Influence of the filling gas mixture on the interruption capability of medium voltage load break switches

In today’s medium voltage switchgear SF6 is commonly used as insulating and arc quenching medium. Because of its high potential impact on the environment a substitution with an environmentally friendly alternative is pursued. In this paper the influence of the mixing ratio of carbon dioxide nitrogen mixtures as filling gas on the interruption capability in medium voltage load break switches is investigated. The interruption capability is regarded by means of the thermal interruption performance as well as the dielectric recovery of a model load break switch. The model load break switch allows an axial arc blowing with variable pressure and uses an exchangeable nozzle system

Bridge of love: knowledge and sound ecologies in the Atlantic ocean

The Lisbon neighborhood of Alto da Cova da Moura is an immigrant community consisting mainly of Africans from former Portuguese colonies. Referred to by residents as, “Kova M”, it is home to the performative practices of the Kola San Jon. This performative practice from Cape Verde assembles music, dance, voice and artifacts with a distinctly religious flavor. The religious devotion to St. John Baptist is illustrated by the prevalence of religious iconography and attendance at masses and pilgrimages. For centuries, the Atlantic Ocean represented an interstitial space that linked Africa to Europe. The Kola San Jon is an expressive practice which, in contrast to the Morna, helps to build and strengthen this link. The sea as both a living entity and a metaphorical concept that challenges traditional concepts of boundaries contributes to an inclusive sound ecology that predominates the performative practices and cultural traditions of the Kola San Jon and are suggestive of a “space” where identities are constructed and dialogue takes place through emotions such as love. Drawing on extensive ethnography both in Cape Verde and among the communities in “Kova M”, I discuss the applicability of new epistemological concepts that have grown out of my dialogical encounter in the “field”

Ausschaltvermögen von Mittelspannungs-Lasttrennschaltern bei Verwendung atmosphärischer Lösch- und Isoliergase

Medium voltage load break switches are essential components in today’s energy systems. As a part of secondary medium voltage switchgear they are responsible for interrupting load currents and ensuring a safe insulation distance in the off-state. In the course of the ongoing medium voltage grid expansion, mainly gas insulated switchgear filled with sulfur hexafluoride (SF6) is installed. The use of SF6 permits a compact and reliable switchgear design. In contrast, SF6, with a global warming potential of 23.500 CO2 mass equivalents, is the most potent greenhouse gas known. A substitution of SF6 while keeping the size and reliability of the switchgear is desirable. In the process of subtituting SF6 in medium voltage switchgear the load break switch is the critical component, as the gas serves as insulating and quenching medium. Possible substitutes have a lower dielectric strength as well as a lower arc quenching capability. Hence, a fundamental redesign of the load break switch is necessary. The objective of this thesis is the identification and quantification of the main influencing parameters on the switching capability of a medium voltage load break switch filled with an alternative insulating gas. In a parametric study the thermal interruption capability and the dielectric recovery are determined for different design parameters of a model load break switch. A sufficient arc cooling is essential for a sufficient interruption performance and can be ensured by a convective cooling by axial arc blowing as well as by the “Hartgas“-effect, resulting from polymer ablation close to the arc. Both mechanisms can be influenced by the design of the load break switch. From the experimental results of the study a catalog of design criteria is derived. These criteria are used to develop a demonstrator of an environmentally friendly medium voltage load break switch. At the end of the thesis, the demonstrator’s interruption capability is successfully tested according to standards

Switching Behaviour of a Series Connection of a Vacuum Interrupter and a Gas Circuit Breaker

After being in the focus of sciences' and industry's research and development activities for many years, the investigation of possible SF6 gas-alternatives has been even more intensified after the revision of the European F-Gas regulation 517/2014. As natural gases yield a significantly lower dielectric strength in comparison to SF6, new challenges arise for the design of high voltage switchgear. Vacuum interrupters are environmentally friendly, reliable and able to withstand steep rising transient recovery voltages. In the last years, first installations of switchgear based on vacuum switching technology in sub-transmission level are in operation. One option for the realization of a SF6 free high voltage switchgear for transmission level is the combination of a gas circuit breaker filled with an atmospheric gas with a vacuum interrupter in a hybrid switchgear. In this contribution the voltage distribution and switching behavior of a hybrid circuit breaker is experimentally investigated

Development of an Experimental Approach for Determining the Arc Quenching Capability of Different Gases

After being in the focus of sciences' and industry's research and development activities for many years, the investigation of possible SF6 (sulfur hexafluoride) gas-alternatives has been even more intensified after the revision of the European regulation on fluorinated gases in 2014. This contribution focuses on the scientific assessment of the technical performance of several SF6 gas-alternatives - gases and gas mixtures - currently under discussion. Therefore, a reference experimental setup, that allows the determination of the arc quenching capability of different gases as well as the axial resistance distribution of the switching arc around current zero crossing, is developed. Additionally, first experimental results for the thermal interruption capability and the arc resistance distribution of SF6 and possible SF6 gas-alternatives are shown