628 / 2017-05-15 20:32:59

Investigations on the Breakdown Performances of Eco-friendly SF6 Alternative Gases

Breakdown performance,SF6 alternative gas,Gas pressure,Electrical equipment

SF6 is widely used in electrical equipment for its excellent properties of insulation and arc extinguishing, especially applied in high voltage switchgears. However, SF6 is a potent greenhouse gas, with the global warming potential of 23,500 compared to CO2. In order to reduce and replace the use of SF6, many different gases have been deeper investigated in the past years, such as N2, CO2, CF4, CF3I and their mixtures, and more investigations have being performed. Recently, it seems no suitable alternative gas was acceptable for generalization because of the shortcoming in each gas. In this paper, three eco-friendly SF6 alternative gases are investigated in the form of gas mixtures, including the modern concerned gases from 3M. The basic electrical insulating properties of these gases are acquired by setting up the experimental platform. The 50% breakdown voltage U50 of the three eco-friendly SF6 alternative gases are determined and compared. The results indicate that the dielectric strength of the SF6/N2 mixture decreases with the content decline of SF6. With the increasing of gas pressure, the breakdown voltage of the studied gases gives a rising tendency. For the C5F10O mixture, its concentration has to be chosen so low that the corresponding partial pressure is below the vapor pressure of the substance at the lowest temperature. Take the breakdown performance of the C5F10O mixture into account, the potential to replace SF6 in medium voltage equipment can be accepted. Similarly, because of the higher boiling point, the C4F7N cannot be mixed in a large percentage, and in order to replace the SF6 at 5bar (abs.), its mixture have to elevate the gas pressure more than 2bar. In brief, the investigations in this paper gives a basic reference for the use of co-friendly SF6 alternative gases, and more deeper studies will be carried out in series, aiming at the real typical insulating structures of the electrical equipments.