17 years of monitoring on 8 industrial transformers (43,5 MVA), for a primary aluminum company.
DGA values much higher than typical values defined by IEC 60599, kept under control with periodical oil treatment, and frequent OLTC repairing.
With this kind of control those equipment are working at 100% loading and more since many years, without failures.
The same monitoring has been done on oil properties and oil degradation rate.
DDF slow increase has been obtained with periodical oil treatment and filtration, to reduce sludge and deposits accumulation.
The increase of acidity (not influence by oil treatment) is kept under control and did not need corrective action until now.
