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This paper discusses the use of vibrations for power transformer surveillance. Therefore, basic research of transformer vibration is presented including the physical background of vibrations and methods of measurement in terms of sensor techniques comparing in-oil and outside tank wall measurement. A case study of an outside tank wall measurement performed on an aged generator step-up transformer presents first experiences in terms of long term measurement evaluating data of a 2-years period. A use case for vibration measurement is drawn for direct current (DC) detection in power transformers. DC can couple into 3 phase AC systems from nearby HVDC systems. The core's subsequent static magnetic field leads to increased core power losses and higher stress for the entire transformer. [ABSTRACT FROM PUBLISHER]

The paper presents a long-term monitoring example of an aged generator step-up transformer with several PD sources showing different activity. Monitoring data is recorded by the use of the electromagnetic PD measurement method, also known as the UHF-method. The phase resolved PD patterns of collected UHF measuring data are analyzed using cross-correlation. The method searches for characteristics of a typical pattern called template. PRPD patterns of the entire dataset are evaluated. The result is the time dependent occurrence of a specific pattern, respectively a specific PD source. [ABSTRACT FROM PUBLISHER]

The paper presents a comparison of gas solubility of different mineral oils as well as ester-based transformer insulating fluids. The maximum gas solubility of different gases, e.g. ambient air, nitrogen or fault gas is determined. Also, the solubility of a gas mixture in transformer oil is analysed. In addition, the experimental values are compared to calculated values derived from engineering standards. [ABSTRACT FROM PUBLISHER]