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Liao R.,Chongqing University | Wang K.,Chongqing University | Yin J.,Xiangtan Power Supply Bureau | Yang L.,Chongqing University | And 2 more authors.
Gaodianya Jishu/High Voltage Engineering | Year: 2012

The mineral oil-paper samples with different initial moisture contents (1%, 3%, and 5%) were thermally aged under 90°C in order to study the influence of the mechanism of initial moisture on thermal degradation process of oil-paper insulation. All the samples were periodically sampled and the degree of polymerization (DP) of insulation paper, the moisture content of oil-paper samples, furfural, acid in oil, and so on were measured during the aging process. Moreover, by using a material simulation software, oil molecule with different moisture contents, furfural molecules and hydroniumions were modeled, respectively. Then, diffusion coefficients, interaction energies, and radial distribution function among furfural molecule, hydroniumion and oil molecules with different moisture contents were calculated based on dynamic molecular simulation technology. The obtained results show that moisture in both oil and paper is fluctuant during the aging process. Additionally, furfural and acid in oil, which do not correspond with the decrease of DP, are markedly influenced by the moisture of oil-paper system. Molecular simulation results reveal that the increased moisture can not only reduce the diffusion capability of furfural and hydroniumions, but also result in more stable hydrogen bonds between moisture and furfural & hydroniumion. Meanwhile, the interaction energies between moisture and furfural & hydroniumion have been changed due to the mutual polar effect of moisture and furfural & hydroniumion. The experimental results and molecular simulation results agree with each other, and the relevant results can provide theoretical reference for in-depth study on the aging mechanism and diagnosis of oil-paper insulation.


Zhang X.,Jilin Railway Vocational and Technical College | Su H.,Xiangtan Power Supply Bureau
Gaoya Dianqi/High Voltage Apparatus | Year: 2016

Considering the fact that there are many qualitative indexes in performance analysis and evaluation of a grid-connected wind power generation system and each index is random and fuzzy, a performance analysis model of grid-connected wind turbine generator system is established based on membership cloud gravity center. The comprehensive evaluation index system of performance analysis for a grid-connected wind power generation system is analyzed and constructed with respect to four aspects, i.e. technical parameters, overall function, system reliability, and maintainability. Then, the values of the evaluation indexes are transformed to cloud model, and the weight of each index is determined. Finally, the modified weighted deviation degree is calculated and put into the qualitative judgment cloud generator to obtain performance evaluation result of the wind power generation system. The proposed method is employed to analyzed the performance conditions of a certain wind power generation unit, and is compared with the conventional fuzzy comprehensive evaluation method to verify the superiority and effectiveness of the proposed model. © 2016, Xi'an High Voltage Apparatus Research Institute Co., Ltd. All right reserved.


Wang Z.-Y.,Nanchang Institute of Technology | Su H.-Y.,Xiangtan Power Supply Bureau
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2014

To improve the power supply reliability of distribution system is an important goal of smart grid construction. Due to various influencing factors, it is of great risk for the power supply enterprise to invest in improving the distribution network power supply reliability. By elaborating the basic principles and structure characteristics of the power distribution automatic system, a new cost-benefit analysis model for reliability of distribution network automation is presented. Combined with the engineering calculation method for distribution system reliability, the quantitative calculation of the costs and benefits of improving distribution system reliability is conducted, the economic evaluation of the modification scheme for distribution automation system is made based on normal cloud theory, and multiple comprehensive evaluation indexes are defined, which provides intelligent decision support for power management layer. An actual distribution system example analysis shows that the model has better practicability and operation.


Xu H.-J.,Nanchang Institute of Technology | Wang Z.-Y.,Nanchang Institute of Technology | Su H.-Y.,Xiangtan Power Supply Bureau
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2013

In order to solve the problem of randomness and fuzziness in power transformer fault diagnosis, a new fault diagnosis method for power transformer based on feedback cloud entropy model is proposed. After the statistic analysis of the collected fault examples of chromatographic data for transformer oil, which is put into Bayesian feedback backward cloud generator as cloud drop, the transformer fault diagnosis standard normal cloud model is built based on parameter values of fault characteristic gases cloud model. The model integrates cloud correlation coefficient and information entropy theory, reduces the dependence on the single standard normal cloud model and digs more information of the dissolved gases in transformer oil, and improves the accuracy of transformer fault diagnosis. By increasing training samples and correction cloud model parameter, the effectiveness of the model can be further enhanced. The results of example show that the model has higher accuracy, and has well theoretical value and application prospects.


Su H.,Xiangtan Power Supply Bureau | Li R.,Guangxi University
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2012

In order to solve the problem that the multi-objective transmission network planning under smart grid condition, under smart grid infrastructure, the investment cost of the planning schemes was applied to weight economic performance, the outage loss of customers was applied to measure the reliability of the schemes, available transfer capability of the network was applied to evaluate the flexibility of the schemes, the method of using the system expansion factor was applied to quantify the adaptability of the schemes, and the lowest limit value of the line betweenness was applied to assess the invulnerability of the scheme. On this basis, a multi-objective transmission network planning model based on cosine prioritizing theory was established. The entropy theory was introduced to determine the weight coefficients of indices and the value of weight could avoid to be judged by subjectivity. In the high-dimensional space, by comparing the cosine value between directed line segment in each scheme and ideal directed line segment in ideal scheme, the optimum scheme was obtained, so that it gives effective guidance for the future smart grid planning and construction. Analysis of an example verified the validity and feasibility of the method. © 2012 Chin. Soc. for Elec. Eng.


Xia F.,Nanchang Institute of Technology | Fan L.,Nanchang Institute of Technology | Su H.-Y.,Xiangtan Power Supply Bureau
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2012

According to the characteristics of the medium and long term load forecasting, a heuristic radial basic function (RBF) neural network load forecasting model is proposed based on multiple targets such as the load gross quantity in this year, the load growth quantity in this year, the load gross quantity in prior year, the load growth quantity in prior year, and the gross domestic product (GDP). Firstly, we use the orthogonal signal correction to process primary data, and use the partial least square method to fit the unit of GDP electricity consumption. Then taking unit of GDP electricity consumption as heuristic operator, we assume the load gross quantity of next year reasonably based on original load data, and use the heuristic operator to get the corresponding GDP. Combining with the other indexes, we construct neural network extended training samples, and transform the neural network extrapolation forecast into the interpolation evaluation creatively. Finally, the predicted value of heuristic neural network forecasting model is corrected on the basis of rough set theory to further improve the forecasted result. The results of practical examples show that the proposed method has higher forecast precision and the model has feasibility and validity.


Wang Z.-Y.,Nanchang Institute of Technology | Fan L.,Nanchang Institute of Technology | Su H.-Y.,Xiangtan Power Supply Bureau
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2012

According to the interval number concept of assessment standard of power quality, a new synthetic power quality evaluation model based on interval number theory is proposed. Based on the original indexes weight range, the subjective weighting is obtained using the linear goal programming model, and the objective weighting is obtained using the improved scatter degree, then the comprehensive weighting could be determined based on addition principle. On this basis, a multiple objective decision-making ideal interval method is introduced to calculate the distance between indexes data of the sample and ideal interval. The approach degree between the sample data and power quality standard mode is defined by using the normalized reciprocal of the distance, thus the comprehensive evaluation of power quality is achieved. This method not only can perform comprehensive assessment, but also can evaluate power quality difference more precisely within the same power quality grade. The feasibility and validity of the proposed model are demonstrated with the results of the practical example.


Fan L.,Nanchang Institute of Technology | Xia F.,Nanchang Institute of Technology | Su H.-Y.,Xiangtan Power Supply Bureau | Li R.-Q.,Guangxi University
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2012

According to the characteristics of only considering the fuzziness and ignoring the randomness of evaluation indices for insulator contamination condition fuzzy synthetic evaluation model, a new insulator contamination condition synthetic evaluation model is proposed based on cloud theory. The number of discharge pulse, operation periods, weather conditions, the temperature and the relative humidity are chosen as five characteristic parameters affecting insulator condition, and the evaluation indices system is established. The cloud membership function which is composed of the expected value, the entropy, and the hyper entropy is used to describe the fuzziness and the randomness of the grade limit value for insulator condition synthetic evaluation, which softens the grading range. Clustering analytic hierarchy process is used to obtain subjective weighting, the variable weighting is determined by modifying the subjective weighting based on balancing the evaluation indices. On this basis, the coefficient of credible degree is defined, and the model not only obtains the result of synthetic evaluation but also provides the credibility information of the evaluation result. The practicality and effectiveness of the model is demonstrated by the results of actual numerical example.


Xia F.,Nanchang Institute of Technology | Fan L.,Nanchang Institute of Technology | Su H.-Y.,Xiangtan Power Supply Bureau | Li R.-Q.,Guangxi University
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2012

Aiming at the characteristics of the integration evaluation of power quality, the weights of indexes in power quality synthetic evaluation are obtained by integrating the analytic hierarchy process method, the entropy method and the mean square difference method. Given a full consideration to the fuzziness and randomness of the boundary value of power quality classification levels, combining the characteristic of uncertain reasoning of the cloud model and the advantage of qualitative and quantitative analysis of the matter element analysis theory, a comprehensive power quality evaluation model is proposed based on cloud matter element analysis theory. By establishing the standard cloud matter element model of power quality comprehensive evaluation and calculating the association degree between the matter element to be evaluated and standard cloud matter element model, the coefficient of credible degree is defined, which allows the model not only obtains the level of power quality but also provides the credibility information of the evaluation result. The superiority and effectiveness of the model is demonstrated by results of actual numerical example.


Chen J.-Y.,Guangxi Power Grid Corporation | Cai H.-M.,Guangxi Electrical Power Institute of Vocational Training | Su H.-Y.,Xiangtan Power Supply Bureau
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2012

Aiming at many kinds of uncertain information in the power generation system reliability evaluation under the electric power market condition, a power generation system reliability flexible evaluation model which contains evaluation theory, evaluation index, and evaluation method is proposed based on blind number theory. This model uses the blind number to express node information, which effectively deals with the impact of primitive parameter uncertainty on the reliability evaluation. The reliability index's sensitivity formula is used to effectively find the weak link restricting system reliability, and then the reliability cost-benefit assessment for the power generation system is carried out. The numerical example of IEEE-24 buses reliability test system demonstrates the correctness and availability of the proposed approach.

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