos) in order to remove the DBDS + dehalogenation treatment (CDP Process) in orderr to remove the PCBs both from oil and transformers. The treatments were performed on-site, on-line and on-load (transformer in servise and under charge during the treatment).

The treatments were carried out with the following guarantees: DBDS < 10 mg/kg, PCBs < 2 mg/Kg restoring also the other oil parameters as suggested by IEC 60422 ed. 4, 2013

Before the treatments

After the treatments

PCBs [mg/Kg] 29 0,37
DBDS [mg/Kg] 18 < 5
IFT [mN/m] 24 42
CCD Test corrosive NOT corrosive
TAN [mg KOH/g] 0,34 0,01
DF 0,230 0,002
Dehalogenated and depolarizated transformers

Identified Critical issues

Applied solutions

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