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Tian Y.,Huazhong University of Science and Technology | Wu X.-X.,Wuhan University of Technology | Zhang H.,EHV Administration of Hunan Electrical Power Corporation
Gaoya Dianqi/High Voltage Apparatus

In order to improve the simulation precision of VFTO in GIS, this paper presents an overview on arcing models of disconnector (DS), including linear resistor model, time-varying resistor model, segmental model, black box model, spark resistor model and so forth. Modeling techniques of these models were discussed and the limitations of different arc models were also analyzed. Finally the paper indicates that factors such as voltage level, gas medium, structure of DS should be taken into consideration during modeling process, and then the single arcing model should be applied to the multi-reignition process in the basis of the reasonable criteria of breakdown as well. Source

Li Y.-J.,Hunan Institute of Engineering | Huang S.-P.,Hunan Institute of Engineering | Tang J.-D.,EHV Administration of Hunan Electrical Power Corporation
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control

On the condition of getting the parameters of transmission line and electrical quantities of two terminal of transmission line, the common two-terminal fault location algorithms can give an accurate fault location. But in the real application, the values of voltages and currents which are transferred by voltage transformers and current transformers have errors inevitably. Because of this, the accuracy of fault location algorithms may decrease or even a failed fault location turns out. In this paper, by introducing and comparing the principles of four common two-terminal fault location algorithms, the measurement errors of voltage transformers and current transformers are introduced and simplified based on practical engineering. Under the several typical models of measurement errors proposed, the adaptability to measurement errors for all kinds of two-terminal fault location algorithms is compared by simulation. Results of simulation prove that the sequence voltage ratio algorithm of line model based on data correction has the best adaptability. Source

Du L.,Chongqing University | Li X.,Chongqing University | Li X.,Hunan Electrical Power Research Institute | Wang L.-R.,EHV Administration of Hunan Electrical Power Corporation | Sima W.-X.,Chongqing University
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control

This paper proposes an approach of temporary overvoltage layered recognition based on multistage support vector machine in power system. Firstly, on the basis of temporary overvoltage classification, a temporary overvoltage multi-level recognition system is built, and the classifiers are constructed based on binary trees of multistage support vector machine. Then, according to field overvoltage data in a substation, time-domain statistical features and wavelet time-frequency features of three-phase and zero sequence voltage are extracted and selected step by step, and finally these features are used as input vectors of M-SVM to classify temporary overvoltage. The field data indicate that the proposed method has advantages of less training samples, shorter training time and high recognition rate, and can be well applied to power system temporary overvoltage identification. Source

Yan G.,Wuhan University of Technology | Wu X.,Wuhan University of Technology | Tian Y.,Huazhong University of Science and Technology | Zhang H.,EHV Administration of Hunan Electrical Power Corporation
Gaoya Dianqi/High Voltage Apparatus

Almost of the electromagnetic transient phenomena in the power system are caused by arc discharge when operating switchgears. With the development of the transmission voltage level, the transient electromagnetic problems become more serious. This paper summarizes the characteristics and the interference mechanism of the electromagnetic transient phenomena, emphatically analyzes the recent research trends in terms of the mathematical models and field measurement technology. The analysis shows that to establish precise and effective single-discharge arc model and multi-reignition arc model is of great importance to the study of the transient electromagnetic interference by simulation method. Among them, the single-discharge arc model is developing with trends of hybrid arc model based on the physical model and black-box model. To obtain the criterion of arc-reignition is the research emphasis of multi-reignition arc model. For ultra-high voltage (UHV) applications, we should attach great importance to the thermal breakdown which is one of the reasons leading to the arc-reignition. According to the field testing requirements (low-noise, ultra-broad-band, high-dynamic response, high-precision), to develop the sensor measurement system for the transient electric field and magnetic field in UHV substation is the most important to the field testing technology's research. Source

Li Z.-S.,EHV Administration of Hunan Electrical Power Corporation | Li W.-L.,EHV Administration of Hunan Electrical Power Corporation | Yao J.-G.,Hunan University | Yang Y.-J.,State Grid Electric Power Research Institute of China
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering

In view of the close relationship between thermal distribution and conditions about contamination and wetness on insulators' surface, a detection method for on-site pollution level of insulators is proposed based on infrared-thermal-image processing. The procedures of detection were as follows: Firstly, infrared thermal images were denoised with the stationary wavelet-domain local-adaptive method to suppress white-noise interference in infrared imaging. Secondly, Otsu's method was adopted for image segmentation on the basis of logarithmic transformation to the denoised images. Thirdly, edge points of disc surface of insulators were sampled through scattering lines at different angles from the barycentric coordinates, which were computed from binarized images. Fourthly, the elliptic equation for disc surface edge was fitted by the least square method. Fifthly, the ellipse image region above its long axis was abstracted and normalized. Finally, the gray histograms of the normalized images were calculated. According to above procedures, a feature library was established, including massive infrared-thermal-image gray histograms of various pollution-level insulators under different humidity. On-site pollution level was evaluated by maximum comparability criteria of gray synthetically relational degrees with samples under the nearest humidity condition. Experimental results proved the method's feasibility and effectiveness in detection of on-site pollution level for insulators. © 2010 Chin. Soc. for Elec. Eng. Source

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