Distribution transformer impulse test — comments

The objective of the impulse tests on distribution transformers is to evaluate the winding insulation performance against lightning. Therefore, the acquired wave shapes must not present failure evidences. The key point on these cases is that some measurement equipments rarely show failure signals, mainly signals due to high frequency oscillation, considering as perfect a failed transformer. This paper discusses some mathematical model and testing results that shows that some high frequency oscillations are related to turn-to-turn failures.