A particular analysis about the first three energization failures of poleⅠ high voltage converter transformer at Fulong station during initial stage of the third phase commissioning of Xiang-Shang±800 kV ultra-high voltage direct current（UHVDC） transmission project is presented. Based on the function and operation principle of valve base electronics（VBE）， switching philosophy of valve cooling system， and inrush current produced when energizing the transformer， a study on energization failure is completed. It is concluded that high inrush current and weak sending terminal， which causes distortion of bus-bar AC voltage， result in a valve fault erratically detected by the VBE， and valve cooling systems switching over abnormally so as to trip the transformer. Some suggestions based on the conclusion are proposed for solving these problems， which can also provide certain technical reference for normal operation of existing and coming projects.