LOAD NOISE INCREASE OF TRANSFORMERS BY LOAD HARMONICS

Electrical power and distribution transformers in field operation regularly show significant deviation in the load noise level in comparison to the sound measurements in the test field of the manufacturer where controlled and standardised measurement conditions apply. The main reason therefore are (a) the changed acoustical ambient conditions on-site caused by sound reflection and diffraction effects of nearby obstacles; (b) changed structural and acoustical resonances, and (c) the different principal operation conditions on-site. Whereas at the factory tests a pure sinusoidal current with short-circuited secondary winding is applied for load noise determination, transformers on-site operate at changed load power factors (phase angle between voltage and load-current), loading beyond the rated power (overload, partial load) as well as harmonics in the load-current. Harmonic components in the power grid are caused primarily by nonlinear loads and by the nonlinear transfer characteristic of the power grid. Any electrical device which shows a nonlinear consumption of active power or a nonlinear change of the source impedance draws a distorted current waveform even if the supply voltage is sinusoidal. With the growing use of electrical and electronic devices, distorted waveforms in power supply grid by harmonics have been largely increased within the past years. Devices like variable speed drives, six-pulse bridge rectifiers used in power electronics, and discharge lamps draw a non-sinusodial but pulsating current. Whereas most electric devices generate solely odd harmonics, some devices with fluctuating power consumption generate odd, even and also interharmonic currents [1]. Load noise is generated by electromagnetic forces acting on transformer windings. The forces are proportional to the square of the load-current (Section 2.2). This quadratic response behaviour generates winding vibrations at frequencies beyond the power frequency. In case of harmonics in the load-current, the resulting magnetic force and noise components have harmonics as well- with a more complex frequency spectrum. The related increase of the load noise level must be considered in the estimation of the total noise level of transformers under real load conditions. The question arise how to predict the resulting noise level at these loading conditions to guarantee the maximum allowed sound level at the transformer site as requested by legislative regulations or the owners specification. Starting from basic principles, we describe and quantify the generation of harmonics in winding forces, winding vibrations and load noise of electrical transformers caused by load harmonics. A calculation scheme for a fast and practically accurate estimation of the increase in the load noise level for a given load spectrum presented. The effects of A-weighting and frequency-dependent sound radiation efficiency of transformers to the total noise level are discussed. Finally, three practical examples are given

Magnetic vector potential and magnetic field intensity due to a finite current carrying cylinder considering a variable current density along its axial dimension

With the aim of introducing a computationally efficient solution for problems such as the fast computation of magnetic field magnitudes and forces in coils and windings, this paper presents analytical expressions for the magnetic vector potential and magnetic field intensity in radial and axial directions due to a finite cylinder with infinitesimal wall thickness carrying a linearly varying current density between the values at the lower and upper ends. All expressions have been derived in terms of complete elliptic integrals of first, second and third kind, whose evaluation is achieved by means of very fast algorithms. The formulas presented make possible the fast computation of magnetic field at any point in space at reduced computational cost. The formulation is not only specially suited for modeling the current distribution in foil windings of power transformers but also for representing the magnetization of transformer core legs. The present method is also useful for efficient modeling of cylinders with constant current density since it is a generalization of this especial case. Finally, an example is presented where the results achieved using the proposed method are compared with those obtained using the finite element method showing a very good agreement between them.Fil: Díaz, Guillermo A.. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; ArgentinaFil: Mombello, Enrique Esteban. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; ArgentinaFil: Stephan, Voss. No especifíca

Health indices for the evaluation and monitoring of health in children and adolescents in prevention and health promotion: a scoping review

BACKGROUND Health indicators are used in different settings to monitor health outcomes. Child and adolescent health is arguably one of the most important areas for the application of indices and indicators in prevention and health promotion. Although single health indicators may be better suited to display the complexity of the health status and its determinants, a selected set of indicators will still offer a complex picture. Therefore, it is argued that a group of indicators combined into an index may offer a pragmatic tool that is easier to use in order to inform stakeholders. METHODS A scoping review was conducted to identify and describe health indices that monitor and evaluate health of children and adolescents and to appraise the quality and value of the identified indices that may guide the further applications of these indices in particular settings. The three bibliographic databases MEDLINE, EMBASE and PsycINFO were searched and a double screening of titles and abstracts as well as double screening of full texts was performed. Indices contained in these studies were analysed in terms of focus and composition and evaluated in terms of quality criteria. RESULTS The scoping review identified 36 eligible studies with 18 health indices in six thematic categories. Of the identified indices, seven indices focus on anthropometrical variables, three indices focus on special aspects of newborns and five indices focus on oral health. One index assesses \textquotedblhealthy lifestyle\textquotedbl and one \textquotedblfunctional ability\textquotedbl whereas one index a combination of different aspects. Most indices are calculated by using primary health data. CONCLUSIONS Alone or in combination with single sets of indicators, indices in six major thematic domains may be used as pragmatic tools for monitoring children's and adolescents´ health and the evaluation of interventions in health promotion and prevention settings

Integrated Disaster Risk Management (IDRM): Elements to Advance Its Study and Assessment

This study analyzed the international key literature on integrated disaster risk management (IDRM), considering it a dynamic sociocultural process subjected to the historical process of social formation, offering a closer look at the concept while exploring conceptual elements and ideas to advance IDRM in both national and international contexts. Methodologically, the study adopted a literature review strategy, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) approach, combined with qualitative content analysis. This article examines the history of IDRM, discusses current challenges for implementation, looks at some experiences, and proposes avenues for further research. Some findings point out the lack of an overarching IDRM approach, which is characterized by a rather disperse set of ideas and experiences concerning what IDRM is and how it should be operationalized, thereby revealing the need for a more comprehensive theory and methodologies to further advance it. Other findings highlight that IDRM encompasses different kinds and levels of “integrations” that go from internal (that is, disaster risk reduction and management domains) to external (that is, all societal processes such as sustainable development), including temporal and spatial integrations. Hence, we are talking about a multidimensional integration of disaster risk management. In this regard, the article proposes four dimensions for integration: sectoral, spatial/hierarchical, temporal, and externally with other cross-cutting societal challenges, especially climate change and sustainable development. These dimensions cover 29 ideas for indicators or “proto-indicators” to guide the discussion, exploration, and analysis of IDRM in specific contexts

Improved Durability of Wood Treated with Nano Metal Fluorides against Brown-Rot and White-Rot Fungi

Low-water soluble metal fluorides such as magnesium fluoride (MgF2) and calcium fluoride (CaF2) were evaluated for decay protection of wood. Initially, the biocidal efficacy of nano metal fluorides (NMFs) against wood destroying fungi was assessed with an in-vitro agar test. The results from the test showed that agar medium containing MgF2 and CaF2 was more efficient in preventing fungal decay than stand-alone MgF2 or CaF2. These metal fluorides, in their nanoscopic form synthesized using fluorolytic sol-gel synthesis, were introduced into the sapwood of Scots pine and beech wood and then subjected to accelerated ageing by leaching (EN 84). MAS 19F NMR and X-ray micro CT images showed that metal fluorides were present in treated wood, unleached and leached. Decay resistance of Scots pine and beech wood treated with NMFs was tested against wood destroying fungi Rhodonia placenta and Trametes versicolor in accordance with EN 113. Results revealed that mass losses were reduced to below 3% in wood treated with the combination of MgF2 and CaF2. It is concluded that NMFs provide full protection to wood even after it has been leached and can be used as wood preservatives in outdoor environments.Peer Reviewe

Occurrence and distribution of Amphidomataceae (Dinophyceae) in Danish coastal waters of the North Sea, the Limfjord and the Kattegat/Belt area

Some species of the dinophytes Azadinium and Amphidoma (Amphidomataceae) produce azaspiracids (AZA), lipophilic polyether compounds responsible for Azaspiracid Shellfish Poisoning (AZP) in humans after consumption of contaminated seafood. Toxigenic Amphidomataceae are known to occur in the North Atlantic and the North Sea area, but little is known about their importance in Danish coastal waters. In 2016, 44 Stations were sampled on a survey along the Danish coastline, covering the German Bight, Limfjord, the Kattegat area, Great Belt and Kiel Bight. Samples were analysed by live microscopy, liquid chromatography-tandem mass spectrometry (LC–MS/MS) and quantitative polymerase-chain-reaction (qPCR) on the presence of Amphidomataceae and AZA. Amphidomataceae were widely distributed in the area, but were below detection limit on most of the inner Limfjord stations. Cell abundances of the three toxigenic species, determined with species-specific qPCR assays on Azadinium spinosum, Az. poporum and Amphidoma languida, were generally low and restricted to the North Sea and the northern Kattegat, which was in agreement with the distribution of the generally low AZA abundances in plankton samples. Among the toxigenic species, Amphidoma languida was dominant with highest cell densities up to 3×103 cells L−1 on North Sea stations and at the western entrance of the Limfjord. Azaspiracids detected in plankton samples include low levels of AZA-1 at one station of the North Sea, and higher levels of AZA-38 and -39 (up to 1.5 ng L−1) in the North Sea and the Limfjord entrance. Furthermore, one new AZA (named AZA-63) was discovered in plankton of two North Sea stations. Morphological, molecular, and toxinological characterisation of 26 newly established strains from the area confirmed the presence of four amphidomatacean species (Az. obesum, Az. dalianense, Az. poporum and Am. languida). The single new strain of Az. poporum turned out as a member of Ribotype A2, which was previously only known from the Mediterranean. Consistent with some of these Mediterranean A2 strains, but different to the previously established AZA-37 producing Az. poporum Ribotype A1 strains from Denmark, the new strain did not contain any AZA. Azaspiracids were also absent in all Az. obesum and Az. dalianense strains, but AZA-38 and -39 were found in all Am. languida strains with total AZA cell quotas ranging from 0.08 up to 94 fg cell−1. In conclusion, AZA-producing microalgae and their respective toxins were low in abundance but widely present in the area, and thus might be considered in local monitoring programs to preserve seafood safety in Danish coastal waters

Alcohol Use of German Adults during Different Pandemic Phases: Repeated Cross-Sectional Analyses in the COVID-19 Snapshot Monitoring Study (COSMO)

There is little evidence on how different COVID-19 pandemic phases influence the alcohol use behaviour of adults. The objective of this study is to investigate alcohol use frequency over different COVID-19 pandemic phases and to identify vulnerable subgroups for risky use behaviour in the German adult population. Survey waves of 14/15 April 2020 (n = 1032), 23/24 June 2020 (n = 993), and 26/27 January 2021 (n = 1001) from the COVID-19 Snapshot Monitoring (COSMO) were analysed. The mean age was 46 ± 15.3 years in April, 46 ± 15.5 years in June, and 45 ± 15.5 years in January. The gender ratio was mostly equal in each survey wave. Descriptive analyses and univariate and multivariate logistic regression analyses for individuals with increased alcohol use frequency (AUF) were performed. 13.2% in April (lockdown), 11.3% in June (easement), and 8.6% in January (lockdown) of participants showed an increased AUF. Individuals with perceived burden, high frustration levels due to protective measures, and young to middle-aged adults were more likely to increase their AUF during different pandemic phases. In conclusion, unfavourable alcohol behaviour might occur as a potentially maladaptive coping strategy in pandemics. Because of potential negative long-term consequences of problematic alcohol use behaviour on health, public health strategies should consider mental health consequences and target addictive behaviour, while also guiding risk groups towards healthy coping strategies such as physical activities during pandemics/crises

Gegensätzliche Reaktivität frustrierter Lewis-Paare mit Selen- und Bor-basierten Lewis-Säuren

Die Aktivierung von π-Bindungen in Alkin-substituierten Estern wurde mit weichen und harten Lewis-Säuren untersucht. Im Fall der weichen Selen-Lewis-Säure PhSeCl führte die sequenzielle Aktivierung der Alkine zunächst zu einer Isocumarinverbindung (1 Äquiv. PhSeCl), und dann zu einer tetracyclischen konjugierten Struktur, bei der die Isocumarin-Einheit mit einem Benzoselenopyran-System verknüpft ist (3 Äquiv. PhSeCl). Umgekehrt leitet das Boran B(C6F5)3 als harte Lewis-Säure eine Reaktionskaskade ein, bei der ein komplexes π-konjugiertes System mit einer Phthalid- und einer Inden-Untereinheit erhalten wird