<div style="text-align:justify;"> <span style="font-family:Verdana;">A graph is said to be cordial if it has 0 - 1 labeling which satisfies particular conditions. In this paper, we cons...<div style="text-align:justify;"> <span style="font-family:Verdana;">A graph is said to be cordial if it has 0 - 1 labeling which satisfies particular conditions. In this paper, we construct the corona between paths and second power of fan graphs and explain the necessary and sufficient conditions for this construction to be cordial.</span> </div>展开更多
An anti-corona method for the power transmission lines is proposed in this paper. The RTV coating is used as the anti-corona coating, which is spaying onto the surface of the wearing conductor. The corona characterist...An anti-corona method for the power transmission lines is proposed in this paper. The RTV coating is used as the anti-corona coating, which is spaying onto the surface of the wearing conductor. The corona characteristic of the conductor test was done, and the corona onset voltage increase after the spraying of the anti-corona layer, the corona loss in the same voltage decrease, which could prove the excellent effect of improving the corona characteristic of the conductor. This anti-corona method will have great prospect, based on the background of the construction of UHV power transmission lines.展开更多
The classical minimization of power losses in transmission lines is dominated by artificial intelligence techniques, which do not guarantee global optimum amidst local minima. Revolutionary and evolutionary techniques...The classical minimization of power losses in transmission lines is dominated by artificial intelligence techniques, which do not guarantee global optimum amidst local minima. Revolutionary and evolutionary techniques are encumbered with sophisticated transformations, which weaken the techniques. Power loss minimization is crucial to the efficient design and operation of power transmission lines. Minimization of losses is one way to meet steady grid supply, especially at peak demand. Thus, this paper has presented a gradient technique to obtain optimal variables and values from the power loss model, which efficiently minimizes power losses by modifying the traditional power loss model that combines Ohm and Corona losses. Optimality tests showed that the unmodified model does not support the minimization of power losses on transmission lines as the Hessian matrix portrayed the maximization of power losses. However, the modified model is consistent with the gradient method of optimization, which yielded optimum variables and values from the power loss model developed in this study. The unmodified (modified) models for Bujagali-Kawanda 220 kV and Masaka West-Mbarara North 132 kV transmission lines in Uganda showed maximum power losses of 0.406 (0.391) and 0.452 (0.446) kW/km/phase respectively. These results indicate that the modified model is superior to the unmodified model in minimizing power losses in the transmission lines and should be implemented for the efficient design and operation of power transmission lines within and outside Uganda for the same transmission voltages.展开更多
An improved method for calculating the corona power loss and the ground-level electric field on HVAC transmission lines induced by corona is proposed.Based on a charge simulation method combined with a method of succe...An improved method for calculating the corona power loss and the ground-level electric field on HVAC transmission lines induced by corona is proposed.Based on a charge simulation method combined with a method of successive images,the proposed method has the number and location of the simulated charges not arbitrary.When the surface electric field of a conductor exceeds the onset value,charges are emitted from corona into the space around,and the space ions and the surface charges on each sub-conductor are simulated by using the images of the other sub-conductors.The displacements of the space ions are calculated at every time step during corona periods in both the positive and the negative half cycles.Several examples are calculated by using the proposed method,and the calculated electric field at the ground level and the corona power loss agree well with previous measurements.The results show that simulating 12 charges in each conductor during 600 time steps in one cycle takes less time while guarantees the accuracy.The corona discharge from a 220 kV transmission line enhances slightly(less than 2%) the electric field at the ground level,but this effect is little from a 500 kV line.The improved method is a good compromise between the time cost and the accuracy of calculation.展开更多
A new corona protection varnish was prepared by using epoxy/montmorillonite nanocomposite and pure epoxy resin as adhesives respectively.The adhesive with different amounts of organic montmorillonite（OMMT） was mixed...A new corona protection varnish was prepared by using epoxy/montmorillonite nanocomposite and pure epoxy resin as adhesives respectively.The adhesive with different amounts of organic montmorillonite（OMMT） was mixed with 1200 mesh silicon carbide（Si C） by different weight ratios.The surface states of the varnishes with various adhesives were observed by powerful optical microscope.Some properties of the varnishes were analyzed during the enduring time under 5kV/cm DC,such as the relation of change in nonlinear coefficient,natural surface resistivity,and surface temperature variation.The results showed that the amounts of OMMT had little effect on the natural surface resistance of the varnish but had important influence on the nonlinear property of the varnish.When the range of the OMMT content was 2wt% to 6wt%,the nonlinear coefficient of all materials with epoxy/OMMT nano-composite adhesive was higher than that with pure epoxy resin adhesive.The surface temperature of the varnish with epoxy/OMMT nanocomposite adhesive was all lower than that with the pure epoxy resin adhesive under high electrical field strength.展开更多
文摘<div style="text-align:justify;"> <span style="font-family:Verdana;">A graph is said to be cordial if it has 0 - 1 labeling which satisfies particular conditions. In this paper, we construct the corona between paths and second power of fan graphs and explain the necessary and sufficient conditions for this construction to be cordial.</span> </div>
文摘An anti-corona method for the power transmission lines is proposed in this paper. The RTV coating is used as the anti-corona coating, which is spaying onto the surface of the wearing conductor. The corona characteristic of the conductor test was done, and the corona onset voltage increase after the spraying of the anti-corona layer, the corona loss in the same voltage decrease, which could prove the excellent effect of improving the corona characteristic of the conductor. This anti-corona method will have great prospect, based on the background of the construction of UHV power transmission lines.
文摘The classical minimization of power losses in transmission lines is dominated by artificial intelligence techniques, which do not guarantee global optimum amidst local minima. Revolutionary and evolutionary techniques are encumbered with sophisticated transformations, which weaken the techniques. Power loss minimization is crucial to the efficient design and operation of power transmission lines. Minimization of losses is one way to meet steady grid supply, especially at peak demand. Thus, this paper has presented a gradient technique to obtain optimal variables and values from the power loss model, which efficiently minimizes power losses by modifying the traditional power loss model that combines Ohm and Corona losses. Optimality tests showed that the unmodified model does not support the minimization of power losses on transmission lines as the Hessian matrix portrayed the maximization of power losses. However, the modified model is consistent with the gradient method of optimization, which yielded optimum variables and values from the power loss model developed in this study. The unmodified (modified) models for Bujagali-Kawanda 220 kV and Masaka West-Mbarara North 132 kV transmission lines in Uganda showed maximum power losses of 0.406 (0.391) and 0.452 (0.446) kW/km/phase respectively. These results indicate that the modified model is superior to the unmodified model in minimizing power losses in the transmission lines and should be implemented for the efficient design and operation of power transmission lines within and outside Uganda for the same transmission voltages.
基金supported by National Basic Research Program of China(973 Program)(2011CB209404)
文摘An improved method for calculating the corona power loss and the ground-level electric field on HVAC transmission lines induced by corona is proposed.Based on a charge simulation method combined with a method of successive images,the proposed method has the number and location of the simulated charges not arbitrary.When the surface electric field of a conductor exceeds the onset value,charges are emitted from corona into the space around,and the space ions and the surface charges on each sub-conductor are simulated by using the images of the other sub-conductors.The displacements of the space ions are calculated at every time step during corona periods in both the positive and the negative half cycles.Several examples are calculated by using the proposed method,and the calculated electric field at the ground level and the corona power loss agree well with previous measurements.The results show that simulating 12 charges in each conductor during 600 time steps in one cycle takes less time while guarantees the accuracy.The corona discharge from a 220 kV transmission line enhances slightly(less than 2%) the electric field at the ground level,but this effect is little from a 500 kV line.The improved method is a good compromise between the time cost and the accuracy of calculation.
基金Funded by the Major State Basic Research Development Program of China(No.2010CB736208)the Planning Project of Hei Longjiang Province for Science and Technology(No.GC10A203)
文摘A new corona protection varnish was prepared by using epoxy/montmorillonite nanocomposite and pure epoxy resin as adhesives respectively.The adhesive with different amounts of organic montmorillonite（OMMT） was mixed with 1200 mesh silicon carbide（Si C） by different weight ratios.The surface states of the varnishes with various adhesives were observed by powerful optical microscope.Some properties of the varnishes were analyzed during the enduring time under 5kV/cm DC,such as the relation of change in nonlinear coefficient,natural surface resistivity,and surface temperature variation.The results showed that the amounts of OMMT had little effect on the natural surface resistance of the varnish but had important influence on the nonlinear property of the varnish.When the range of the OMMT content was 2wt% to 6wt%,the nonlinear coefficient of all materials with epoxy/OMMT nano-composite adhesive was higher than that with pure epoxy resin adhesive.The surface temperature of the varnish with epoxy/OMMT nanocomposite adhesive was all lower than that with the pure epoxy resin adhesive under high electrical field strength.
