The worldwide demand for flexible transmission grids leads to an increasing interest in high voltage direct current (HVDC)-voltage source converter systems resulting to the planning of radial and interconnected HVDC multiterminal grids. Since HVDC multiterminal systems have high requirements on control and protection, modular multilevel converter with full bridge (FB) submodules can be applied, preventing the handling of high fault current amplitudes. However, the feasibility of multiterminal HVDC systems utilising FB submodules has to be evaluated against the general background of selective fault handling and velocity of the fault clearing process. These necessary investigations are presented within this contribution, carried out by use of an appropriate simulation model in PSCADtm/ EMTDCtm. Thereby, requirements for protection concepts and protective devices for multiterminal systems can be further formulated. Three different variations of a protection concept have been investigated, which differ in the degree of communication structure between the converter stations and protective devices. These scenarios contain approaches with no communication, minimum communication and full communication.

Summary form only given. The high-pressure arc in a model circuit breaker is investigated by optical methods and computational fluid dynamic (CFD) simulations. The aim is to determine the plasma temperature profile and the pressure in the arc to reveal the mechanisms of ablation and pressured build-up. In addition, the comparison of experimental and theoretical results helps to confirm measurement methods as well as the simulation and underlying models.

Circuit breakers are important elements of the electric power supply system. Due to the contact separation during the switch-off process an electric arc is ignited within the circuit breaker. A forced flow of the insulating quenching gas medium is used to cool the arc influencing its conductivity. Only if the power dissipation due to cooling exceeds the electrical power input by ohmic heating, the arc is extinguished and the current is successfully interrupted in its natural zero crossing (CZ). As the impact of the cooling by the quenching gas on the resistance of the arc is considered crucial for the success of the switch-off process, the spatial distribution of the resistance is of high importance for the assessment of a circuit breakers performance. Research and development projects related to circuit breakers more and more often use computational fluid dynamics (CFD) simulations. The implemented simulation models have to be be verified by adequate experiments. This paper deals with the influence of the simulation model on the simulated spatial arc resistance distribution near current zero. Different approaches for modelling the chaotic and turbulent phenomena of the arc are introduced and their results are compared with values measured in experiments. Here the turbulence model is of main interest. On the one hand the investigations show a good agreement between simulative and experimental results for the total arcing voltage when using adequate models. On the other hand these turbulence models lead to differences in the calculated spatial arc resistance distributions – which cannot be verified by experiments so far.