Failure mapping and critical measurements for the operating condition assessment of power transformers

The causes of failure of critical component of the electrical power distribution network like the power transformers, has always attracted the interest of the scientific and technical community, since the failures of electrical transformers almost always have a great impact on the consumers, as they can lead to a black out situation. A reliable and coherent maintenance schedule, that would predict the causes and prevent un-expectable shutdowns of power transformers, is of outmost importance nowadays, since electrification is expanding in terms of volume and power, as well as in terms of production sources, voltage and location. Such a reliable and coherent maintenance schedule depends on many factors and this article describes the parts of oil-immersed power transformers that are prone to failure. It also illustrates the relationship of the well known dissolved gasses that appear in the insulating oil as a result of specific operating faults, with specific measurements that should be done periodically, in order to prevent a major failure. Additionally, it describes the relationship between these dissolved gases with specific maintenance actions that should be implemented during the preventive maintenance process.