环保型气体绝缘变压器中使用C4F7N/氦气混合气体的可行性研究：介电强度与散热性能

This contribution proposes an eco-friendly insulation gas mixture of perfluoroisobutyronitrile (C4F7N)/helium with good heat transfer performance for gas-insulated transformers (GITs). The dielectric strength of C4F7N/helium was assessed by AC breakdown test and voltage withstand test. The heat dissipation performance of the mixture was evaluated by test of temperature rise due to short-circuit on a self-cooling GIT. The test results demonstrated that the dielectric strength of C4F7N/helium exhibited a synergistic effect in various proportions. Especially for 40% C4F7N /60% helium, its dielectric strength could exceed that of SF6 used in existing GITs. After filling it into the eco-friendly GIT, the dielectric strength remains stable and the average temperature rise of the winding could be reduced by over 20% . In addition, based on the convection heat dissipation model, a calculation method for the average temperature rise of the eco-friendly GIT was adjusted. The errors of the model were found to be within a margin of ±3°C for C4F7N/helium under different pressures and proportions. The dielectric strength and heat dissipation performance of the mixture indicated that 40% C4F7N /60% helium could directly replace SF6 without adjusting voltage levels or insulation gaps in larger capacity and eco-friendly GITs.