The subject of the invention is an electric power switchgear, an insulating radiator, and a method for installing the radiator in an electric power switchgear, and in particular in a medium or high voltage switchgear. The electric power switchgear comprising working elements placed in the housing and connected with busbars and branches, and cooled with air, is characterized in that it contains at least one insulating radiator made of thermoplastic material of increased thermal conductivity λ≧2 W/mK, which is placed in the electric field of the switchgear and which is connected by a non-permanent fastening to at least one busbar or/and at least one branch. The insulating radiator designed for the switchgear is an injection molding including a base plate to whose top face a system of heat evacuating elements of identical or diverse shape is attached, and to its side surfaces elastic assembly catches are fixed.