Investigation on the spatial arc resistance distribution of switching arcs in gas filled high voltage circuit breakers

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In the field of high voltage circuit breakers self-blast circuit breakers filled with sulphur hexa fluoride (SF6) are state of the art. They are used for switching electric circuits of the high voltage power supply systems. As these breakers serve as protective components, they are required tointerrupt nominal currents as well as short circuit currents in case of a failure.Due to the high global warming potential of SF6, alternative gases are investigated aiming for economic and ecologic advantages. One possible substitute is carbon dioxide (CO2). It is necessary to investigate, if this substitute can be used and whether the design of a SF6 circuit breaker has to be changed for an optimal switching performance of a CO2 circuit breaker. A deep understanding of both the physical processes and the mathematical models, which can be applied on different gases,are required in order to save time and costduring intensive experimental tests of such a development process. This helps to improve the design of circuit breakers, which were initially optimized for SF6,for alternative gases.State of the art simulation tools for circuit breaker development and design are designed for investigating SF6 breakers with conventional geometric assemblies. As they are configured via an ex-post view on experiments they cannot be applied to alternative assemblies and gases. Hence the measurement system, which has been developed in the first project, shall be used for investigating the arcing behaviour for different gases and flow conditions. This information can be used to derive suitable simulation models. These models shall in particular be able to enhance the development of circuit breakers with SF6 substitutes. Up to now state of the art simulation tools are not able to calculate the different cooling mechanisms of CO2 in contrast to the mechanisms of SF6. In addition to the applicability of the models for different gas alternatives, the customization of breaker geometry for the quenching gas is of vital importance.Using the previous investigations as well as the developed measurement system as a basis for further parameter variations, the physical processes during the switching process of a circuit breaker can be better understood. Hence this understanding can be implemented in numerical models. Next to the variation of the nozzle-geometry and the quenching gas pressure the main focus is on the variation of the blowing gas. For instance the gases SF6, CO2 and air shall be used for the investigations. The derived simulation models are required to be applicable for the development of non-SF6 circuit breakers.