Scenario
4 GSU transformer at thermal power plant
Nameplate data of the transformers:
Manufact: xxx
Year: 1997
Power [MVA]: 192
Voltage [KV]: 400
Oil mass [Kg]: 58.000
Oil type: naphthenic
May 2005
The analysis and subsequent diagnosis performed by Sea Marconi on the equipment of the customer showed:
Index of corrosiveness =1 (max level)
ASTM b 48H= 4C
Overall Health index: 0.52 (52%)
April 15, 2006
Failure caused by discharges of high energy
April 19, 2006
Internal inspection and post failure analysis performed by Sea Marconi experts
November 2006 – Solution
Solution: Selective depolarization treatment (Chedcos) by Sea Marconi performed on the twins transformers.
he treatment guaranteed DBDS < 10 mg/kg and at the same time the restoring of the other parameters according the IEC 60422 ed. 4, 2013
Before treatment |
After treatment |
|
| DBDS [mg/Kg] | 110 | < 5 |
| IFT [mN/m] | 17 | 40 |
| TAN [mg KOH/g] | 0,133 | < 0,01 |
| DF | 0,0448 | 0,0118 |
