Usability of vibration measurement for power transformer diagnosis and monitoring

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.