With the rise of renewable energy resources, especially offshore wind power plant, the DC transmission concept has attracted more and more attention. The selection of eco-friendly insulating gas, as most critical insulating part of gas-insulated equipment is top priority for developing highly reliable system. Moreover, it is acknowledged that eco-friendly C₃F₇CN/CO₂ gas mixtures have become a potential alternative to SF₆ gas due to its excellent performance. This study reviews the basic physical properties of C₃F₇CN gas/gas mixtures and insulation properties including the gas gap breakdown and surface flashover performance at DC, as well as lightning impulse voltage. Investigation about the gas stability is presented, including the compatibility of gas with solid materials in gas-insulated transmission line (GIL), and the decomposition characteristics under long-term electrical and thermal stresses. The important progress on the charge accumulation characteristics of gas–solid interface in the novel gas environment under DC voltage stress is analysed. Finally, the key issues that need to be paid attention to and further followed through regarding the application of this novel gas in GIL are summarised and put forward. This study hopefully can provide a complete reference for the development of eco-friendly DC gas insulation equipment with C₃F₇CN/CO₂ gas mixtures.

随着可再生能源尤其是海上风力发电厂的兴起，直流输电概念越来越受到人们的关注。选择环保型绝缘气体作为气体绝缘设备最关键的绝缘部分是开发高度可靠的系统的当务之急。此外，公认的是，环保的C ₃ F ₇ CN / CO ₂气体混合物由于其出色的性能已成为SF ₆气体的潜在替代品。这项研究回顾了C ₃ F ₇的基本物理性质CN气体/气体混合物和绝缘性能，包括气隙击穿和直流下的表面闪络性能，以及雷电冲击电压。提出了关于气体稳定性的研究，包括气体与气体绝缘传输线（GIL）中的固体材料的相容性以及长期电应力和热应力下的分解特性。分析了新型气体环境下直流电压应力下气固界面电荷积累特性的重要进展。最后，总结并提出了有关这种新型气体在GIL中的应用需要注意和进一步遵循的关键问题。这项研究有望为使用C的环保型DC气体绝缘设备的开发提供完整的参考。₃ F ₇ CN / CO ₂气体混合物。