A switching arc in a model circuit breaker is studied by means of CFD simulations and optical emission spectroscopy. The arc is initiated between tungsten–copper electrodes in a carbon dioxide atmosphere and is led through PTFE (polytetrafluorethylene) nozzles. Radiation emitted by the arc plasma is absorbed by the surface of the nozzles leading to ablation of the wall material. The CFD simulations are based on a model of the arcing zone including a consistent treatment of the radiation transport and wall ablation. Carbon ion line radiation is analysed in the experiment using an optical path in the heating channel between the nozzles. Temperature profiles obtained from spectroscopy and simulations are compared. The pressure value in the arc is estimated based on the line width-intensity dependence. The obtained values correspond to the measured pressure outside the arc. Coincidence in temperature for the peak current and discrepancy on the falling edge are found and discussed.
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 PSCAD tm / EMTDC tm. 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.
Several processes have been initiated for the development of technical concepts, guidelines and common requirements of HVDC Grid Systems. For implementing extended HVDC Grid Systems on a multi-vendor basis consolidated and agreed functional requirements for equipment and solutions are needed. Providing such requirements is the role of international standardisation bodies. With the primary focus on elaborating technical standards for HVDC Grid Systems, the CENELEC Technical Committee TC8X has started a new Working Group (WG06) "System Aspects of HVDC Grids". Considering that Grid Systems are an entirely new application of HVDC technology, the first goal of this working group is elaborating a document describing clear functional specifications of different aspects for HVDC Grid Systems and associated equipment. With view on the early stage of technology this paper discusses the need for standardisation and presents the scope and methodology of WG06. The approach chosen to develop functional specifications is explained using two examples. The main contribution of this paper is to present a methodology for and the challenges in developing standards in a new field of technology and to foster discussion.
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