Improvement in Efficiency of Converter Transformer by The Reduction of Stray Losses

In High Voltage Direct Current Transmission (HVDC) system, converter transformer (CT) is an essential part of the system. Losses that occur in the CT are copper loss, stray loss, and core loss. The stray loss occurs in the transformer's metallic parts, such as transformer tank, which is 10% to 15% of the total loss. Current flowing through the CT is non-sinusoidal current, so more losses are produced in the CT than normal power transformer.  In this paper, horizontal wall shunt is used to reduce stray loss in CT and compare the performance with vertical wall shunt. These stray losses calculated using the 3-D finite –element analysis (FEA). A 315 MVA CT is considered as a case study to calculate stray losses with and without wall shunt. Results show that the horizontal wall shunt is effective compared to vertical wall shunt; additionally, the stray loss is reduced as the wall shunt thickness is increased. Therefore, the efficiency of CT is increased due to a decrease in stray loss.