The Importance of Bushing Connections in Transformers

This study addresses the overheating issues that cause the low-voltage (LV) busbars of transformers to become discolored due to excessive heating, as well as the solutions to these issues. Transformers are essential for efficiently transmitting electrical energy over long distances by converting it from low voltage to high voltage or vice versa. The installation and connection of transformers in the field require various electrical and mechanical connections. Errors in these connections and installation processes can lead to electrical leaks, short circuits, and even system failures. The aim of this study is to identify the root cause of the discoloration of the low-voltage busbars in the transformer, which is due to excessive heating caused by incorrect connections made by the customer in the field. It was found that the resistance values of the overheated LV bushings were high, and abnormal increases were observed in the resistance values between phases. It was concluded that the discoloration due to overheating could be related to issues in the connections between the high-resistance points of the transformer terminals and the bushing components. Additionally, short-circuit tests and thermal imaging studies related to the overheating of the bushings helped better understand the underlying causes of the problem.As a result of the analysis, phase-to-phase winding resistances were balanced, and it was determined that the problem originated from the installation of the low-voltage bushings. Damaged terminals and gaskets were replaced, loose connections were tightened, and appropriate torque values were applied. Using the 8D analysis method, the root causes of the issue were systematically identified, and permanent solutions were developed. These solutions were successfully implemented and tested in the field, ensuring the transformers operated more safely and efficiently.