Produced within a power range between 1OkVA - 100MVA, up to 154kV high voltage level three phase or single phase, oil immersed, ONAN, ONAF, OFWF, with Off-Load or Dn-Load Tap Changer, used both external and internal Dimensions of transformer conservator are determined and designed after several heat calculations of the oil stored in expansion tank and oil level changes by heal Being open to atmosphere, oil pressure changes continuously in Conservator Type Transformers due to thermal effects and exchange of air is dehumidified via air breather silicagel.