Insulation Breakdown Failure Analysis of a 500kV Power Transformer in Lightning Impulse Test

By applying artificial simulated lightning wave to transformer winding terminals, lightning impulse test could investigate impact strength of transformer main insulation and series insulation. We studied an insulation breakdown failure case of a 500kV transformer during its lighting impulse test in factory and analyzed main factors of the insulation breakdown failure. Insulator quality and insulation design related to the flawed components were discussed. This paper could provide some guidance in regarding to improving supply quality of transformer components and avoiding similar insulation weakness.