Line Arrester Application on a 110 kV High Alpine Overhead Line to reduce Lightning-Caused Outages

This contribution discusses a project, which aims to increase the reliability in an existing 110 kV overhead transmission network by taking measures addressing lightning and grounding issues. Due to the fault statistic in the past, a single overhead line was identified as a main reason for the lightning-caused outages in the area. In this work a number of possibilities for the reduction of lightning-caused outages are discussed and the measures taken in the network are described. All considerations took the special geographical situation of 2300 meter above sea level, the grounding resistance of up to 1200 Ohm and the local lightning activity of more than 6 lightning strikes per km² and year into account (4 to 5 times higher than in other Austrian regions). An analytical process was carried out to evaluate relevant parameters and to develop a concept of practical measures. Within these evaluations, the footing resistance, the effectiveness of the shielding angle of the shielding wires and the line arrester locations were analyzed. A multiplicity of numerical calculations were performed to assess the application of surge arresters regarding the insulation coordination for the system. To improve the line performance and to decrease the line outage rate, a number of practical measures were applied to the 110 kV line. In the past, the double three phase systems of the 110 kV overhead line was constructional converted into one active single three phase system with two additional earth wires. According to the numerical results, 18 surge arresters have been installed in a line section of 9 towers, located in a high alpine part and in an area of high lightning activity. Three years of field experiences have shown that the theoretical investigations and the practical measures led to a significant decrease of lightning caused outages. In the year 2007 a new project was started to evaluate a reconstruction of the line into the original double three phase system. New numerical calculation routines were made to apply line arresters at this important 110 kV system in an Austrian extreme mountain region. Based on this results, a new application of line arresters and the constructional change of the system is planned

A parametric study on the axial behaviour of elastomeric isolators in multi-span bridges subjected to horizontal seismic excitations

This paper investigates the potential tensile loads and buckling effects on rubber-steel laminated bearings on bridges. These isolation bearings are typically used to support the deck on the piers and the abutments and reduce the effects of seismic loads and thermal effects on bridges. When positive means of fixing of the bearings to the deck and substructures are provided using bolts, the isolators are exposed to the possibility of tensile loads that may not meet the code limits. The uplift potential is increased when the bearings are placed eccentrically with respect to the pier axis such as in multi-span simply supported bridge decks. This particular isolator configuration may also result in excessive compressive loads, leading to bearing buckling or in the attainment of other unfavourable limit states for the bearings. In this paper, an extended computer-aided study is conducted on typical isolated bridge systems with multi-span simply-supported deck spans, showing that elastomeric bearings might undergo tensile stresses or exhibit buckling effects under certain design situations. It is shown that these unfavourable conditions can be avoided with the rational design of the bearing properties and in particular of the shape factor, which is the geometrical parameter controlling the axial bearing stiffness and capacity for a given shear stiffness. Alternatively, the unfavourable conditions could be reduced by reducing the flexural stiffness of the continuity slab

Working time regimes: A panel discussion on continuing problems

This article records a panel discussion at the Organizational Working Time Regimes conference on 31 March 2017 at the University of Graz, Austria. The discussion was moderated by Sara Louise Muhr and the panelists were Jana Costas, Susanne Ekman, Laura Empson and Dan Kärreman. The discussion both departed from yet centred on the concept of time itself: how we understand time as academics, employees and managers, and how the notion of time guides and controls all of us in various ways. Through the different perspectives that the panelists have on time and work regimes, it became evident that time – and discussions of time – is complex and context-dependent and needs to be researched as such. The discussion passionately weaved in and out of key questions on work intensification, inequality regimes and resistance to working time regimes that are deeply entwined with dynamic dialectics such as personal/professional, past/future, individual/organizational, worker/leader, good/bad. The panel in this way takes the reader through difficult discussions about what is ‘extreme’, for whom is it extreme and what interventions (if any) can be made by academics. Doing so, the panelists sensitively drew attention to our own line of work, academia, and the work regimes controlling academics

ELECTRICAL CONDUCTIVITY OF PRESSBOARD AND THE INFLUENCE OF MOISTURE CONTENT

The electrical conductivity σ is an important parameter for material condition evaluation at AC applications and is responsible for electrical field distribution in DC equipment. With a focus on HVDC equipment design, the influence of moisture content in oil-impregnated pressboard is determined in this preliminary investigation. The electrical conductivity of pressboard samples, which have been wetted artificially in the laboratory, is investigated within this work. Moisture contents between <0,3% and 5,5% could be achieved artificially through increasing pressboard moisture content levels in a climate chamber. The electrical conductivity was determined by voltage-current measurements at 20°C in the style of IEC 60093 with measurement times up to and longer than 24 hours. For these investigations, the pressboard samples with a thickness of 1 mm have been placed in an (mineral) oil-filled test vessel and stressed by a DC field with E = 3 kV/mm. It could be demonstrated that the moisture content of pressboard has a strong influence onto the electrical conductivity: An increase of electrical conductivity by a factor of around 10 for each percentage point of moisture increase up to moisture levels of around 3,5% was observed. At higher moisture contents (>5%), other mechanisms seem to govern the electrical current and the conductivity respectively, which is also discussed within the work

Bayesian calibration of a soil organic carbon model using Δ¹⁴C measurements of soil organic carbon and heterotrophic respiration as joint constraints

Soils of temperate forests store significant amounts of organic matter and are considered to be net sinks of atmospheric CO₂. Soil organic carbon (SOC) turnover has been studied using the Δ¹⁴C values of bulk SOC or different SOC fractions as observational constraints in SOC models. Further, the Δ¹⁴C values of CO₂ that evolved during the incubation of soil and roots have been widely used together with Δ¹⁴C of total soil respiration to partition soil respiration into heterotrophic respiration (HR) and rhizosphere respiration. However, these data have not been used as joint observational constraints to determine SOC turnover times. Thus, we focus on (1) how different combinations of observational constraints help to narrow estimates of turnover times and other parameters of a simple two-pool model, the Introductory Carbon Balance Model (ICBM); (2) whether relaxing the steady-state assumption in a multiple constraints approach allows the source/sink strength of the soil to be determined while estimating turnover times at the same time. To this end ICBM was adapted to model SOC and SO¹⁴C in parallel with litterfall and the Δ¹⁴C of litterfall as driving variables. The Δ¹⁴C of the atmosphere with its prominent bomb peak was used as a proxy for the Δ¹⁴C of litterfall. Data from three spruce-dominated temperate forests in Germany and the USA (Coulissenhieb II, Solling D0 and Howland Tower site) were used to estimate the parameters of ICBM via Bayesian calibration. Key findings are as follows: (1) the joint use of all four observational constraints (SOC stock and its Δ¹⁴C, HR flux and its Δ¹⁴C) helped to considerably narrow turnover times of the young pool (primarily by Δ¹⁴C of HR) and the old pool (primarily by Δ¹⁴C of SOC). Furthermore, the joint use of all observational constraints made it possible to constrain the humification factor in ICBM, which describes the fraction of the annual outflux from the young pool that enters the old pool. The Bayesian parameter estimation yielded the following turnover times (mean ± standard deviation) for SOC in the young pool: Coulissenhieb II 1.1 ± 0.5 years, Solling D0 5.7 ± 0.8 years and Howland Tower 0.8 ± 0.4 years. Turnover times for the old pool were 377 ± 61 years (Coulissenhieb II), 313 ± 66 years (Solling D0) and 184 ± 42 years (Howland Tower), respectively. (2) At all three sites the multiple constraints approach was not able to determine if the soil has been losing or storing carbon. Nevertheless, the relaxed steady-state assumption hardly introduced any additional uncertainty for the other parameter estimates. Overall the results suggest that using Δ¹⁴C data from more than one carbon pool or flux helps to better constrain SOC models

Doing Biopolitics Differently? Radical Potential in the Post-2015 MDG and SDG Debates

Post print On institutional repository or subject-based repository after a 18 months embargo, withdraw

Venezuela e ALBA: regionalismo contra-hegemônico e ensino superior para todos

Partindo de um quadro teórico neo-gramsciano crítico à globalização, este artigo aplica a nova teoria do regionalismo (NTR) e a teoria do regionalismo regulatório (TRR) à sua análise e teorização dos tratados de comércio da Aliança Bolivariana para os Povos da Nossa América (ALBA-TCP) como regionalismo contra-hegemônico na América Latina e Caribe (ALC). A ALBA está centrada na ideia de um Socialismo do Século XXI, que, como (inicialmente) também a Revolução Bolivariana da Venezuela, substitui a 'vantagem competitiva' pela 'vantagem cooperativa'. Em seu caráter de conjunto de processos multidimensionais e transnacionais a ALBA-TCP opera dentro de/transversalmente a um número de setores e escalas, ao mesmo passo que as transformações estruturais são movidas pela interação de agentes do Estado e agentes não estatais. A política de Educação Superior para Todos (ESPT) do governo venezuelano rejeita a agenda neoliberal globalizada de mercadorização, privatização e elitismo e reinvindica educação pública gratuita em todos os níveis como um direito humano fundamental. A ESPT está sendo regionalizado em um espaço educacional emergente da ALBA e assume um papel-chave nos processos de democracia direta e participatória, dos quais a construção popular (bottom-up) da contra-hegemonia e a redefinição política e econômica da ALC dependem. Antes de produzir sujeitos empreendedores conformes ao capitalismo global, a ESPT procura formar subjetividades ao longo de valores morais de solidariedade e cooperação. Isso será ilustrado com referência a um estudo etnográfico de caso da Universidade Bolivariana da Venezuela (UBV).This paper employs new regionalism theory and regulatory regionalism theory in its analysis and theorisation of the Bolivarian Alliance for the Peoples of Our America (ALBA) as a counter-hegemonic Latin American and Caribbean (LAC) regionalism. As (initially) the regionalisation of Venezuela's Bolivarian Revolution, ALBA is centred around the idea of a 21st Century Socialism that replaces the 'competitive advantage' with the 'cooperative advantage'. ALBA, as a set of multi-dimensional inter- and transnational processes, operates within and across a range of sectors and scales whilst the structural transformations are driven by the interplay of state and non-state actors. The Venezuelan government's Higher Education For All (HEFA) policy, which is being regionalised within an emergent ALBA education space, assumes a key role in the direct democratic and participatory democratic processes upon which a bottom-up construction of counter-hegemony depends. HEFA challenges the globalised neoliberal higher education agenda of commoditisation, privatisation and elitism. Rather than producing enterprising subjects fashioned for global capitalism, HEFA seeks to form subjectivities along the moral values of solidarity and cooperation

Coronal Shock Waves, EUV waves, and their Relation to CMEs. II. Modeling MHD Shock Wave Propagation Along the Solar Surface, Using Nonlinear Geometrical Acoustics

We model the propagation of a coronal shock wave, using nonlinear geometrical acoustics. The method is based on the Wentzel-Kramers-Brillouin (WKB) approach and takes into account the main properties of nonlinear waves: i) dependence of the wave front velocity on the wave amplitude, ii) nonlinear dissipation of the wave energy, and iii) progressive increase in the duration of solitary shock waves. We address the method in detail and present results of the modeling of the propagation of shock-associated extreme-ultraviolet (EUV) waves as well as Moreton waves along the solar surface in the simplest solar corona model. The calculations reveal deceleration and lengthening of the waves. In contrast, waves considered in the linear approximation keep their length unchanged and slightly accelerate.Comment: 15 pages, 7 figures, accepted for publication in Solar Physic