Abstract: Tank for electrical transformer comprising a bottom plate, two side panels and two end panels joined to contain an insulating fluid, and reinforcements joined to the exterior of said panels, wherein the two side panels and the two end panels are vertically curving convex panels, wherein the reinforcements comprise a plurality of arched vertical reinforcements distributed horizontally along each panel. The reinforcements may comprise a plurality of bracing horizontal reinforcements joined between said vertical reinforcements. The inner arching profile of the vertical reinforcements preferably matches the outer curving convex profile of the panels. The horizontal reinforcements are preferably planar. The horizontal reinforcements are preferably located at a horizontal plane in the vertical middle of the respective panel. The horizontal reinforcements are preferably located at a middle horizontal plane or at parallel horizontal planes distributed vertically.