Thermographic analysis of power oil transformer surface hot spot areas combined with analysis of acoustic signals recorded on line

The paper presents the results of thermographic and acoustic analysis of exemplary oil power transformer. Series of thermograms were taken. The higher temperature areas were distinguished on the transformer surfaces under different ambient temperatures. The thermograms indicated hot areas at the top of the transformer, especially under high ambient temperature. There were three areas that emit intensive infrared radiation in the spectrum: 7.5 μm < λ< 13 μm. These areas are located in the upper part of the transformer in zones of intense oil circulation forced by the cooling system. According to thermographic research the state of the transformer and the cooling system was proper. Within acoustic research, two areas were located with sources of magnetoacoustic signals of increased activity with the spectrum 15-65 kHz. Sources of these signals were intense phenomena occurring during the magnetization of ferromagnetic materials. No acoustic emission signal with increased activity from partial discharges were detected. The result of thermographic analysis corresponds with the results of acoustic signals analysis and analyzed together give a broader common description of the examined phenomena.