Physical-chemical oil tests, monitoring and diagnostics of oil-filled transformers

This paper presents physical-chemical testing methods as used today worldwide and at the Institute Chemistry Department. Investigation results obtained by means of various physical-chemical tests of transformer oil samples provide not only the liquid dielectrics quality; they also enable diagnosis of the current operational capability, estimating reliability and assessment of the residual technical lifetime of power, instrument and furnace transformers. Findings based on experimental research and experience of the Institute´s Chemistry Department in the furanic-in-oil HPLC analysis of transformers in service are presented. They enable diagnosis of the degradation degree of paper insulation in oil-filled paper-insulated HV transformers. This paper advises HV transformer owners or supervisors which oil tests should be made to get the right or expected information about transformers in their different lifetime situations. Various Institute programs in compliance with which transformer preventive diagnostics are being pursued are discussed. The described efforts laid in practicing regular preventive diagnostics have enabled appropriate transformer maintenance whenever practicable. This means that transformers are serviced in time, efficiently and at the minimum cost, thus providing the basis for their reliable long-term operation.