Study on Thermal Interruption and Dielectric Recovery Performance of CO2/O2/C4-FN Mixture in HVCB

The eco-efficient SF6-free high voltage switchgear is one of the most significant revolution towards the future green power grids. In recent decade, the dielectric mixture of CO2/O2/C4FN has demonstrated huge potential as an alternative to SF6. The research on the characteristics of dielectric withstands and arc extinguishing of CO2/O2/C4-FN mixture and the development of corresponding SF6-free switchgear technology have attracted increasing attentions and gained rapid progress [1][2]. In this paper, we present our study on the thermal interruption and dielectric recovery performance of CO2/O2/C4-FN mixture based on a model high voltage circuit breaker. The thermal interruption capability was quantified in terms of the highest falling slope (di/dt) of the injected current that could be interrupted by the tested gas mixtures. The comparative results show that the additive gas component C4-FN did not play a significant role on the thermal interruption capability. With the same 5% C4-FN in the mixture of CO2/O2/C4FN, the thermal interruption performance of the mixtures with 10% O2 and 5% O2 had only a slight difference. In terms of dielectric recovery performance, the complete recovery processes up to few hundreds of microseconds in the post arc phase of 18kA and 6kA high currents were measured by scanning a high voltage pulse with respect to CZ instant. The comparative results show that the addition of C4-FN significantly improved dielectric recovery performance of