Investigation of failure of high voltage bushing at power transformer

In this paper, bushing-breakdown was identified as one of the main causes of transformer failure that resulted in a fire outbreak in July 2015 at the Gadong Power Station, Brunei Darussalam. To perform the investigation, three specimens from the burnt pieces were collected, which were white ash, bushing housing ashes and solid remnants from the burnt site. Both JSM-610F FIELD Emission Scanning Electron Microscope (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) were used to obtain the electron images, and to analyze the types of elements present in the specimens. In addition, software simulations for the high voltage bushing failure were carried out using COMSOL Multiphysics Software for different oil levels, and the obtained results have been summarized. Finally, it is comprehended that fire outbreak happened due to leaking of the insulating oil in the high voltage bushing and loose tighten of the sealing part of the cable termination boxes.