Simulation and validation of pressure rise in a HV circuit breaker with SF6 and alternative interrupting media

Superior characteristics of SF6 gas have enabled its successful use as the interruption media in high voltage circuit breakers. Unique combination of physical properties considers high dielectric strength, high thermal interruption capability and high heat transfer performance. However, having in mind its high global warming potential (GWP), long term use of SF6 gas in the future should be called into question. Considering that CO2 has much lower GWP than the SF6, it represents a promising alternative, but still with known inferior breaking performance. Therefore, careful investigation of the CO2 gas behavior should be obtained. In the present work, pressure rise in a high voltage circuit breaker during no-load operation has been simulated and measured for SF6 and CO2 gas, followed with the results comparison. For simulation of high voltage circuit breakers operation, computer program HV CB Simulation, which takes into consideration interaction between the interrupting unit and the driving mechanism is used. Thermodynamic properties of gases are calculated using highly accurate equations of state explicit in Helmholtz free energy.