324 research outputs found
Cryogenic Dielectrics and HTS Power Apparatus: Research at the University of Southampton
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The gender gap in early-career wage growth
No full textIn the UK the gender pay gap on entry to the labour market is approximately zero but ten years after labour market entry, there is a gender wage gap of almost 25 log points. This article explores the reason for this gender gap in early-career wage growth, considering three main hypotheses - human capital, job-shopping and 'psychological' theories. Human capital factors can explain about 11 log points, job-shopping about 1.5 log points and the psychological theories up to 4.5 log points depending on the specification. But a substantial unexplained gap remains: women who have continuous full-time employment, have had no children and express no desire to have them earn about 8 log points less than equivalent men after 10 years in the labour market. Copyright © The Author(s). Journal compilation © Royal Economic Society 2008.
The role of local labour market conditions and pupil attainment on post-compulsory schooling decisions
No full textThis paper assesses the role of local labour market conditions and pupil educational attainment as primary determinants of the post-compulsory schooling decision. Through the specification of a nested logit model the restrictive IIA assumption inherent in the multinomial logit (MNL) model is relaxed across multiple unordered outcomes. Our analysis shows that the factors influencing schooling decisions differ for males and females. For females, on average, the key drivers of the schooling decision are expected wage returns based on youth educational attainment, attitudes to school and parental aspirations, rather than local labour market conditions. However, for males, higher local unemployment rates encourage greater investment in education. The contribution of this paper to the existing literature is threefold. Firstly, a nested logit model is proposed as an alternative to a multinomial logit model (MNL). The former can formally incorporate the structured and sequential decision-making process that youths may engage with in relation to the post-compulsory schooling decision, as well as relaxing the restrictive IIA assumption inherent in the MNL across multiple unordered outcomes, an issue we discuss in more detail in our methodology section below. Secondly, the analysis is based on using extremely rich socioeconomic data from the LSYPE, matched to local labour market data and to administrative data from the National Pupil Database and Pupil Level Annual School Census (NPD/PLASC), which provide a broad set of unusually high-quality measures of prior attainment. We argue that such high-quality data and an appropriate model specification allows identification of the determinants of the post-compulsory decision in a more detailed manner than many previous analyses. Thirdly, the data has the scale necessary to consider whether the determinants of post compulsory schooling decisions vary by gender, a particularly important issue given the differential education participation rates of males and females (in this cohort, females are about 10 percentage points more likely to go on to higher education in the UK than males for example ), and the gendered choices of occupation (see, for example, Bertrand, 2011). Our work will therefore provide recent empirical evidence from England on gender differences in the determinants of education choices
Effects of modelling assumptions on the rating calculation for externally forced cooled high-voltage cables
No full textTo increase the rating of a high-voltage cable circuit the cable group can be externally forced cooled, using additional coolant pipes in proximity to the buried cable group. This complicates modelling of the heat transfer problem to obtain ratings as coolant temperature and therefore heat transfer coefficient varies along the cable route. The most common approach for obtaining the circuit rating is the finite difference (FD) method outlined in Electra 66. This method is computationally efficient and quick to solve. To investigate the assumptions underlying this approach and provide confidence over a range of model parameters, this paper presents the development of an extended 2-D heat-transfer finite element method (FEM) model. The ratings of two cable circuits have been modelled using this approach and are compared with results from Electra 66. Cable ratings from the two methods are consistent in trend but offset favourably by 2.6% using the FEM model for all burial depths tested. With the FEM model verified for standard assumptions the model provides a useful tool for rapid investigation of sensitivity to model assumptions. A sensitivity analysis to changes in ac resistance, burial depth, dielectric loss, soil thermal resistivity and surface boundary condition is presented
Condition Monitoring of Power Cables
No full textA National Grid funded research project at Southampton has investigated possible methodologies for data acquisition, transmission and processing that will facilitate on-line continuous monitoring of partial discharges in high voltage polymeric cable systems. A method that only uses passive components at the measuring points has been developed and is outlined in this paper. More recent work, funded through the EPSRC Supergen V, UK Energy Infrastructure (AMPerES) grant in collaboration with UK electricity network operators has concentrated on the development of partial discharge data processing techniques that ultimately may allow continuous assessment of transmission asset health to be reliably determined
Application of Finite Element Analysis to externally forced water cooled cable circuit ratings
No full textIn order to increase the available current carrying capacity of high voltage cables, utilities may employ forced water cooling within power transmission networks to remove the heat from cable groups. For example the transmission network of England and Wales includes externally forced cooled circuits, i.e. cooled by pumping water through pipes buried in the vicinity of high voltage transmission cables. At the present time a simple and expedient computer program is used to rate these circuits. This model is similar to that of Electra 66. To attribute confidence limits to cable ratings attained using this method an extended 2-D heat-transfer FEA model has been constructed to allow the calculation of the cable core temperature for a typical water-cooled three-phase circuit of three singlecore cables buried in flat horizontal arrangement within a backfilled trough. A sensitivity analysis of the model to changes in ac resistance, burial depth, dielectric loss, soil thermal resistivity and surface boundary condition has been performed and is presented
Thermal Bubble Dynamics in Cryogenic Liquids under Non-Uniform Electric Fields on Superconducting Power Apparatus
No full textThermal Bubble Behaviour in Liquid Nitrogen between Inclined Plane Electrodes
No full textThis paper describes an experimental study of the behaviour of thermally nucleated bubbles in liquid nitrogen between inclined plane-plane electrodes with an angle of 21°. Observation of the bubble motion captured using a camera at 1000 fps shows that bubble’s rising motion due to buoyancy is impeded by the application of dc electric field and gradient force. Bubbles are observed to collect at the top of the inclined plane electrodes, the closest point. The gas vapour of successive bubbles coalesces forming a large volume bubble which partially bridges the electrode gap. To better understand the forces experienced by the bubbles the competing gradient and buoyancy forces are analysed and presented
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