In order to investigate the reasons of fault offen occurs in the transformer often presents during the preventative test
such as exceeding rated value of the direct current resistance imbalance rate and generating heat of bushing coupler
the elimination method and the infrared technology of measuring temperature are adopted.Based on test data
the main inducement of defect is the coupler loses contact with the conductor rod in the transformer bushing type BRLW-110/630.The defects of the coupler are analyzed