Investigation of the Breakdown Mechanisms and Characteristics of 3.5%C4F7N/96.5%CO₂ Gas Mixtures Under Positive Lightning Impulse Voltage

a 3.5% C₄F₇N gas mixture will be proposed for multiple new high-voltage, eco-friendly devices, where the breakdown voltage under lightning impulses is a critical safety parameter. However, limited data exist on this specific ratio, and discharge simulation models must be validated experimentally to enhance device development efficiency. To address this gap, we performed plasma-based simulation modeling and experimental cross-verification of the 3.5%C₄F₇N/96.5%CO2 mixture. Our study elucidates streamer evolution in high-pressure environ-ments and clarifies the influence of pressure on discharge. The experimental breakdown voltage of this gas mixture exhibits increasing scatter with higher pressures; specifically, at 0.7 MPa, it rises by 57.6% compared with 0.5 MPa. Furthermore, the discrepancy between the numerically derived 50% lightning breakdown voltage and experimental results remains below 3%. This model can thus improve development efficiency and reduce testing costs for next-generation eco-friendly high-voltage equipment.