A Ranking Algorithm for the Thermal Interruption Ability of Potential SF₆ Alternative Gases

A ranking algorithm is proposed to aid the screening or initial assessment of different gases for their thermal interruption capability in high voltage gas-blast circuit breakers. The algorithm is directly based on the gas material properties without involving any complicated arc simulation. Despite that it does not explicitly consider the influence of product design, the ranking results based on the proposed algorithm show good alignment with laboratory obtained thermal interruption data of five gases and commercial-scale test data for three promising SF₆ alternative gases. An in-depth analysis of the influencing factors and mechanisms responsible for the differing thermal interruption abilities of gases has been carried out, showing that the dominance of the arc column size near current zero in the arc cooling process is a natural consequence of the gas properties, especially the product of density and specific heat at constant pressure and electrical conductivity over the temperature range of 500K to 15,000K.