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In this paper, mechanical stresses on railway traction line insulators are analyzed by structural analysis. In application of railway traction lines, insulators are not only used to insulate but also subjected to adverse environmental conditions and mechanical vibrations. Two kinds of test to verify the robustness of insulators are performed in this study. Cantilever load test and tensile force test are carried out to ensure the reliability and stability of railway traction line insulators. Structural analysis that focuses on cantilever load test and tensile force test is carried out by using COM

Solid insulation materials are mainly used in superconducting magnet electrical applications. Such insulation must not only have the desired mechanical properties but also electrical properties under cryogenic conditions. Glassfiber-reinforced polymer (GFRP) needs to be studied with respect to its cryogenic insulation properties in relation to alternating current voltages with the current at maximum power (AC, Imp) (Kwang et al. , 2007). A voltage lower than that at which dielectric breakdown occurs leads to creepage discharge, which causes the dielectric strength to decrease and results in electrical accidents; therefore, we need to study the properties of creepage discharge. In this paper, we present the results of experiments on the properties of creepage discharge inside GFRP with gaseous (GN2) and liquid (LN2) nitrogen (Bansal et al. , 2008). The experimental results showed that the creepage discharge voltage increased with increasing creepage distance and pressure under LN2 and GN2 conditions (Hwang et al. , 2012). In addition, the creepage discharge electric field value was confirmed by FEM analysis. We checked the safety factor through simulation to apply the outcome of these experiments to the design of electrical applications.

The termination part of a high temperature superconducting apparatus such as a superconducting fault current limiter or a superconducting cable is usually insulated by pressurized SF 6 gas for its excellent dielectric strength. However, SF 6 condenses into LN 2 because of its high boiling point (approximately 209 K) during operation. The condensed SF 6 into LN 2 may result in problems such as dielectric degradation and system pressure decline. In order to prevent the condensation of SF 6 into LN 2 , the termination of an HTS apparatus is divided into two parts by using a spacer: an upper part pressurized by SF 6 with room temperature and a lower part pressurized by GN 2 with cryogenic temperature. The termination part should be operated in a high-pressure condition in order to ensure safe dielectric characteristics of HTS apparatuses. In this paper, dielectric characteristics as well as mechanical characteristics of a spacer under pressurized gas are conducted. It is well known that electrical breakdown may occur in the form of creepage discharge along the surface of a solid material rather than in the form of penetration sparkover through a solid or gaseous material. Experiments on the creepage discharge characteristics according to several solid materials under various pressures are conducted and a computer simulation using a finite element method is performed to analyze electric field distribution and mechanical strength of a spacer. Finally, the specifications of a spacer for 154 kV superconducting fault current limiters such as diameter, thickness, shape, and material, are suggested according to various safety factors.

Solid insulation materials need to be robust in terms of both mechanical and electrical performance for application in a high-voltage superconducting apparatus. It is known that creepage discharge characteristics of solid insulation materials are inferior to their electrical breakdown characteristics with penetration. Therefore, electrical breakdown accidents in a superconducting apparatus could occur as a form of creepage discharge rather than electrical breakdown with penetration. In this study, we conduct dielectric experiments on the penetration and creepage discharge characteristics of epoxy resin and polypropylene laminated paper under cryogenic temperature by using three kinds of electrode systems. The first is for creepage discharge experiments along the surfaces of solid insulation materials in liquid nitrogen. The second is for creepage discharge experiments across the interface between two different solid insulation materials making contact in liquid nitrogen. The third is for experiments of electrical breakdown with penetration on solid insulation materials in liquid nitrogen. Dielectric experiments are conducted with an absolute pressure of 0.1 MPa under alternating current and lightning impulse voltages. Experimental results for electrical breakdown characteristics of solid insulation materials with penetration are compared with the creepage discharge characteristics on the surface and interfaces between solid insulation materials. Moreover, the criteria for electric field intensities at creepage discharge voltages in various conditions are deduced as empirical formulas.

Background Previous studies suggest the presence of attentional bias towards suicide-relevant information in suicidal individuals. However, the findings are limited by their reliance on behavioral measures. This study investigates the role of difficulty in disengaging attention from suicide-relevant stimuli using the P300 component of event-related potentials (ERPs). Methods Forty-four adults with Major Depressive Disorder (MDD) were administered the spatial cueing task using suicide-relevant and negatively-valenced words as cue stimuli. Disengagement difficulty was measured using reaction time and P300 during invalid trials. Results P300 amplitudes at Pz were higher in suicide-relevant compared to negatively-valenced word condition on invalid trials for participants with low rates of suicidal behavior. However, no such difference was found among participants with high rates of suicidal behavior. P300 amplitudes for suicide-relevant word condition were negatively correlated with “lifetime suicide ideation and attempt” at Pz. No significant results were found for the reaction time data, indicating that the ERP may be more sensitive in capturing the attentional disengagement effect. Limitations The groups were divided according to Suicidal Behaviors Questionnaire-Revised (SBQ-R) total score. Neutral stimulus was not included as cue stimuli. Most participants were under medication during the experiment. Conclusions Our results indicate that patients with MDD and low rates of suicidal behavior show difficulty in disengaging attention from suicide-relevant stimuli. We suggest that suicide-specific disengagement difficulties may be related to recentness of suicide attempt and that acquired capability for suicide may contribute to reduced disengagement difficulties.

Superconducting cables are one of the most promising applications among several high voltage superconducting power apparatuses owing to its low energy loss and high power capacities. Superconducting cables system consists of four parts: the termination, the joint box, the core, and the cooling system. The core is responsible for power transport, and is insulated with polypropylene laminated paper (PPLP) to ensure a high dielectric strength in the presence of liquid nitrogen (LN 2 ). The insulation layer of the core is fabricated by winding PPLP in multiple layers. It is inevitable that butt gap filled with LN 2 is generated in this process. Currently, many studies on the dielectric characteristics of PPLP according to various intervals between butt gap under 0.1 MPa and those with fixed butt gap according to various pressures have been conducted. A study on determining a proper interval between butt gap according to pressure in order to develop reliable superconducting cables under high pressure should be performed because superconducting cables system in power grid is operated under high pressure. This study focuses on the evaluation of the dielectric characteristics of PPLP with interval between butt gap at various pressures. In addition, dielectric experiments on V-t characteristics for a mini-model cable are conducted and experimental results are analyzed by the inverse power model.