Application of Load Compensation in Voltage Controllers of Large Generators in the Polish Power Grid

The Automatic Voltage Regulator normally controls the generator stator terminal voltage. Load compensation is used to control the voltage which is representative of the voltage at a point either within or external to the generator. In the Polish Power Grid (PPG) compensation is ready to use in every AVR of a large generator, but it is utilized only in the case of generators operating at the same medium voltage buses. It is similar as in most European Power Grids. The compensator regulating the voltage at a point beyond the machine terminals has significant advantages in comparison to the slower secondary Voltage and Reactive Power Control System (ARNE)1. The compensation stiffens the EHV grid, which leads to improved voltage quality in the distribution grid. This effect may be particularly important in the context of the dynamic development of wind and solar energy

Fast-Valving of Large Steam Turbine Units as a Means of Power System Security Enhancement

Fast-valving assists in maintaining system stability following a severe transmission system fault by reducing the turbine mechanical power. Fast-valving consists in rapid closing and opening of steam valves in an adequate manner to reduce the generator accelerating power following the recognition of a severe fault. FV can be an effective and economical method of meeting the performance requirements of a power system in the presence of an increase in wind and solar generation in the power system, newly connected large thermal units and delaying of building new transmission lines. The principle of fast-valving and advantages of applying this technique in large steam turbine units was presented in the paper. Effectiveness of fast-valving in enhancing the stability of the Polish Power Grid was analyzed. The feasibility study of fast-valving application in the 560 MW unit in Kozienice Power Station (EW SA) was discussed

Magnesium Coordination Chemistry: A Case Study of Magnesium Carboxylate Complexes with Hexamethylenetetramine

Three magnesium coordination compounds were obtained to explore the influence of carboxylate anions on the pattern of the formed hydrogen bonds. For their synthesis, various salts of magnesium carboxylic acid (formate, acetate, and propionate) were utilized. As an N-donor ligand, hexamethylenetetramine was employed. The supramolecular structures of the obtained compounds were determined and evaluated in Hirshfeld analysis. The length of the carbon chain of the used carboxylate anions has been proven to have a considerable impact on the self-organization of the supramolecular system by altering the three-dimensional net of the created hydrogen bonds. IR spectroscopy was used to characterize the obtained compounds, revealing significant differences between distinct systems. The thermal analysis of the investigated compounds also shows noticeable differences, demonstrating better stability of the systems containing formate anions

T CD3+CD8+ Lymphocytes Are More Susceptible for Apoptosis in the First Trimester of Normal Human Pregnancy

Aims. Normal human pregnancy is a complex process of many immunoregulatory mechanisms which protect fetus from the activation of the maternal immune system. The aim of the study was to investigate the apoptosis of lymphocytes in peripheral blood of normal pregnant patients and healthy nonpregnant women. Methods. Sixty pregnant women and 17 nonpregnant women were included in the study. Lymphocytes were isolated and labeled with anti-CD3, anti-CD4, and anti-CD8 monoclonal antibodies. Apoptosis was detected by CMXRos staining and analyzed using the flow cytometric method. Results. We found significantly higher apoptosis of total lymphocytes in peripheral blood of pregnant patients when compared to healthy nonpregnant women. The percentage of apoptotic T CD3+CD8+ cells in the first trimester was significantly higher when compared to the third trimester of normal pregnancy. The ratio of T CD3+CD4+ : T CD3+CD8+ apoptotic lymphocytes was significantly lower in the first trimester when compared to other trimesters of pregnancy and to both of the phases of the menstrual cycle. Conclusions. The higher apoptosis of T CD3+CD8+ lymphocytes and the lower ratio of T CD3+CD4+ : T CD3+CD8+ apoptotic cells in the first trimester of normal pregnancy may suggest a higher susceptibility of T CD3+CD8+ cells for apoptosis as a protective mechanism at the early stage of pregnancy

Microbiologically Pure Cotton Fabrics Treated with Tetrabutylammonium OXONE as Mild Disinfection Agent

The microbiological purity of textiles plays a pivotal role in the use of textiles, especially in hospitals and other medical facilities. Microbiological purity of cotton fabric was achieved by a new disinfection method using tetrabutyloammonium OXONE (TBA-OXONE) before washing. As a result of the disinfection, the cotton fabric became microbiologically pure, despite the markedly decreased washing time with respect to the widely used standard procedure. Shortening of the washing time allowed for significant energy savings. In addition, the effect of the number of disinfection and washing cycles on the tensile properties and tearing force of the fabric was examined. After 120 disinfection and washing cycles the mechanical properties of cotton fabric were only slightly worsened