Szczecin, Poland
Szczecin, Poland

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Zimin Z.S.,Saint Petersburg State University | Orlovich R.B.,ZUT | Gorshkov A.S.,Saint Petersburg State University
Magazine of Civil Engineering | Year: 2013

Because of the increasing regulatory requirements for heat-shielding properties of the exterior walls multi-layer building envelope became widespread. National practice of operation of multilayer outside walls revealed their increased defects, and first of all, this refers to the facing layer, usually performed with the stones with high voidage. Facing layer besides its aesthetic properties should reliably protect the internal structures from the negative environmental impact in the course of the operation period of a building. This can only be achieved through an analysis of its work (both the strength and heat engineering), which was often out of sight. The purpose of the study was to assess the possibility of further widespread use of stone masonry with a high voidage as the facing outer layer in Russia, and to identify the most efficient way to analyze the stress-strain state of the top layer. The foreign experience in using the hollow stones was considered, relevant strength and thermal engineering calculations were made. The conclusions on the renunciation of widespread application of stones of high voidage for lining multilayer walls and the possibility of using stones with not more than 15% range of hollowness were made. It was also concluded that the most reliable mode of deformation of the facing layer can be obtained from the joint strength and thermal calculations based on the results of monitoring of existing buildings, as well as field and laboratory tests.

Orlovic R.B.,ZUT | Rubtsov N.M.,Saint Petersburg State University | Zimin S.S.,Saint Petersburg State University
Magazine of Civil Engineering | Year: 2013

Due to increasing regulatory requirements for exterior wall thermal insulation properties multi-layer building envelope is widely used. National practice of using multi-layer exterior walls revealed their increased deficiency. The strength properties of the anchor ties are not regulated and often unknown. Purpose of the study was to assess the state of the question, to analyze existing design solutions used in the construction in Russian Federation and also to conduct a series of laboratory tests to determine their bearing capacity of the main anchor ties currently used. The most common mistakes in applying anchors are analyzed. The results of foreign researchers are given. Two series of experimental studies of bearing capacity and deformability of anchors are presented. The dependencies of the pulling force on the type of anchors and strength properties of masonry mortar joints are obtained.

Wankowicz J.,Energetyki Instytut | Bielecki J.,Energetyki Instytut | Szrot M.,Energo Complex | Subocz J.,ZUT | Malewski R.,Malewski Electrical
43rd International Conference on Large High Voltage Electric Systems 2010, CIGRE 2010 | Year: 2010

Recently, HV bushing failures were reported, which destroyed large network transformer. These transformers were produced some thirty years ago by the local manufacturer who then designed the internal insulation with a large safety margin, but 400 kV and 220 kV bushings were imported. These oil-type bushings were designed for approximately 30-year technical life. Most of them are still in a relatively good condition but some have developed on-coming insulation fault. Simultaneous replacement of all, nearly 400 bushings is impossible, considering their long delivery time and high cost. An effort was initiated to develop diagnostic procedures and a monitoring system to identify the bushings to be replaced first. Such diagnostics shall be based on a known mechanism of insulation degradation. One of them is due to penetration of atmospheric moisture into the bushing through aged sealing gaskets and gradual increase of water content in the bushing core. In such case the highest concentration of moisture is expected at the outer surface of the core. Another cause is the manufacturing technology of oil-type bushings, which are heated in vacuum chamber to extract moisture trapped in thin paper layers separated by co-axial aluminum foils. The moisture is first evaporated from the paper layer edges, but if the vacuum is applied too fast then the evaporation becomes very intense. The latent heat of evaporation (enthalpy) is absorbed, and the temperature distribution along the bushing axis drops near the core edges. This local temperature drop prevents an efficient extraction of moisture trapped in the middle section of the paper layers. In principle, the manufacturing technology requires a slow lowering of the pressure in the oven, but it may take a few weeks to dry 400 kV bushing. An attempt to shorten this time results in leaving a wet paper pocket usually near the bushing mid-length. Acceptance tests that involve measurements of capacitance and tan δ do not reveal such small pocket of wet paper, since they show an average of the whole cellulose volume. Different diagnostic procedures used to assess bushing insulation condition were evaluated in view of an effective measurement of moisture content in cellulose. Records of polarization and depolarization current can be processed to reveal excessive moisture content. A comparison of frequency-resolved measurement of bushing capacitance and tan δ, as well as tan δ versus test-voltage characteristic, allow to identify bushings with wet-cellulose insulation. AC leakage current recording has been implemented in many bushing monitoring-systems for long time. However, such monitoring provides a reliable warning when the internal fault has reached an advanced stage. Conventional measurement methods of partial discharges in the bushing mounted on transformer in substation are hampered by a high-level of electromagnetic perturbations. However, the developing fault can be revealed by detection of the high-frequency electromagnetic field radiated from the bushing.

Biel W.,Katedra Hodowli Trzody Chlewnej | Maciorowski R.,ZUT
Zywnosc. Nauka. Technologia. Jakosc/Food. Science Technology. Quality | Year: 2012

The research material consisted of grains of six wheat cultivars (Triticum aestivum L.) harvested in 2007 and 2008 (spring cultivars: Torka, Korynta, Cytra, Zadra; winter cultivars: Fregata and Markiza). The analyses comprised the contents of: dry mass, total protein, crude fat, fibre, total carbohydrates, fibre fraction, mineral compounds, amino acids, and nutritional parameters of protein (CS, EAAI, and PER). The Korynta cultivar was characterized by the highest content of protein (176 g/kg d.m.), whereas the Markiza cultivar. - by the lowest content of protein (151 g/kg d.m.). The content of crude fibre in the grains of spring cultivars was lower than in the grains of winter cultivar. The grains of Fregata and Markiza winter cultivars were characterized by the highest content of lignin (ADL). A high content of exogenous amino acids was found in the grains of Markiza cultivar and this was reflected in a high nutritive value computed on the basis of CS and EAAI parameters and of the predicted PER value. In all the samples investigated, lysine appeared to be the first amino acid to limit the value of protein value (CSMH, CSWE).

Holowaty J.M.,ZUT | Wichtowski B.,ZUT
Structural Engineering International: Journal of the International Association for Bridge and Structural Engineering (IABSE) | Year: 2013

The long-term use of steel bridges leads to changes in the mechanical properties of their structural steels. This issue is demonstrated in a study of cast steels from four railway truss bridges built in 1875. The tests for each bridge involved an analysis of the chemical composition, determination of hardness and toughness, along with yield strength and ultimate strength. The tests made it possible to calculate the current mechanical properties of steels and to estimate their fracture toughness. One of the bridges in the study was built from low-carbon steel and the others from high-carbon steel, which was not thought to be used at that time. An assessment of the current mechanical properties of the steels allowed the bearing capacities of the bridges to be estimated and, following this, technical designs for their upgrading and repair to be drawn up.

Experiences in moisture contents assessment in paper-oil insulation of transformers with advanced ageing processes have been presented. It was found that joint measurement RVM+PDC increases quality of assessment, especially for transformers with non-homogenous morphology of insulation. For water contents in cellulose higher that 3% it is necessary to take into consideration for analysis results of oil tests. The measurement RVM+PDC after considering oil tests allows to identify deposits on the active part of transformers.

Szrot M.,Energo Complex Sp. z o.o. | Subocz J.,ZUT
Przeglad Elektrotechniczny | Year: 2010

Relaxation processes in oil impregnated pressboard with various moisture contents have been analysed on the basis of universal Jonscher dielectric response law and multi-parameter Debye and Curie-Schweindler model. It was found that for moisture contents on the level of 3% there is the change of polarisation and relaxation mechanisms and nonlinear effects starts to grow, which is related to ion mass transport in macroscopic range. As an effect in highly moisturized pressboard it is expected to obtain large errors in moisture contents assessment with RVM and FDS methods.

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