A dry-type electrical transformer includes a coil assembly having at least one winding wound into a plurality of concentric turns, at least one cooling sector defined between adjacent concentric turns, spacers positioned inside the cooling sector and spaced from each other to allow a plurality of air ducts each defined between two adjacent spacers, and at least one electrical shield positioned in the cooling sector and arranged to electrically shield the air ducts. At least one electrical shield is positioned in the cooling sector and arranged to electrically shield the air ducts. The electrical shield include a first end edge connected to the turn at the inner side of the cooling sector, a second end edge which is free and electrically insulated from the surrounding parts, and a central portion extending between the first and second end edges and is positioned at the outer side of the spacers.