Positive and Negative Polarity Lightning Impulse Breakdown Characteristics for Multi-Element Mixed Insulating Oil

The multi-element mixed insulating oil (MEMO) as an alternative liquid has been developed to support the reliable and safe operation of high-voltage and large-capacity power transformers. However, lightning impulse breakdown characteristics have always been a key challenge restricting the reliability of high-voltage power transformer insulation. Thus, this work focuses on the investigation analysis of lightning impulse discharge characteristics for the MEMO. The results show that the lightning impulse breakdown voltage of MEMO is slightly lower than that of MO under positive and negative polarities. However, the breakdown voltage of MEMO under long oil gaps can reach the same level as that of traditional MO. At long oil gaps, the MEMO was only 77.29 %, 82. 32 %, and 8 3. 2 8 % of MO at failure probabilities of 1 %, 63.2 %, and 90%. This research provides a theoretical reference for the MEMO application to high-voltage and large-capacity oil-immersed power transformers.