A cooling system for a high voltage electromagnetic induction device includes: at least one duct filled with a first coolant and surrounded by a second coolant, each being routed along a direction ofnatural convection; at least one group of fans, each fan of the group being mounted along a respective duct of the at least one duct along the direction of natural convection and being configured to blow for the-second-coolant-forced cooling; at least one group of electric motors, each electric motor being configured to operate a respective fan of the at least one group of fans; at least one groupof switches, each switch being configured to control a respective electric motor of the at least one group of electric motors. A method of cooling a high voltage electromagnetic induction device is also provided. By using the option of operating fans with higher cooling rate and because of the less fans are operating, the predetermined cooling capacity can be reached with lower power consumption.