In order to study the effect of AC aging on space charge characteristics of low-density polyethylene (LDPE) films, an AC electric field of 50 kV/mm (peak value) was adopted for the accelerated aging test and space cha...
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ISBN:
(纸本)9781538653937
In order to study the effect of AC aging on space charge characteristics of low-density polyethylene (LDPE) films, an AC electric field of 50 kV/mm (peak value) was adopted for the accelerated aging test and space charge measurements of AC aged LDPE films were carried out subsequently. The results show that no significant space charge accumulation in the LDPE samples aged under a 50 kV/mm AC electric field. It can be seen that a significant positive space charge accumulation occurs inside the sample, when DC electric fields were applied to the AC aged LDPE samples. The long-term AC aging also causes more and deeper cracks on the surface of LDPE samples. Moreover, AC aging promotes the oxidation reaction of LDPE. The longer the aging time, the higher the degree of oxidation. On this basis, the probable relationship between space charge characteristics and material physicochemical properties of LDPE during AC electrical aging is clarified.
keyequipment or vulnerable equipment always intensify the development of cascading failure, so it is of great importance but also challenging to find them. Recent researches present the ranking of vulnerable equipmen...
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keyequipment or vulnerable equipment always intensify the development of cascading failure, so it is of great importance but also challenging to find them. Recent researches present the ranking of vulnerable equipment according to complex network theory, while lacking the information of system risk. In this paper, we explore the relationship between system risk and vulnerable equipment as well as the relationship between equipment, we puts forward an approximate equation of failure propagation based on the correlation matrix, and draw the conclusion that the probability of initial failure and the max-eigenvalue of correlation matrix determine the propagation of cascading failure. Extensive simulation results show the positive correlation between blackout risk and max-eigenvalue of correlation matrix when initial failure probability is fixed. And top 10 vulnerable equipment, which has higher Page Rank value, also has bigger value among the eigenvector of the max-eigenvalue. Furthermore, this paper analyzes the role of vulnerable equipment identified by Page Rank and Electric Betweenness methods, using the cascading failure simulation. The results show the complementarity of the Page Rank and Electric Betweenness methods at different stages of failure.
As the energy scarcity and environment problems become more and more severe, promoting renewable energy has become an important task and thus energy storage draws increasing attention for integrating renewable energy....
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ISBN:
(纸本)9781839533907
As the energy scarcity and environment problems become more and more severe, promoting renewable energy has become an important task and thus energy storage draws increasing attention for integrating renewable energy. Among many available options, advanced adiabatic compressed air energy storage (AA-CAES) are considered mature and affordable options for gridscale applications. However, the relatively high capital cost hinders the development of AA-CAES system. As a result, the cost-benefit analysis of AA-CAES application is studied in this paper. The thermodynamic characteristics of AA-CAES system are carefully studied and modeled. An optimal configuration method of AA-CAES capacity considering energy arbitrage is proposed and the optimal capacity of each component of AA-CAES is demonstrated. simulation results indicate that the application of AA-CAES in arbitrage market is profitable but the payback period is long. The profit estimations are more realistic compare to conventional battery model. Profitable cost range of AA-CAES is found through sensibility analysis. Augmenting electricity price to improve economic of AA-CAES is discussed at the end.
Degradation state assessment of bearing is an important part of prognostic and health management (PHM) in rotating machinery. Generally, the energy distribution of frequency band is sensitive to degradation state for ...
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The health of rolling bearing plays an important part in the operation of rotating machinery like gas turbine engine. Health monitoring and fault diagnosis of rolling bearings based on vibration signals have been thro...
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The health of rolling bearing plays an important part in the operation of rotating machinery like gas turbine engine. Health monitoring and fault diagnosis of rolling bearings based on vibration signals have been through great development these years. But when sensors are set on the casing instead of the bearing pedestal, and the surrounding structure is very complex, the diagnosis problem becomes much more complicated, which brings more challenges to the signal processing. In this paper, a set of signal processing methods are used to enhance and extract the impact features from casing vibration signals, and to realize the detection of rolling bearing faults. Aself-adaptive decomposition method called intrinsic time-scale decomposition (ITD) is applied to decompose the vibration signal into a series of proper rotation components and a monotonic trend, helping to extract dynamic features of the signal. Teager-Kaiser energy operator is a simple algorithm calculating the energy of a signal and is very sensitive to transient impact faults. As the fault feature transmitted to the casing is relatively week, autoregressive model (AR) and minimum entropy deconvolution (MED) are to enhance the non-stationary impact components. Experiments are taken on the rotor-bearing-casing test rig with minor defects in themain shaft bearing. Testing on the casing vibration signal, this fault feature enhancing and extracting method shows its remarkable ability in rolling bearing fault diagnosis.
power-to-Gas(P2G)plays an important role in enhancing large-scale renewable energy integration in power *** an emerging inter-disciplinary subject,P2G technology requires knowledge in electrochemistry,electrical engin...
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power-to-Gas(P2G)plays an important role in enhancing large-scale renewable energy integration in power *** an emerging inter-disciplinary subject,P2G technology requires knowledge in electrochemistry,electrical engineering,thermodynamic engineering,chemical engineering and system *** at P2G modeling and operational problems concerning the research field of powersystems and the energy internet,this paper briefly reviews the main technologies and application potentials of the P2G system,and makes systematic summaries of major progresses related to P2G’s integration into the power grid in a bottom-top manner,including the modeling of high/room-temperature electrolysis cells,steady-state/dynamic optimization control of the P2G system,P2G’s integrated model and operational strategies at the grid *** the final part of this paper,suggestions are put forward on future research directions of P2G systems from the aspects of modeling and operational optimization.
Due to the economic situation changes and the continuous expansion of new energy power in China, a new evaluation methodology based on multi-criteria decision making (MCDM) should be proposed to promote the comprehens...
Due to the economic situation changes and the continuous expansion of new energy power in China, a new evaluation methodology based on multi-criteria decision making (MCDM) should be proposed to promote the comprehensive development of the new regional power grid. Some criteria were selected to constitute an indicator system from the perspectives of the safety reliability, network structure and economic benefit. Then, an integrated evaluation model was proposed based on fuzzy AHP method and VIKOR method was applied to calculate a series of comprehensive evaluation indexes. A regional power grid was chosen as an empirical analysis to demonstrate the feasibility of the evaluation system.
Aiming at the special working environment of composite insulators at high altitude area,we investigate the creepage discharge characteristics of aged HTV(High Temperature Vulcanized,HTV)silicone rubber materials by UV...
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Aiming at the special working environment of composite insulators at high altitude area,we investigate the creepage discharge characteristics of aged HTV(High Temperature Vulcanized,HTV)silicone rubber materials by UV(ultraviolet radiation,UV)aging method in this *** results show that the creepage discharge flashover voltage first increased,then decreased as aging time increasing,whereas the creepage discharge initial voltage was not significantly affected by aging *** aging time has little effect on creepage discharge *** aging time contributed to shorter endurance time and higher creepage discharge development *** magnitude of discharges increase rapidly in a short time after *** partial discharge detection system was used to detect the whole creepage discharge development *** to the partial discharge characteristics parameters of creepage discharge,we divided the development process of creepage discharge into initial stage,developmental stage,accelerating stage,and critical breakdown *** with characteristic parameters of unaged HTV silicone rubber,the characteristic parameters for the aged HTV silicone rubber exhibited less fluctuation and clear *** aging not only has an effect on the physicochemical and hydrophobic properties of the materials,but also accelerates the development process of creepage discharge under AC *** should be given enough attention in engineering practice,especially at high altitude area.
The characteristics of oil-impregnated pressboard(OIP)insulation in converter transformer are different with that in traditional AC transformers due to the complication of voltage applied on valve side windings of con...
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The characteristics of oil-impregnated pressboard(OIP)insulation in converter transformer are different with that in traditional AC transformers due to the complication of voltage applied on valve side windings of converter *** is a serious lack of empirical research on effect of temperature on creepage discharge characteristics in OIP under combined AC-DC ***,this study investigates the characteristics spectrum of creepage discharge in OIP under combined AC-DC voltage,and explores the effect of temperature on creepage discharge characteristics under different temperature from 70 to 110℃.The experimental results show that the partial discharge inception voltage and flashover voltage decrease as temperature *** times of low amplitude discharge(LAD)decrease and amplitude of LAD *** temperature had an accelerating effect on the development of creepage discharge in the OIP under combined AC-DC voltage Meanwhile,the times of high amplitude discharge(HAD)gradually increase at each stage of creepage discharge with higher *** analysis indicates that the charge carriers easily accumulate and quickly migrate directional movement along the electric field ahead of *** residual charge carriers are more easily dissipated after ***'hump'region of LAD moves to the direction of higher discharge *** interval time between two consecutive discharges drastically *** HAD intensively appear,result in accelerating the development of creepage discharge in OIP insulation.
District multi-energy systems are constructed to reduce environmental impact of energy consumption. This paper introduces a three-layer structure for district energy systems. And two representative operation strategie...
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District multi-energy systems are constructed to reduce environmental impact of energy consumption. This paper introduces a three-layer structure for district energy systems. And two representative operation strategies are proposed focusing on the energy services of the system. The operation strategies are applied to a district which consists of electricity distribution network, natural gas pipe network and heat pipe network. The energy efficiency and CO 2 emission are calculated under different scenarios. The results show that the system operation strategy has a significant impact on the environmental indices. It is suggested to choose the scheme with a priority of electric requirement for the investigated system.
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