Insulation condition assessment of power transformer bushings by utilizing high voltage lightning impulses

High voltage bushing forms an essential part of a power transformer and its insulation condition is of high importance in a transformer's reliability. Transformer failure statistics indicate considerable contribution from bushing failures, which makes the monitoring of power transformer bushings essential. Several off-line and on-line methods are available for condition assessment of these components. However, most of the on-line methods cannot provide as much information as off-line methods because of the performance limitations. Therefore, condition assessments of these components are mostly done through several on-line methods and decision-making must be done according to majority agreements between different techniques. This paper investigates the possibility of assessing the insulation condition of power transformer bushing through utilizing high voltage transients. They are used as stimuli to get the dielectric response of the insulation system. The investigation is done on two service-aged 150 kV power transformer bushings. The results are verified by comparison with Frequency Domain Spectroscopy (FDS). The proposed application seems promising for monitoring of dielectric properties of power transformer bushings.