Early detected transformers incipient faults by means of physical-chemical diagnostics

This paper describes seven cases of operating HV transformers with early incipient fault, detected during the performance of regular preventive diagnostics of about 400 large HV transformers in Slovenia during the last 17 years. All seven faulty transformers were discovered by means of GC dissolved gas in oil analysis or/and HPLC Furanics in oil analysis. Among them one especially interesting case is presented of very early detection of an anomaly in an almost new transformer. All cases are described by presenting the historical record of results of diagnostic tests, the diagnosis we arrived at, as well as findings after internal inspection of opened transformer in a transformer factor. The contact person from transformers owner for each of the described cases, who can confirm our statements, is named.