On Site Oscillating Lightning Impulse Test and Insulation Diagnose for Power Transformers

Abstract

This letter proposed a new lightning impulse test method for power transformers based on oscillating lightning impulse(OLI) waveform. The OLI has high generation efficiency and is easy to generate for field test. Partial discharge detection and transfer function analysis are used to evaluate the transformer insulation condition during the impulse test. The OLI waveform for transformer test satisfied with the requirements of the standard is obtained by altering the value of resistance and inductance in the circuit. The experiment was carried out on a transformer scale model to prove the validity of the proposed method. The results show that the current pulse method and the UHF method detect the PDs simultaneously as the insulation defect is excited at high voltage. Meanwhile, the transfer function changes due to the discharge in winding. It provides a new test and insulation diagnose method with application prospects for transformer lightning impulse test on site.