Determination of the optimum position and size of the magnetic shunts in the tank wall of the power transformer

An effective method of reducing losses due to stray fluxes in the tank walls of power transformers is the use of magnetic shunts. Magnetic shunts direct stray fluxes towards themselves and prevent them from reaching the tank. Transformer manufacturers commonly use vertical magnetic shunts on the inner surface of tank walls to reduce tank loss. In this thesis, the optimum use of horizontal shunt in a power transformer was investigated. For this purpose, firstly, a 50 MVA power transformer manufactured by the transformer manufacturer using optimized vertical magnetic shunts on the tank wall was analyzed for 100 ms at full load. The tank loss values obtained as a result of the analysis were verified with experimental results and the validity of the model was proven. Tank loss samples were taken by analyzing for 2 milliseconds when vertical magnetic shunts were present only on the long front wall and only on the short side wall of the transformer tank. Based on the tank loss samples of the transformer with vertical magnetic shunts, parametric analyses based on the finite element method were performed for 2 milliseconds using horizontal magnetic shunts only on the short side wall and only on the long front wall of the tank. As a result of the parametric analyses, a tank model with horizontal magnetic shunts with suitable location and size was obtained. The optimum position and size of the horizontal magnetic shunt tank was modeled and the transformer was analyzed at full load for 100 milliseconds and compared with the experimental and simulation results of the vertical magnetic shunt transformer manufactured by the transformer manufacturer. According to the results obtained, a saving of 25.83% is achieved in the horizontal magnetic shunt volume compared to the vertical magnetic shunt volume. It has been found that the maximum magnetic flux density in horizontal magnetic shunts and the maximum current density in the transformer tank with horizontal magnetic shunt are lower than the vertical. The effects of magnetic shunts on the tank and core in the event of a three-phase-to-ground short circuit while the transformer is operating at full load were investigated. In the three phase-ground short circuit event, the cases where there is no magnetic shunt on the tank wall, where there is a vertical magnetic shunt and where there is a horizontal magnetic shunt obtained with optimum placement are examined separately. It has been determined that in a three phase-to-ground short circuit event, the highest loss occurs in the tank without a magnetic shunt, and the lowest loss occurs in the tank with a vertical magnetic shunt. It was determined that the maximum current density in the horizontal magnetic shunt transformer tank in the three phase-to-ground short circuit event was lower than that in the vertical magnetic shunt transformer tank. The highest current density in the tank occurred in the transformer without a magnetic shunt on the tank wall. The effects of one phase-to-ground, two phase-to-ground and three phase-to-ground short circuit events on the transformer tank loss and core loss are also investigated. The highest tank loss, lowest core loss and maximum current density on the tank occurred in the three phase-to-ground short circuit events.