PURPOSE: To reduce cooling area of a cooler needed for cooling an insulating gas and achieve a compact design by connecting an insulating inner container which is installed within a tank of the main unit of an equipment and a liquid cooler which is installed outside the tank at a pipe path for circulating an insulating liquid and by constituting one part of a circulating pipe path of that insulating liquid as an indirect heat exchanger of a gas cooling body which is filled into the tank of the main unit of the equipment.

CONSTITUTION: A core 3 and a winding 4 generate heat while using an electrical equipment and an insulating liquid within an insulating inner container 2 and an insulating gas within a tank 1 are heated. The insulating liquid thus heated circulates within an insulating liquid circulation pipe path 7 and is cooled by a liquid cooler 5. At the same time, the cooled insulating liquid is circulated within an insulating gas cooling part 8 consisting of a branch pipe path 9, a cooling panel 10, and a branch pipe path 11, thus cooling the insulating gas at a high-temperature part which is located at the upper part within the tank 1. With this system, since the cooling panel 10 cooling the insulating gas within the tank 1 is a heat exchanger of liquid and gas, cooling efficiency of internal insulating gas can be improved as compared with the conventional heat exchange system with gas.