Study on Impulse Discharge Voltage Calculation of Environmentally Friendly Insulation Gas in Slightly Non-Uniform Electric Field

The environmentally friendly insulating gas C₄F₇N/CO₂ has become a popular alternative to the insulating gas SF₆ in recent years. The internal structure of electrical equipment should be taken into account in normal operation, and its electric field distribution is designed and manufactured according to a slightly non-uniform electric field. A large number of high-voltage experiments are usually needed to study the impulse discharge voltage of gases, while new environmentally friendly insulating gases are expensive and have a large amount of experience. The current calculation model of gas discharge voltage is only suitable for special gases, and the calculation conditions (electric field non-uniformity, air pressure, polarity) are specific, making it difficult to match engineering. In this paper, the calculation model of impulse discharge voltage is established with a sphere–plane electrode in a slightly non-uniform electric field, and the calculation formula for key parameters is deduced. SF₆ gas and C₄F₇N/CO₂ mixed gas were used as cases to calculate, and the calculation model was verified to be effective via comparison with the experiment.