According to TABLE IV not all of the necessary data are available for every, transformer. There are only 34,2% (average) and 64,3% (maximum) of the necessary data available at the same time. The availability of the data effects the changing of reliability level. The reliability factor (TSIRi) decreases when missing either of the physical effects. The volume of decreasing is directly proportional to the weighting (Kj) of the effect [4].