7 research outputs found
Investigating the effect of several model configurations on the transient response of gas-insulated substation during fault events using an electromagnetic field theory approach
Assessment of very fast transient overvoltage (VFTO) requires good knowledge of the behavior of gas-insulated substation when subjected to very high frequencies. The international standards and guidelines generically present only recommendations regarding the VFTO suppression without a technical and mathematical background. Therefore, to provide an accurate image regarding the critical locations across a gas-insulated substation (GIS) from a transient response point of view, a suitable modeling technique has to be identified and developed for the substation. The paper aimed to provide an accurate assessment of the GIS holistic transient response through an electromagnetic field theory (EMF) approach. This modeling technique has always been a difficult task when it came to gas-insulated substations. However, recent studies have shown that through suitable Computer-aided design models, representing the GIS metallic ensemble, accurate results can be obtained. The paper investigated several simplifications of the computational domain considering different gas-insulated substation configurations in order to identify a suitable modeling approach without any unnecessary computational effort. The analysis was performed by adopting the partial equivalent element circuit (PEEC) approach embedded into XGSLab software package. Obtained results could provide useful hints for grounding grid designers regarding the proper development and implementation of transient ground potential rise (TGPR) mitigation techniques across a gas-insulated substation
VLTI status update: a decade of operations and beyond
We present the latest update of the European Southern Observatory's Very
Large Telescope interferometer (VLTI). The operations of VLTI have greatly
improved in the past years: reduction of the execution time; better offering of
telescopes configurations; improvements on AMBER limiting magnitudes; study of
polarization effects and control for single mode fibres; fringe tracking real
time data, etc. We present some of these improvements and also quantify the
operational improvements using a performance metric. We take the opportunity of
the first decade of operations to reflect on the VLTI community which is
analyzed quantitatively and qualitatively. Finally, we present briefly the
preparatory work for the arrival of the second generation instruments GRAVITY
and MATISSE.Comment: 10 pages, 7 figures, Proceedings of the SPIE, 9146-1
Soberania imperial, espaços de exceção e o campo de Guantánamo: desterritorialização e confinamento na "guerra contra o terror"
Nuovi approcci per la valutazione della sicurezza degli impianti di terra a frequenza industriale.
Dispersori di terra per sistemi elettrici di distribuzione. Nuove soluzioni per bonifica e realizzazione
Vengono illustrate alcune possibilità offerte dall’utilizzo di elementi infissi a media e grande profondità nella bonifica e
realizzazione di impianti di terra per reti gestite con centro stella a terra. Nella prima parte del lavoro viene discussa la possibilità di
bonifica di dispersori di impianto con picchetti infissi a grande profondità . Viene quindi descritto nel dettaglio un intervento di
bonifica di una Cabina Primaria esistente. Nella seconda parte viene trattato il problema della bonifica dei dispersori di linea
confrontando le caratteristiche di dispersori di nuova geometria a quelli tradizionali unificati ENEL. Nella terza parte vengono
riportati alcuni dati relativi ad otto interventi di bonifica con la tecnica dei dispersori a grande profondità su altrettante CP
dell’ENEL Direzione Distribuzione Trivenet
Mitigation of transient ground potential rise in gas insulated substations during very fast transient overvoltage
This paper is focused on the assessment and mitigation of the transient response of a Gas Insulated Substation's (GIS) grounding grid to the fault due to voltage breakdown using the Partial Element Equivalent Circuit (PEEC) numerical approach. The adopted analysis methodology considers the magnetic induction by quantifying the electromagnetic couplings generated within the metallic components contained by the GIS configuration. The Transient Ground Potential Rise (TGPR) and transient current are computed and analyzed at several locations inside of GIS housing. With the aid of 3D graphical representation, the maximum amplitudes of the TGPR across the substation are illustrated. The mitigation efforts are considerably optimized by assuming the grounding grid sub-system is responsible for high frequency fault energy clearance based on identification method. By adopting several simplifications of the earthing system during the computational process, from a step-by-step analysis, it has been discovered that the grid located beneath the GIS enclosure will mostly attenuate the TGPR across the GIS building. Based on the aforementioned findings a successful mitigation technique is implemented