Lightning Breakdown Macroscopic Behavior Analysis of Three-element Mixed Insulation Oil-Paper System

The breakdown voltage (BVE) of insulation oil-paper system is crucial to the steady operation of transformer. In this paper, the voltage and current waveform, BVE, discharge development time of mineral oil-paper system (MO-P) and three-element mixed insulation oil-paper system (TEMO-P) at gap lengths of 0, 5, 10 and 15 mm, as well as the morphologies of oil-impregnating paperboard are studied. The results show that under negative polarity, the increase of BVE with gap of TEMO-P has more obvious advantages than MO-P. Under positive and negative polarity, the rapid rise zones of MO-P discharge development time are different, ranging from 10 mm to 15 mm and from 0 mm to 10 mm respectively. Both positive and negative polarity of TEMO-P increased at 5 mm to 15 mm. After the breakdown under negative polarity, the surface of TEMO-P is prone to large area dendritic.