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Zheng X.,Xian Jiaotong University | Wang J.,Shaanxi Electrical Power Corporation Planning and Evaluation Center | Li Y.,Guangzhou Power Supply Bureau
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2013

Water treeing is the main inducement of insulating breakdown of long-time operation polyethylene (PE) power cables in humid environment. Water tree propagates to some extent may initiate electrical tree, which can eventually lead to insulation breakdown of power cables. The influence of moisture and water tree degradation on the initiation and propagation of electrical trees in cross linked polyethylene (XLPE) was studied. During the experiments, peroxide cross- linked polyethylene was chosen as the experimental material, liquid needle electrode and high frequency accelerated aging method were used for water tree development, and real-time digital microscopic camera system was used for observation of water-tree-transformed electrical treeing. The transformation of electrical trees from wetting and drying water tree samples with different electrodes (water needle electrode, steel needle electrode) was studied at different voltages (15kV, 20kV). Three experimental results are obtained. The average electrical tree initiation time of non-deterioration samples is shortest, that of wetting water tree samples is longest, while that of drying water tree samples is the medium of the two mentioned above. The electrical tree initiation rate of drying water tree samples is highest, that of wetting water tree samples is lowest, and that of non-deterioration samples is the medium of the two mentioned above. When water needle electrode is used in the three kinds of samples, the electrical trees initiated are all branch-like. The different mechanisms of electrical treeing in the three kinds of samples are studied. © 2013 Chin. Soc. for Elec. Eng.

Liu G.,South China University of Technology | Lei C.,South China University of Technology | Liu Y.,Guangzhou Power Supply Bureau
Dianwang Jishu/Power System Technology | Year: 2011

The temperature of power cable conductor of being operated cable is the foundation to judge whether the cable reaches its rated current carrying capacity or not. To analyze the accuracy of cable conductor temperature calculated by simplified thermal circuit model, based on the thermal circuit model to calculate the temperatures of different layers of 110 kV XLPE cable and its simplified model, by means of Matlab software the cable surface temperature-based computation expression to calculate cable conductor temperature is derived, and the error between the cable conductor temperature calculated by complete thermal circuit model and that by its simplified model are computed theoretically, then the functional relation between the error and the current applied to the cable is given. Meanwhile, a transient temperature rise test of directly buried cable is designed. According to the measured data of cable surface temperature, the temperatures of conductors and insulating layers are calculated by the simplified model, then the comparative analysis on the errors between the temperatures of conductors and insulating layers calculated by the simplified model and the measured temperatures of conductors and insulating layers is performed. Analysis results show that the errors between the cable conductor temperatures calculated by simplified model and the measured cable conductor temperatures are inside the allowable range, thus in engineering application the simplified thermal circuit model can be used to calculate cable conductor temperature by surface temperature of the cable.

Chen J.,Guangzhou Power Supply Bureau
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2011

Normally, bus protection is not configured within 10 kV substation system. When bus accident happened, over-current backup protection on transformer's low voltage sides acts to switch off the fault. The act delay may cause partial damage of the primary equipments. The research purpose here is to reduce damage risk of the main transformer and switch box during bus short circuit accident. As a part of 110 kV Dongfang substation automation system modernization project, a generic object oriented substation event (GOOSE) based 10 kV bus protection solution is proposed. Utilizing GOOSE signal transmission among network devices, protection's fast action is fulfilled during accident. The solution has already implemented at Dongfang station from Jan. 28th, 2010, and it operates well so far. © 2011 State Grid Electric Power Research Institute Press.

Chu Q.-X.,South China University of Technology | Ouyang X.,Guangzhou Power Supply Bureau | Wang H.,Huawei | Chen F.-C.,South China University of Technology
IEEE Transactions on Microwave Theory and Techniques | Year: 2013

A method to design TE01δ-mode dielectric-resonator (DR) filters with transmission zeros is proposed. The feeding probes, extended along ring DRs, are used to excite the TE01δ mode and introduce transmission zeros. By rotating the angle of the feeding position, transmission zeros can be shifted to the lower or the upper stopband. Thus, TE1 01δ-mode DR filters with quasi-elliptic responses are realized with only iris coupling components. Based on this method, second-and fourth-order filters with different responses are designed and fabricated. Measured results confirm the predicted performance. © 2012 IEEE.

Li G.,Guangzhou Power Supply Bureau | Zhu G.-L.,South China University of Technology
Gaoya Dianqi/High Voltage Apparatus | Year: 2013

This paper presents a preliminary study of switchgear status detection and evaluation for distribution system, suggests that there are two ways which are sample detection and status monitoring for the switchgear status detection. According to current existing status detection methods, status evaluation can be divided into global evaluation and individual evaluation. Global evaluation is based on the results of the sample detection, and individual evaluation results take the status monitoring results as the primary reference. The status variables of the individual evaluation mainly include fundamental data, operation and patrol, gas pressure, infrared test, and partial discharge test. The application in Guangzhou proves the operability and reliability of this method.

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