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Yang J.,North China Grid Company | Sheng H.-H.,Beijing Electrical Power Corporation | Wei X.-W.,Beijing Extra High Voltage
Gaoya Dianqi/High Voltage Apparatus | Year: 2010

An accident of 500 kV transformer inner short circuit is explored by the change analysis of the oil chromatogram after accident, the local discharge online monitoring, and ultimate degradation analysis. It is found that this accident is caused by inner short circuit of high voltage winding. The insulation effect analysis of the phenomenon of Cu 2S in the accident is performed. The accident analysis also includes soldering quality, insulation quality, and working environment, etc. Preventing measure is hence suggested.

Shen H.,China Electric Power Research Institute | Chen W.,State Grid Corporation of China | Wang S.,Beijing Electrical Power Corporation | He Z.,China Electric Power Research Institute | Chen Y.,Beijing Electrical Power Research Institute
Dianwang Jishu/Power System Technology | Year: 2011

In recent years the lightning stroke-caused wire-breakage faults occasionally happen in overhead distribution lines in China and these faults seriously jeopardize the secure operation of power grid, so it is the key for the solution of this problem to make the mechanism leading to lightning stroke-caused wire-breakage clear. Existing research results pay attentions on qualitative theoretical analysis and the experimental verification is in absence. Two processes, i.e., the line to earth discharge as well as arcing and combustion caused by power frequency sustaining current of lightning-stroke overhead line, are simulated in laboratory, and the conductor burning in 10 kV distribution system caused by arc due to power frequency sustaining current under the condition of typical short-circuit fault is mainly researched. Research results reveals that whether the root of arc caused by power frequency sustaining current can freely move or not is the basic reason of the phenomena that the arc-resistant performance of bare conductor is strong and the arc-resistant performance of insulated conductor is weak. Experimental results validate the fact that after the arcing due to power frequency sustaining current the breakage of the insulated conductor is inevitable and yet the breakage probability of bare conductor under the same condition is very low. The obtained conclusion is available for the prevention of wire-breakage of overhead transmission line due to lightning stroke, namely it is necessary to adopt the measure to prevent wire-breakage of lightningstroke insulated overhead transmission lines and it is not necessary to adopt such a measure for overhead transmission line using bare conductors.

Yao G.,Wuhan University | Wen X.-S.,Wuhan University | Lan L.,Wuhan University | Han W.,Beijing Electrical Power Corporation | Liu H.,Wuhan University
Gaodianya Jishu/High Voltage Engineering | Year: 2011

Characteristics of pollution Flashover and raining flashover of DC equipment are restricted by their surface RTV coating insulation characteristics. In order to research the influence of oil leakage of transformer bushing on RTV insulation characteristics, ordinary RTV and insulation nanocomposite modified by nano-SiO2 and fluoride polysiloxane were selected, and the microstructure and mechanical properties of RTV materials were comparatively investigated by using SEM, EDS and universal testing machine. By the national standard GB 1739-1989, oil accelerated aging immersion tests were investigated, hydrophobic recovery characteristics of RTV in different immersion oil time and recovery time were studied, and the influences of environmental factors and component of pollution on hydrophobicity of RTV at pre-and post-oil impregnation were analyzed. The results indicate that the hydrophobicity and hydrophobic recovery characteristics of RTV are decreased by high-temperature transformer oil, and comprehensively modified RTV nano-composite materials show better characteristics than common RTV on mechanical properties and oil resistance. According to the hydrophobicity, the recovery speed and degree of RTV closely depend on the immersion oil duration, and regularly vary during a given immersion oil period. Pollution composition, ambient temperature and relative humidity have obvious effects on hydrophobic recovery characteristics of RTV.

Xiao Y.,Beijing Jiaotong University | Kang N.,Beijing Jiaotong University | Chen X.,Beijing Electrical Power Corporation
Journal of Information and Computational Science | Year: 2015

Considering the fact that membership functions and factor weights are highly depend on man in fuzzy synthetic evaluation, a model for power transformer condition assessment based on Support Vector Machine (SVM) is presented. In order to eliminate the false feature and retain the true, the information data of the transformer is preprocessing with Kernel Principal Component Analysis (KPCA) first, the results become the inputs of SVM to form the KPCA+SVM model for transformer evaluation. To enhance the effect of evaluation, an improved KPCA+SVM model is proposed. Mixtures of kernels and parallel optimized strategies are used. The example shows the effectiveness and superiority of the improved model. 1548-7741/Copyright © 2015 Binary Information Press

Liu Y.-G.,Chongqing University | Meng X.,Chongqing Electric Power Research Institute | Tian J.-H.,Chongqing University | Wang S.,Beijing Electrical Power Corporation
Chongqing Daxue Xuebao/Journal of Chongqing University | Year: 2010

The number of underdetermined equation, which is limited by the grounding down lines, reduces the grounding grid corrosion diagnostic precision. Based on the grounding grid fault diagnosis method and sensitivity analysis, the value of slip resistance change on the impact of the port resistance in several cases, such as small span, large span and edge, center and symmetrical cross-line of the grounding grid, is analyzed. A new method which is used to select the node pairs to calculate the corrosion situation of grounding grid is presented. Based on this method, the simulation analysis and field test has been done. The experimental results show that this method could improve the accuracy and efficiency of grounding grid fault diagnosis.

Zhang C.-X.,North China Electrical Power University | Sun W.-Z.,North China Electrical Power University | Tu Y.-P.,North China Electrical Power University | Lu Y.-H.,Beijing Electrical Power Corporation
Gaodianya Jishu/High Voltage Engineering | Year: 2011

Taking the cable sheath overvoltage caused by an arc discharge fault in the operation of single-phase gas insulated switchgear (GIS) disconnector as an example, we numerically simulated the cable sheath overvoltage under different cases. Simulation results show that, the higher the breakdown voltage of air gap is, and the shorter the arc cut-off time is, the more serious the cable sheath overvoltage would be. Adding the sheath protector is the most effective way to restrain the overvoltage of the cable, however, the thermal capacity of the sheath protectors in the case of the arc reignition in GIS disconnector should be considered. If the graphite electrode outside the crossing connection of the cable discharges, the sheath voltage at the discharging point will decrease greatly, but the energy distribution of sheath protectors will change. It is found that arc reignition in GIS disconnector will cause the damage of sheath protector, resulting in graphite electrode discharging, and then more sheath protectors are destroyed further. The simulation results have reference values for the cable sheath overvoltage protection.

Li Y.,Beijing University of Civil Engineering and Architecture | Ru L.,Beijing University of Civil Engineering and Architecture | Niu J.,Beijing Electrical Power Corporation
Proceedings of the 2011 6th IEEE Conference on Industrial Electronics and Applications, ICIEA 2011 | Year: 2011

Power structure optimization is to determine the planning time, the type and the capacity of power supply, thus the best way to meet the load demand for development. With the help of Markov decision-making process (MDP), it has been established based on the grid-connected PV system generation. Using the optimal strategy of MDP, one step transition probability matrix and the expected total reward criterion have been obtained. According to weather conditions, PV generation was distributed to load, grid power and batteries. The example result shows that the expected total reward criterion of MDP applying to grid-connected photovoltaic system is more powerful. © 2011 IEEE.

Zhang L.,Huazhong University of Science and Technology | Lou S.,Huazhong University of Science and Technology | Chen Y.,Beijing Electrical Power Corporation | Wu Y.,Huazhong University of Science and Technology | Huang X.,Huazhong University of Science and Technology
Dianwang Jishu/Power System Technology | Year: 2016

After analyzing operation characteristics of battery swapping station (BSS) for electric vehicles (EVs), a battery state transition model in BSS is proposed. EV swapping demand model is presented based on EV daily consumption profile. The scenario reduction algorithm based on Kantorovich distance is used to reduce EV swapping demand scenarios. On this basis, a battery capacity optimization model in BSS under time-of-use pricing, taking the relevant constraints of charging/discharging ability and EV swapping demand into account, is developed to minimize the investment cost, maintenance cost and charging/discharging cost of batteries. A case study of certain BSS is carried out, and influences of battery price and electricity price difference between peak and valley on optimization results are analyzed. Results show that battery capacity configuration will increase with battery price decrease and electricity price difference increase between peak and valley. © 2016, Power System Technology Press. All right reserved.

Huang R.,Beijing Electrical Power Corporation | Pu T.,China Electric Power Research Institute | Liu K.,China Electric Power Research Institute | Yang Z.,China Electric Power Research Institute | Chen N.,China Electric Power Research Institute
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2015

Relying on Beijing Yanqing smart grid innovation demonstration projects, an analysis is made on the new energy basic conditions and characteristics of Yanqing District. The construction of the demonstration area is elaborated at length with respect to items from the form of energy supply/consumption, the main carrier undertaking energy delivery, and decision-making management to public service. An application framework model of the energy internet is developed, and the wide-area tide flow supporting AC/DC active power distribution network is described in detail as is the hierarchical partitioning of distributed intelligent control management and open public service mode. The methods and channels of exploring future management and business modes are recommended. © 2015 State Grid Electric Power Research Institute Press.

Li T.,Beijing Electrical Power Corporation
Dianli Zidonghua Shebei/Electric Power Automation Equipment | Year: 2010

The one-and-half breaker scheme is applied to 500kV bus of Three Gorges right bank hydropower station and its main bus is equipped with the segment switch. The on-off state of the segment switch is taken as the state of its position contact or hard strap, but these auxiliary binary variables cannot truly reflect its actual state, which may lead to bus protection malfunction, especially when there is signal error or misoperation. The problems existed in current configuration scheme are analyzed and the solution is proposed: as the segment switch is equipped with CTs at both sides and several differential protections with different selection ranges are configured in bus protection, the method of digital logic circuit analysis is used to obtain the operational mode of segment switch by analyzing the logic combination of differential operating data, which can truly reflects its actual state.

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