High voltage SF6 circuit breaker simulations based on an integral-physical enthalpy flow arc model are very powerful tool in designing and optimization of high voltage SF6 circuit breakers. This is especially important in case when full correlation between the electric arc, interrupter unit and operating mechanism parameters is needed. This paper presents computer simulations of an improved operating mechanism proven on a 123/145kV 31.5/40 kA GIS circuit breaker and verified using experimentally obtained data. The optimum value of the opening energy for rated short-circuit current interruption of the analyzed circuit breaker is estimated by using an improved operating mechanism model. In addition, several analyses have been made in order to investigate how some interrupter parameters affect the contact travel and breaking performance.

The density and SF6 gas pressure distribution along the nozzle of a HV circuit breaker plays an important role in the process of current interruption. Therefore, the analysis of the pressure distribution is essential for researchers and designers of HV SF6 circuit breakers. In this paper, simulation software for HV SF6 circuit breakers, which is based on an integral-physical enthalpy flow arc model, and CFD simulation software were used for determination of the pressures inside the interrupter chambers and pressure distribution along the nozzle. The calculated results are verified by comparison with the experimentally measured transient gas pressures for several positions inside the puffer cylinder, nozzle throat, upstream and downstream of the nozzle in a 252 kV puffer type SF6 circuit breaker during no-load operations and breaking of short-circuit currents. Comparison of the calculation results with the measurements revealed very good matching. In addition, the same simulation method is applied to some other types of HV circuit breakers and the obtained results are analyzed and discussed.