Abstract:To reduce the probability of such flashover accidents caused by bird droppings， a new type of insulated coated drainage line was developed. This line utilized high-performance silicone rubber insulating materials to fully coat the steel-cored aluminum strand， and an umbrella skirt was installed on the surface of the drainage line. Simulation analysis was conducted to examine the influence of the silicone rubber insulation layer and bird droppings on the spatial electric field distribution of the drainage line. The flashover characteristics of insulated coated drainage lines against bird droppings were studied by simulation test. The simulation results show that with the increase of the thickness of the insulating layer， the surface electric field intensity decreases gradually. As the thickness of the semiconductor layer increases， the electric field intensity on the surface of the drainage line decreases. The test results show that the insulation layer coated by bare wire can significantly improve the insulation performance of the drainage line， and the silicone rubber insulation coating is obviously better than the buckled silicone rubber insulation sheath. Every 1 mm increase in the thickness of the silicone rubber insulation layer results in breakdown voltage increases of about 10.7 kV， and the semiconductor layer can further improve the insulation performance. The umbrella skirt can effectively prevent the spread of the arc on the surface of the insulated coated drainage line.

Abstract:This paper proposes a method to characterize the spatial electric field distributions of long rod-plane and sphere-plane gaps. The finite element simulation result of the electric field was post-processed， and 66 feature quantities were extracted from the interelectrode path and a conical region. A prediction model was established based on the least squares support vector machine （LS-SVM）， taking the electric field distribution feature set and the discharge voltage as input and output parameters. The improved grey wolf optimizer was used to optimize the model parameters， and the feature dimension was reduced by the maximal information coefficient method. This model was applied to predict the standard switching impulse discharge voltages of long rod-plane and sphere-plane gaps. The results of the case study indicate that the predicted values of test samples are in good agreement with the experimental values， with a maximum relative error of 8.3% and the mean absolute percentage error of 3.2%. This study can provide references for air gap insulation calculation.

Abstract:The surrounding electromagnetic fields will be changed greatly when the track of medium and low speed maglev is electrified. The generated effect of strong electromagnetic field has a great impact on the safety of the pushing and falling of the steel box girder over the maglev track.Therefore，taking the construction of Changsha Huanghua International Airport Avenue Project as a practical case，the impact of electromagnetic field on the pushing and falling of the steel box girder over the maglev track is studied.The large finite element analysis software ANSOFT is used to perform finite element analysis and numerical calculation on the strong electromagnetic field of the maglev track.It is assumed that the current of the maglev track remains constant during the advancement of the steel box girder. By changing the position of the steel box girder relative to the track，the impact of the strong electromagnetic field generated by the maglev track on the launching and falling of the steel box girder under the different working conditions is studied. After performing the static analysis and calculation for each working condition，the corresponding construction safety scope is obtained. The conclusion of the study provides references and suggestions for similar projects in the future.

Abstract:In this work, the dielectric functionally graded material (ε-FGM) was initially employed to improve the electric field distribution along spacer surface. Taking the permittivity distribution as the object, a global optimization algorithm was proposed in this paper, which usesd the maximum electric stress as a feedback to update the permittivity distribution. Using the APDL language incorporated in ANSYS combined with MATLAB, the influences of step length and layer number on the field were studied. The results show that the electric stress along spacer surface becomes smoother with the decrease of step length and the increase of iteration number. Correspondingly, the permittivity range is significantly enlarged. The high electric field area of spacer is shifted from the electrode and triple junction to the middle part, and the utilization ratio along the lower and upper surface reaches 0.75. The results provide useful references for spacer design.

Abstract:This paper investigated the discharging mechanism of dry-type transformer by analyzing the outside insulation surface electric-field distribution of a 10kV epoxy resin cast dry-type transformer. Firstly, the 2-D finite element model was established,and on this basis the surface electric-field distributions were analyzed under two operating environments of the dry outside insulation surface and the external insulation surface with wetting layer. The results have indicated that the local electric-field density of external insulation surface rises nearly ten times compared with the dry external surface, which is easy to cause the creeping discharging phenomenon and poses a threat to external insulation. A type of low surface energy coating was used on the transformer to prevent the surface discharging phenomenon, and the electric-field distribution was analyzed when the coating surface was covered with dispersed water drops. Compared with the above results, it is obvious that the surface electric-field density decreases eighty percent, which can effectively increase the life of the epoxy resin cast dry-type transformer.

Abstract:Taking single layer poly (p phenylene vinylene)(PPV)thin film light emitting diodes (LEDs) as example,the electric field distribution in PPV thin film and its effect on injection,transportation and combination of carriers are investigated.It helps to b