With the continuous progress of society, the level of national economy has been greatly improved, and the process of urbanization has been accelerated. Electric power is the main basic energy in our country, has been ...With the continuous progress of society, the level of national economy has been greatly improved, and the process of urbanization has been accelerated. Electric power is the main basic energy in our country, has been an indispensable energy for social and economic development, and plays an important role in people's daily production and life. However, due to various factors, distribution and electrical engineering can lead to the loss of wires, thus affecting the improvement of power quality. This paper first analyzes the causes of line loss in transmission and distribution engineering, and then further discusses the key points of line loss management in transmission and distribution engineering.展开更多
The purpose of this paper is to clarify the importance of line loss management based on electricity information acquisition system, and put forward some targeted strategies to promote line loss management. The continu...The purpose of this paper is to clarify the importance of line loss management based on electricity information acquisition system, and put forward some targeted strategies to promote line loss management. The continuous development of science and technology provides an opportunity for the renewal of electricity information acquisition system, and the management of line loss in station area has been improved. However, from the current situation, the implementation of line loss management in the station area has not achieved the desired effect, and is not satisfactory, which has caused obstacles to the further development of enterprises. This paper mainly expounds the situation and problems of line loss management in power information collection and carries on the corresponding analysis, and puts forward several suggestions to promote the management of line loss in the station, which further promotes the management work.展开更多
Through the continuous development of the acquisition system, the line loss management of the station has been constantly improved. However, due to the influence of various factors, the effect of line loss management ...Through the continuous development of the acquisition system, the line loss management of the station has been constantly improved. However, due to the influence of various factors, the effect of line loss management in station area is not ideal, which brings some problems to the development of the company. This paper analyzes and studies the actual situation of the electricity information acquisition system, the influencing factors of line loss control in the station area, the causes of abnormal line loss in the station area, and the management countermeasures of line loss in the station area based on the electricity information acquisition system.展开更多
Focused on the challenges raised by the largescale integration of renewable energy resources and the urgent goal of energy saving,a novel control scheme for the unified power flow controller(UPFC)series converter is p...Focused on the challenges raised by the largescale integration of renewable energy resources and the urgent goal of energy saving,a novel control scheme for the unified power flow controller(UPFC)series converter is proposed to achieve line loss reduction and security enhancement in distribution systems with a high penetration of renewable energy.Firstly,the line loss minimum conditions of a general distribution system with loop configurations are deduced.Secondly,security constraints including the permissible voltage range,the line loading limits and the UPFC ratings are considered.System security enhancement with the least increase in line loss is tackled by solving a much reduced optimal power flow(OPF)problem.The computational task of the OPF problem is reduced by deducing the security-constrained line loss minimum conditions and removing the equality constraints.Thirdly,a hybrid control scheme is proposed.Line loss minimization is achieved through a dynamic controller,while an OPF calculator is integrated to generate corrective action for the dynamic controller when the security constraints are violated.The validity of the proposed control strategies is verified in a modified IEEE 33 bus test system.展开更多
A magnetically insulated transmission line （MITL） is used to transmit high power electric pulses in large pulse power systems. However, current loss is unavoidable, especially when the current density is up to 1 MA/...A magnetically insulated transmission line （MITL） is used to transmit high power electric pulses in large pulse power systems. However, current loss is unavoidable, especially when the current density is up to 1 MA/cm. In the paper, the current loss of an MITL made of stainless steel, which is usually used in large pulse power generators, is experimentally studied, and possible mechanisms to explain the current loss of the MITL are analyzed and discussed. From the experimental results, the relationship between loss current density and input current density follows approximately a power law. The loss is also related to the configuration of the MITL.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
In the present paper, to build model of two-line queuing system with losses GI/G/2/0, the approach introduced by V.S. Korolyuk and A.F. Turbin, is used. It is based on application of the theory of semi-Markov processe...In the present paper, to build model of two-line queuing system with losses GI/G/2/0, the approach introduced by V.S. Korolyuk and A.F. Turbin, is used. It is based on application of the theory of semi-Markov processes with arbitrary phase space of states. This approach allows us to omit some restrictions. The stationary characteristics of the system have been defined, assuming that the incoming flow of requests and their service times have distributions of general form. The particular cases of the system were considered. The used approach can be useful for modeling systems of various purposes.展开更多
Background and Objective It has been proven that copy number gain/or loss (copy number variation CNV) in uences gene expression and result in phenotypic variation by
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
文摘With the continuous progress of society, the level of national economy has been greatly improved, and the process of urbanization has been accelerated. Electric power is the main basic energy in our country, has been an indispensable energy for social and economic development, and plays an important role in people's daily production and life. However, due to various factors, distribution and electrical engineering can lead to the loss of wires, thus affecting the improvement of power quality. This paper first analyzes the causes of line loss in transmission and distribution engineering, and then further discusses the key points of line loss management in transmission and distribution engineering.
文摘The purpose of this paper is to clarify the importance of line loss management based on electricity information acquisition system, and put forward some targeted strategies to promote line loss management. The continuous development of science and technology provides an opportunity for the renewal of electricity information acquisition system, and the management of line loss in station area has been improved. However, from the current situation, the implementation of line loss management in the station area has not achieved the desired effect, and is not satisfactory, which has caused obstacles to the further development of enterprises. This paper mainly expounds the situation and problems of line loss management in power information collection and carries on the corresponding analysis, and puts forward several suggestions to promote the management of line loss in the station, which further promotes the management work.
文摘Through the continuous development of the acquisition system, the line loss management of the station has been constantly improved. However, due to the influence of various factors, the effect of line loss management in station area is not ideal, which brings some problems to the development of the company. This paper analyzes and studies the actual situation of the electricity information acquisition system, the influencing factors of line loss control in the station area, the causes of abnormal line loss in the station area, and the management countermeasures of line loss in the station area based on the electricity information acquisition system.
文摘Focused on the challenges raised by the largescale integration of renewable energy resources and the urgent goal of energy saving,a novel control scheme for the unified power flow controller(UPFC)series converter is proposed to achieve line loss reduction and security enhancement in distribution systems with a high penetration of renewable energy.Firstly,the line loss minimum conditions of a general distribution system with loop configurations are deduced.Secondly,security constraints including the permissible voltage range,the line loading limits and the UPFC ratings are considered.System security enhancement with the least increase in line loss is tackled by solving a much reduced optimal power flow(OPF)problem.The computational task of the OPF problem is reduced by deducing the security-constrained line loss minimum conditions and removing the equality constraints.Thirdly,a hybrid control scheme is proposed.Line loss minimization is achieved through a dynamic controller,while an OPF calculator is integrated to generate corrective action for the dynamic controller when the security constraints are violated.The validity of the proposed control strategies is verified in a modified IEEE 33 bus test system.
基金supported by National Natural Science Foundation of China(No.10905047)
文摘A magnetically insulated transmission line （MITL） is used to transmit high power electric pulses in large pulse power systems. However, current loss is unavoidable, especially when the current density is up to 1 MA/cm. In the paper, the current loss of an MITL made of stainless steel, which is usually used in large pulse power generators, is experimentally studied, and possible mechanisms to explain the current loss of the MITL are analyzed and discussed. From the experimental results, the relationship between loss current density and input current density follows approximately a power law. The loss is also related to the configuration of the MITL.
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.
文摘In the present paper, to build model of two-line queuing system with losses GI/G/2/0, the approach introduced by V.S. Korolyuk and A.F. Turbin, is used. It is based on application of the theory of semi-Markov processes with arbitrary phase space of states. This approach allows us to omit some restrictions. The stationary characteristics of the system have been defined, assuming that the incoming flow of requests and their service times have distributions of general form. The particular cases of the system were considered. The used approach can be useful for modeling systems of various purposes.
基金supported by a grant from the key project of the National Natural Science Foundation of China (to Qinghua ZHOU)(No. 30430300)National Natural Science Foundation of China (to Qinghua ZHOU)(No. 30670922)INTERNATION Scienc and Techniquie COOPRATION PROGRAM OF CHINA (ISCP) (to Qinghua ZHOU)(No.2006DFB32330)
文摘Background and Objective It has been proven that copy number gain/or loss (copy number variation CNV) in uences gene expression and result in phenotypic variation by
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.
