DIN 42508-4

Transformers; three-phase oil immersed transformers with off-circuit tap-changer or with on-load tap-changer, 12500 to 80000 kVA for 50 Hz and U<(Index)m> 123 kV; main dimensions and weights for 25000 to 40000 kVA

Deutsches Institut Fur Normung E.V. (German National Standard) , 05/01/1993