In order to be transmitted to high-voltage lines and distributed, the electricity generated by nuclear power plants must be matched to the grid voltage. To achieve this, power transformers are installed on each unit. Given the electrical power involved, it is necessary to evacuate thermal losses, generally by means of the oil bath in which the magnetic circuit and winding are immersed. The oil is then circulated, either mechanically (pump) or by natural convection.
Electrical transformers in nuclear power plants generate a great quantity of heat. It is necessary to evacuate this heat flux by cooling to avoid hot spots that would weaken or damage the structure.
The aim of the study is to model oil circulation and determine the maximum temperatures reached: if a hot spot is identified, corrective solutions are proposed and validated by simulation to eliminate the risk.
We conduct thermal-hydraulic calculations of oil flow in transformers operating at the end of nuclear power plants. Thanks to these calculations, we are able to pinpoint the critical zones to be cooled, which must be optimized and then monitored to ensure optimum transformer operation, and guarantee the integrity and durability of the equipment.
CFD simulation was used in this case to test the influence of inlet temperature, flow rate and the physical properties of the oil on the occurrence, position and intensity of hot spots.
