Dielectric performance of HFO-gas mixtures

There is a strong demand in the power and pulsed power industries to find potential environmentally friendly alternative gases and liquids with advanced dielectric properties with the aim of replacing of SF6 gas in high-voltage equipment due to environmental concerns. Several alternative gases such as CF3I and hydrofluoroolefin and the mixture of these gasses with buffer gases have been considered as potential substitutes for SF6. However, the breakdown properties of these gases and gas mixtures are not well understood and their characteristics require further investigation in order to establish and expand potential practical applications. In this paper, the breakdown behaviour of gasses with well-established characteristics (air, CO2, N) and those of hydrofluoroolefin HFO1234ze/CO2 gas mixtures have been obtained in a dedicated point-plane topology, under the positive and negative voltage stress. The gas pressure in the test cell was in the range from 1 bar to 10 bar (abs) and all tests were conducted at room temperature. The obtained breakdown and corona ignition voltages will help in further development and optimisation of the plasma closing switches operating in the corona stabilisation regime and filled with environmentally friendly gases.