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.

I. Introduction

INSULATION oil-paper system is the core of power transformer [1], among which mineral insulation oil has been used for more than 120 years because of its excellent insulation performance, oxidation stability and low viscosity [2]. With the proposed demand for high fire resistance of insulating oil and the implementation of the two-carbon policy, researchers conducted a long-term study on the replacement of oil products by mineral insulating oil, mainly focusing on synthetic ester, natural ester and mixed insulating oil [3].