A century of dissolved gas analysis - part III

With time, the size of the transformer increased exponentially both in power andvoltage. Although huge improvements have been made regarding the magnetic core and the decrease of core losses, a transformer is now producing much more heat due to the design optimization and size reduction. Heat reduces the insulating properties of the insulating matrix, reducing the conducting properties and accelerating all chemical reactions including ageing and corrosion. The stresses from the insulation materials increase gradually. In the last century, the ratio of oil volume to the transformer power decreased substantially, and concomitant with this trend, the transformer power and voltage increased. This means less cooling and less insulation for each MVA and kV. The transformer’s efficiency increased as well, mainly due to the development of new core material alloys. Also, the thickness of the core plates gives assistance in reducing no-load losses