Abstract
In the paper a thorough electromagnetic transient analysis of a combined instrument transformer will be given. A CAD procedure for transformer optimal design by using a genetic algorithm original program will be accomplished. The transient analysis will be fulfilled for the initial and optimal design as well as for a realised transformer prototype. The transient analysis will be non-linear, since the results from previous FEM-3D electromagnetic field study as well as the non-linearity of the two transformer measurement cores will be incorporated.