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Open access

M. Szewczyk

Abstract

Very fast transient overvoltages (VFTO) originate from steep voltage breakdowns in SF6 gas that are inherent to operation of any switching device of the gas-insulated switchgear (GIS) type. For power stations with voltage ratings exceeding 500 kV, the ratio between equipment rated- and withstand-voltage levels becomes relatively low, which causes the VFTO peak values to reach the component’s insulation withstand-voltage levels, thus becoming a design factor for high- and ultra-high voltage GIS. While well-established approach to VFTO analyses involves only single VFTO events (the so-called single-spark approach), there is often the need to analyze the entire VFTO generation process, for which the multi-spark approach to VFTO modeling is to be employed. The multi-spark approach allows one to evaluate the VFTO impact on the GIS disconnector design along with the impact of the VFTO on selection and dimensioning of the VFTO damping solutions. As the multi-spark approach to VFTO modeling is now being increasingly used in UHV GIS developments as well as for the insulation co-ordination studies of power stations, the present paper is motivated by the need to report on the VFTO multi-spark modeling approach and to lay a common ground for development works that are supported extensively with VFTO simulations. The paper presents physical assumptions and modeling concepts that are in use in such modeling works. Development of the multi-spark GIS disconnector model for VFTO simulations is presented, followed by an overview of examples of the model application for the GIS development works and for insulation co-ordination studies.

Open access

A. Gąska, D. Szewczyk, P. Gąska, M. Gruza and J. Sładek

Abstract

Nowadays, simulators facilitate tasks performed daily by the engineers of different branches, including coordinate metrologists. Sometimes it is difficult or almost impossible to program a Coordinate Measuring Machine (CMM) using standard methods. This happens, for example, during measurements of nano elements or in cases when measurements are performed on high-precision (accurate) measuring machines which work in strictly air-conditioned spaces and the presence of the operator in such room during the programming of CMM could cause an increase in temperature, which in turn could make it necessary to wait some time until conditions stabilize. This article describes functioning of a simulator and its usage during Coordinate Measuring Machine programming in the latter situation. Article also describes a general process of programming CMMs which ensures the correct machine performance after starting the program on a real machine. As an example proving the presented considerations, measurement of exemplary workpiece, which was performed on the machine working in the strictly air-conditioned room, was described

Open access

A. Szewczyk-Nykiel, M. Skałoń and J. Kazior

Abstract

Present study describes results of research conducted on sinters manufactured from a powdered AISI 316L austenitic stainless steel modified with an addition of boron-rich master alloy. The main aim was to study impact of the master alloy addition on a corrosion resistance of sinters in 0.5M water solution of NaCl. In order to achieve it, a potentiodynamic method was used. Corrosion tests results were also supplemented with a microstructures of near-surface areas. Scanning electron microscope pictures of a corroded surfaces previously exposed to the corrosive environment were taken and compared. It was successful to increase the corrosion resistance of AISI 316L sinters modified with master alloy. It was also successful in particular samples to obtain a densified superficial layer not only on the sinters sintered in the hydrogen but also on sinters sintered in the vacuum. No linear correlation between presence of the densified superficial layer and the enhanced corrosion resistance was noticed.

Open access

Magdalena Szewczyk and Małgorzata Kacprzak

Streszczenie

Rozbudowane górnictwo surowców skalnych w Polsce obejmuje przede wszystkim tereny południowej i centralnej części kraju. Szczególnie mocno rozwinięty jest tu przemysł wydobywczy surowców węglanowych, gdzie geologiczne zasoby bilansowe wapieni i margli na koniec 2011 r. wyniosły powyżej 18 mln t. W czołówce pod względem eksploatacji skał wapiennych znajduje się m.in. region opolski, krakowsko-częstochowsko-wie- luński, świętokrzyski i lubelski. Sektor cementowo-wapienniczy w tych regionach obejmuje największe kopalnie z rocznym wydobyciem przekraczającym 1 mln t/rok. Pod względem wielkości wydobycia górnictwo wapieni i margli w Polsce zajmuje znaczną pozycję z rocznym wydobyciem na poziomie 49 mln t/rok. Największy udział w wydobyciu wapieni i margli przypada dla województw: świętokrzyskiego powyżej 22 mln t/rok i opolskiego powyżej 9 mln t/rok. Zakłady górnicze eksploatujące kopaliny dla przemysłu cementowego i wapienniczego w całości są sprywatyzowane, a ich właścicielami są renomowane europejskie i światowe firmy, których in­westycje produkcyjne i proekologiczne powodują, że branża ta staje się jedną z najnowocześniejszych w Polsce. Pomimo postępującego rozwoju branży cementowo-wapienniczej stan zagospodarowania złóż wapieni i margli kształtuje się na średnim poziomie. Obecnie eksploatowanych jest około 33,6 % rozpoznanych złóż, gdzie udział złóż rozpoznanych zarówno wstępnie jak i szczegółowo, w zasobach geologicznych bilansowych, przekracza 60%. Na stan zagospodarowania surowców cementowo-wapienniczych mają wpływ przede wszystkim ogra­niczenia sozologiczne, z tego względu, że złoża często położone są w regionach o szczególnych wartościach przyrodniczych oraz wysokie koszty nabycia terenów i opłaty ponoszone w związku z koniecznością zmiany funkcji terenu. Dlatego często koszty związaneznabyciemterenuizmianąjego przeznaczeniaczyniąeksploatację złoża nieopłacalną.

Open access

E. Hanczakowska, A. Szewczyk, M. Świątkiewicz and K. Okoń

Abstract

The effect of supplementing piglet diets with acidifiers containing the short-chain fatty acids - SCFA (propionic C3 and formic) together with medium-chain fatty acids - MCFA (caprylic C8 and capric C10) on performance, nutrient apparent digestibility, intestinal microflora and small intestine structure was investigated. The study was performed on 326 piglets allocated to 5 experimental groups. They were fed a standard diet (Group I - control) or a standard diet supplemented with 0.5% propionic and formic acids (Group II - PF). Group III (PF + C8), group IV (PF + C10) and group V (PF + C8 + C10) received the same mixture as group II with a supplement of 0.2% of caprylic and/or capric acids, respectively. Apparent digestibility of nutrients and microbiological analyses were performed. The structure of jejunum mucosa was also examined. Piglets receiving capric acid (groups IV and V) had the highest body weight gains. Piglets receiving MCFA digested protein and fiber better (P≤0.05) than piglets receiving SCFA as acidifier. There was no difference in intestinal microflora except for Clostridium perfringens, the population of which was reduced by SCFA (group II). Villi of the mucosal epithelium were the highest (P ≤ 0.05) in piglets receiving SCFA with capric acid (group IV). Under the conditions of this study a mixture of SCFA (propionic and formic) with capric acid significantly improves performance of piglets.

Open access

Michał Nowicki, Maciej Kachniarz and Roman Szewczyk

Abstract

The paper presents a special measurement system for investigation of temperature influence on the indication of commercially available sensors of the magnetic field. Utilizing the developed system, several magnetoresistive and Hall-effect sensors were investigated within the temperature range from −30°C to 70°C. The obtained results indicate that sensitivity of most of the investigated sensors is unaffected, except the basic magnetoresistive device. However, Hall-effect sensors exhibit considerable temperature drift, regardless of the manufacturer.