Nameplate data of transformer:

Transformer: grid transformer
Manufact: xxx
Year: 1957
Power [MVA]: 50
Voltage [KV]: 225
Oil Mass [Kg]: 38.000
Oil type: blended mineral oil

Transformer contaminated by PCBs and corrosive sulfur compounds


Selective depolarization treatment (Chedcos) in order to remove corrosive sulfur compounds and dehalogenation treatment (CDP Process®) in order to remove the PCBs from oil and transformer. The treatment was performerd on-site and on-load (transformer in operation and fully load during the treatment).

Before the treatments

After the treatments Sea Marconi

PCB* [mg/Kg] 81 20
Total sulfur [mg/Kg] 21,600 20,500
TCS (total corrosive sulfur)
as DBDS Eq. [mg/Kg]
140 < 10
CCD Corrosive NOT Corrosive
DBTP [mg/Kg] 380 280
TAN [mg KOH/g] 0,096 < 0,03
IFT 19,5 26
Color 6,9 3

*The agreed guarantee was PCBs < 40 [mg/Kg]

Identified Critical issues

Applied solutions

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