Transformer Load Loss Levels

Hi, could anyone assist me with the following. I am carrying out calculations on a transformer and it is required for me to state what the load loss and no-load loss levels are. the choices are A0, AA0 & AAA0 for no load loss level and Ak, Bk & Ck for the load loss levels. Apparently, they have something to do with the IEC 60076 standards but i am unable to find the relevant reference for them.

Furthermore, i require assistance in determining the maximum HV and LV insulation levels. would they be located on the transformer technical sheet, are they some standard or calculation ? (N.B. the only options are <=24 kV or 36 kV for HV and <=1.1 kV or >1.1 kV for LV)