The invention is an electric insulation system for a steel-structured lid of an electric arc furnace, where the electrode lead-throughs are provided with electric insulation for preventing breakdowns, and the lid is sealed from the furnace vessel by means of a sand seal. The lid is divided by steel-structured panels to at least six mutually electrically insulated segments, three of which form thelid center part, so that each center part segment outlines one lead-through of an electrode (102), and at least three of which form the outer perimeter of the lid.