Modern Gas Insulated Switchgear (GIS) technology has been undergoing continual development since its introduction in the 1960's when the use of SF 6 as arc extinguishing and isolating medium was first introduced, and whilst many may consider this technology as mature, there have been continuous development driven changes in GIS design, manufacture, test and operation.
Consistent research and innovative development led to the nowadays compact and overall optimized switchgear. Today, GIS technology consists typically of a modular design and is filled with a minimum of SF6. The standardized structure is made to match various individual customers' specifications and allows realizing almost all substation configurations accordingly.Furthermore, it offers low life cycle costs with reduced maintenance and can be used for indoor and outdoor applications. And above all, green substation aspects are strongly considered.
Keywords-gas insulated switchgear (GIS), insulating gas sulfur hexafluoride SF6, GIS development and trends
Over the recent five years, the high-strength rails of the new generation of type R65 of steel grade K76F of the production of the plant «MK Azovstal» as well as high-strength rails of type R65 of steel grade 76F of Russian production with their welding in continuous welded track are more and more often laid at the railroads of Ukraine. At the E.O. Paton Electric Welding Institute the comprehensive investigations of weldability of these rails were carried out using flash-butt method with the aim of development of industrial technologies. In welding of all the investigated batches of high-strength rails the required values of mechanical properties of welded joints were obtained at welding modes, characterizing by energy input 1.5-2 times lower than that in welding of rails of previous generations. The welding technology using pulsed flashing was developed providing a highly-concentrated heating and formation of quality joints of high-strength rails of different production, as well as the new generation of machines for flash-butt welding of high-strength rails under the stationary and field conditions was developed. 10 Ref. The laying of high-strength rails of the new generation with their welding in continuous track is more and more widely used at the railroads of Ukraine. Mostly high-strength rails R65 of steel grade K76F of production of «MK Azovstal», as well as high-strength rails R65 of steel grade 76F of Russian production are applied. At the PWI the comprehensive investigations of weldability of these rails were carried out using flash-butt method with the aim of development of industrial technologies for their welding. At the same time, the weldability of modern high-strength rails R350HT produced by well-known companies «Voes-talpine Schienen GmbH» (Austria), and rails VS350Ya 350LDT of «Nippon Steel» (Japan) was also investigated. Table 1 shows chemical composition and mechanical properties of the mentioned steels.In the manufacture of all the investigated rails the advanced technologies of converter production with the continuous casting of steel and continuous rolling are used.For the rails of steel K76F the differentiated hardening and for steel 76F the volumetric one are used. The hardness of layer of steel K76F hardened over the surface of rail head is HV 374-401 (Figure 1
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