Symptoms (analysis)
Due to intimate contact with the papers, insulating oil becomes a vector of symptomatic indicators of the criticality. Through oil analysis it is therefore possible to identify and quantify the total sludge.
The specific symptom of the “Insoluble deposits (sludge)” criticality is related to the presence in oil of the following diagnostic indicators with non-conforming typical values:
Sludge indicators derived from degradation of oil
Sediments and sludge (Annex C of IEC 60422 Ed. 4-2013)
Water in oil (IEC 60814)
TAN Acidity (IEC 62021-1)
Dissipation factor (IEC 60247)
Interfacial tension (ASTM D971, EN 14210)
Particles (IEC 60970)
Sludge indicators derived from degradation of paper
Oxygen
CO2 – carbon dioxide
CO – carbon oxide
2FAL – 2furaldehyde and other furan compounds
Methanol
Ethanol
Symptomatic hot spot gases (methane, ethane, ethylene)
There are also co-factors useful to complete the diagnostic framework (resulting from the oil analysis):
Additives:Passivators (BTA, Irgamet 39, Irgamet 30); Oxidation inhibitors (DBPC, DBP)
DBDS (IEC 62697-1)
Dissolved metals (ASTM D 7151)
Oxidation stability (IEC 61125)
Oil fingerprint
Using oil analysis
it is possible to estimate the amount of total sludge in the transformer