The Eskom East Grid Traction Network (EGTN) supplying traction loads and distribution networks has experienced at least one surge arrester failure over the past ten years. These failures results in poor network reliability and customer dissatisfactions which are often overlooked. This is because reliability indices used in the reliability evaluation of transmission and distribution networks are different. It is suspected that fast transient faults in this network initiate system faults leading to surge arrester design parameter exceedances and poor network insulation coordination. Preliminary investigations in network suggest that transient studies were not done during network planning and design stages. This may have resulted in the lack of surge arrester parameter evaluations under transient conditions leading to improper surge arresters being selected and installed in this network resulting in surge arrester failures that are now evident. These failures may also have been exacerbated by the dynamic nature of traction loads as they are highly unbalanced, have poor power factors and emit high voltage distortions. Poor in-service conditions such as defects, insulation partial discharges and overheating, bolted faults in the network and quality of supply emissions can also contribute to surge arrester failures. To address problems arising with different reliability indices in these networks the reliability of the EGTN is evaluated. In this work the reliability evaluation of the EGTN is done by computing common distribution reliability indices using analytic and simulation methods. This is done by applying the analytic method in the EGTN by assessing network failure modes and effects analysis (FMEA) when the surge arrester fails in this network. The simulation method is applied by applying and modifying the MATLAB code proposed by Shavuka et al. [1]. These reliability indices are then compared with transmission reliability indices over the same period. This attempts to standardize reliability evaluations in these networks. To assess the impact of transient faults in the surge arrester parameter evaluation the EGTN is modelled and simulated by initiating transient faults sequentially in the network at different nodes and under different loading conditions. This is done by using Power System Blockset (PSB), Power System Analysis Toolbox (PSAT) and Alternate Transient Program (ATP) simulation tools and computing important surge arrester parameters i.e. continuous operating voltage, rated voltage, discharge current and energy absorption capability (EAC). These parameters are assessed by in the EGTN by evaluating computed surge arrester parameters against parameters provided by manufacturers, the Eskom 88 kV surge arrester specification and those parameters recommended in IEC 60099-4. To assess the impact and contribution of in-service conditions, faults and quality of supply emissions in surge arrester failures these contributing factors are investigated by assessing infra-red scans, fault analysis reports, results of the sampled faulted surge arrester in this network and quality of supply parameters around the time of failures. This study found that Eskom transmission and distribution network reliability indices can be standardized as distribution reliability indices i.e. SAIDI, SAIFI, CAIDI, ASAI and ASUI indices are similar to Eskom transmission indices i.e. SM, NOI, circuit availability index and circuit unavailability index respectively. Transient simulations in this study showed that certain surge arresters in the EGTN had their rated surge arrester parameters exceeded under certain transient conditions and loading conditions. These surge arresters failed as their discharge currents and EACs were exceeded under heavy and light network loading conditions. This study concluded that surge arresters whose discharge currents and EACs exceeded were improperly evaluated and selected prior to their installations in the EGTN. This study found the EAC to be the most import parameter in surge arrester performance evaluations. The Eskom 88 kV surge arrester specification was found to be inadequate, inaccurate and ambiguous as a number of inconsistencies in the usage of IEEE and IEC classified systems terminology were found. It was concluded that these inconsistencies may have led to confusions for manufacturers during surge arrester designs and selections in the EGTN. The evaluation of fault reports showed that two surge arrester failures in this network were caused by hardware failures such as conductor failure and poor network operating as the line was continuously closed onto a fault. There was no evidence that poor in-service and quality of supply emissions contributed to surge arrester failures in this network. PSB, PSAT and ATP simulation tools were found adequate in modelling and simulating the EGTN. However the PSB tool was found to be slow as the network expanded and the PSAT required user defined surge arrester models requiring detailed manufacture data sheets which are not readily available. ATP was found to be superior in terms of speed and accuracy in comparison to the PSB and PSAT tools. The MATLAB code proposed by Shavuka et al. [1] was found to be suitable and accurate in assessing transmission networks as EGTN's reliability indices computed from this code were comparable to benchmarked Eskom distribution reliability indices. The work carried out in this research will assist in improving surge arrester performance evaluations, the current surge arrester specification and surge arrester selections. Simulation tools utilized in this work show great potential in achieving this. Reliability studies conducted in this work will assist in standardizing reliability indices between Eskom's transmission and distribution divisions. In-service condition assessment carried out in this work will improve surge arrester condition monitoring and preventive maintenance practices.

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An annoying tonal noise is produced by modern electrical trains duringacceleration and deceleration. This noise is caused by electromagneticforces generating structural vibrations, especially from the traction motors.The electromagnetic noise is dominant at low train speeds and affectsboth the passengers on the train and on platforms, as well as peopleliving near the track. The focus on this issue has increased the last years,both regarding legislation, contractual requirements and also because ofexpectations from citizens and travelers. To be able to design low noiseelectric drive systems, a thorough understanding of the cause and thepossibility to predict the electromagnetic noise is needed. This thesisdescribes the modelling and simulation of an complete multi-physicsreal-time environment for prediction and analysis of the electromagneticnoise. The simulation results are validated against measurements of thestructural vibration and acoustic response of a real traction motor fed bya power converter running in the entire operational range. / <p>QC 20161118</p>

Yes / GFRP profiled-concrete composite beams with groove shear connectors are analyzed using finite the element (FE) analysis. The concrete damaged plasticity (CDP) model was adopted for normal strength concrete (NSC) and reactive powder concrete (RPC). The orthotropic behaviour of GFRP profile was taken into consideration, and the bi-linear traction-separation model was used to investigate the bond-slip behavior between GFRP profile and concrete. Furthermore, parametric studies were conducted to investigate the effects of strength and the cross-sectional dimensions of concrete, strength (orthotropy), and the cross-sectional dimensions (the web height and the thickness of FRP plate). Numerical analysis results correlate well with experimental results. Based on numerical analysis, the composite beam with shear connectors spacing at 100 mm has a deflection-limit load of 21.4 % higher than the specimens with 150 mm spacing. It is possible to improve the bonding behavior of interfaces by using groove shear connectors. The ultimate load and deformation, and pseudo-ductility were significantly improved by using RPC with high strength and toughness (ultimate compressive strain). GFRP profiles with greater orthotropy coefficients provide fully utilized concrete's compressive strength, preventing premature crushing and enhancing composite structure stiffness. Flexural performance of the composite beams can be improved efficiently by choosing the appropriate sectional size during design and construction. / The authors would like to thank the financial support provided by the Natural Science Foundation of Jiangsu Province, China (BK20201436), the Science and Technology Project of Jiangsu Construction System (2018ZD047, 2021ZD06), the Science and Technology Project of Gansu Construction System (JK2021-19), the Open Foundation of Jiangsu Province Engineering Research Center of Prefabricated Building and Intelligent Construction (2021), the High-End Foreign Experts Project of Ministry of Science and Technology, China (G2022014054L), the Science and Technology Cooperation Fund Project of Yangzhou City and Yangzhou University (YZU2022194, YZU212105), the Blue Project Youth Academic Leader of Colleges and Universities in Jiangsu Province (2020), the Science and Technology Project of Yangzhou Construction System (2022ZD03, 202204) and the Technology Innovation Cultivation Fund of Yangzhou University (2020-65).

This thesis intends to utilize biomechanics to study the endothelial biomechanical response in a static hyperglycemic microenvironment. Hyperglycemia is a diabetic condition with abnormally high levels of glucose in the bloodstream. The effects of hyperglycemia over time lead to vascular complications resulting in patients being more prone to cardiovascular diseases. Current studies have focused on the molecular mechanisms affected by hyperglycemia; however, the mechanical mechanisms by which hyperglycemia causes vascular structural and functional changes are understudied. Therefore, to study the effects of hyperglycemia in the endothelium, Human Umbilical Vein Endothelial Cells (HUVEC) were cultured under three glucose conditions: normal glucose (4 mmol/l D-glucose), high glucose (30 mmol/l D-glucose), and an osmotic control (4 mmol/l D-glucose + 26 mmol/l D-mannitol). To evaluate the biomechanical response, we used traction force microscopy and monolayer stress microscopy to measure the cell-substrate tractions and cell-cell intercellular stresses. For the RMS tractions, HUVEC monolayers exposed to high glucose decreased by 10%, while the osmotic control decreased by 17% compared to the normal glucose. HUVEC monolayers exposed to high glucose produced average normal stresses that were 53% lower than monolayers exposed to normal glucose, while the osmotic control decreased by 51% compared to the normal glucose. For the maximum shear stresses, HUVEC monolayers exposed to high glucose decreased by 20%, while the osmotic control decreased by 14% compared to the normal glucose. To conclude this study, we report that hyperglycemia lowers the biomechanical response in the endothelium compared to normal glucose conditions. These results will contribute to understanding the specific role hyperglycemia has on endothelial mechanics and its role in the progression and development of cardiovascular diseases in diabetic patients.

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The world is continually changing towards more energy efficient alternatives and less pollution. For the traction market, electric powertrains have become the go-to method, superior to both steam and diesel-electric hybrid systems. For subways and trams the natural development now is towards smaller motors with high power output, the goal is to use as much space as possible for the passengers and keep the performance of a larger motor setup. One problem with increasing the power density of the motors is that the accumulated heat from losses also increases per volume. All motors have different efficiency and different limits on temperatures in different parts. For this project a closed, self-ventilated traction motor with axis height 250mm (CSV250) was evaluated. The motor has an input power just above 140kW and the identified limiting factor is the temperature of the bearings, specifically the front bearing located at the fan side of the motor.   An already existing and partly validated ANSYS MotorCAD model was used for full system overview and as a guide to build a COMSOL Multiphysics model of the motor rotor. The COMSOL model could be effectively changed to represent different configurations of the solution. The COMSOL solver is based on the finite element method, FEM, whereas the MotorCAD model is built as a thermal network with lumped parameter method, LPM.    The proposed solution to the high temperature is implementation of heat-pipes in strategic positions. This project only contains evaluation of heat-pipes positioned in the center of the shaft deployed in three different configurations: a short heat-pipe transferring heat from the bearing to the fan, a long heat-pipe transferring heat from the active rotor parts to the fan and a long heat-pipe similar to previous case but with the heat-pipe insulted at the bearing section. The simulations yield performance specifications for the solution design that will give the expected result, complemented with theory this can then give the full appliable solution to the specified problem.   For the short heat-pipe case a decrease in temperature form 116.5 to 96.5°C was achieved in the front bearing by increasing the heat-transfer from the bearing towards the fan with 84.4W. This is well under the preferred temperature of maximum 110°C. In the long heat-pipe case a total of 360W was dispersed through the fan and this lowered the highest temperature point in the rotor from 172.2 to 160.8°C but with the negative effect of increasing the temperature of the front bearing. In the third case the insulation of the long heat-pipe in the bearing section managed to lower this increased temperature from 130.4 to 122.4°C while 360W were still transferred through to the fan. This is under the absolute maximum at 130°C but over 110°C. The results point towards the possibility to increase power density and keeping temperatures manageable using heat-pipes but further work and experiments is needed to prov the concept.