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Zheng X.,Xi'an 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.

Xiao J.,Guangzhou Power Supply Bureau | Wen F.,Zhejiang University
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2010

Bilateral contract is one of the major trading schemes in electricity markets, and certainly could also be employed in generation-rights trading. Up to now, the centrally matchmaking trading mode has dominated the generation-rights trading in practice, but bilateral contract is surely another feasible mechanism for consideration. Based on the successful experience in electricity market practices, it is believed that the combination of the centrally matchmaking trading mode and bilateral contract mode, i.e. creating a hybrid market, could lead to a better market operation for generation-rights trading. However, the employment of a hybrid market for generation-rights trading could result in some new problems for system dispatch. In case of congestion, how to curtail equally and reasonably between these two kinds of trading is especially an important issue to be investigated. Given this background, efforts have been made to develop coordinated congestion dispatching models in a hybrid generation-rights trading market. With the enforcement of a coordinated constraint, the two kinds of trading could be treated in a non-discriminatory way. The feature of the developed models is demonstrated with case studies of the IEEE one-area RTS 96-bus system. ©2010 State Grid Electric Power Research Institute Press.

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.

Xiao T.,Guangzhou Power Supply Bureau
Gaoya Dianqi/High Voltage Apparatus | Year: 2015

Partial discharge (PD) of transformer bushings causes degradation of the insulation, resulting in fire and explosion of the bushing. The conventional PD measurement method needs to use the grounding lines of bushing's end screen, making the operation complex, and the measurement is interfered by the pulse signal from grounding network. In order to solve this problem, this study proposed a partial discharge detection and pattern recognition method for the bushing based on ultra-high frequency technology. According to the typical defects in real bushings, four PD defect models were designed on a 110 kV transformer bushing. Then the PD signals of the four defect models were detected by the conventional pulse current method and the proposed UHF detection method, respectively. The results show that: l) the PRPD spectrums of the PD defects obtained by the UHF detection method and the pulse current method are basically identical; and 2) the PD defect types and possible discharge position can be identified according to the morphological features of the PRPD and NV spectrums. This research may promote on-line PD detection of bushings. ©, 2015, Xi'an High Voltage Apparatus Research Institute. All right reserved.

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.

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.

Xiong J.,Guangzhou Power Supply Bureau
Gaoya Dianqi/High Voltage Apparatus | Year: 2016

Studying the distribution characteristics of dielectric loss and capacity incremental values for transformer oil bushings are conducive to grasp the insulation health level of running high voltage bushings. In this paper, basing on a large number of data samples of Guangzhou area, the normal distribution curves of the tanδ and capacitance variation for running high voltage bushings were obtained by comprehensively using histogram and non-parametric inspecting methods under the multiple dimensions of different rated voltage levels. The test results show that the mean and standard deviation of normal distribution curve are larger for products with early technological level and longer running time, the differences of normal distribution curves of the tanδ and capacitance variation are more obvious when the environment humidity is higher than 80%; the differences of normal distribution curves of the tanδ and capacitance variation under different environmental temperature are relatively small. It is presented that the regulations of the allowable values of tanδ and capacitance variation for running high voltage bushings should consider manufacturing technology level and the regional difference. Suggestions can be put forward that the allowable value of tanδ for running high voltage bushings with 110, 220, 500 kV are 0.8%, 0.7%, 0.6% respectively. Measures should be taken such as shortening the test cycle or using high voltage dielectric loss test to track when it is more than 0.5%; the allowable value of capacitance variation is ±3%, reasons should be find out when it is over ±2%. © 2016, Xi'an High Voltage Apparatus Research Institute Co., Ltd. All right reserved.

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.

Yao Y.,Guangzhou Power Supply Bureau | Cai Y.-C.,Guangzhou Power Supply Bureau
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2010

By integrating a discrete particle swarm algorithm (DPSO)with an interior point method(IPM), a hybrid strategy for the optimal reactive power flow (ORPF) problem is proposed. First, the original ORPF problem is converted to a continuous non-linear programming problem by relaxing the discrete variables, and the initial solution is obtained by the IPM. Then according to the discrete feature of the control variables, the original ORPF problem is decomposed into a continuous optimization sub-problem and a discrete optimization sub-problem, which are solved by IPM and DPSO respectively. By solving the two sub-problems alternately, the optimal solution of the ORPF problem can be obtained. IPM and GA take advantage of each other, so that the efficiency of the hybrid strategy is greatly improved. Furthermore, the numerical example of IEEE 30-bus and IEEE 118-bus system is employed to validate correctness and effectiveness of the proposed algorithm, and the result based on this algorithm is compared with that based on conventional discrimination algorithm.

Zheng C.,Guangzhou Power Supply Bureau | Guan L.,South China University of Technology
Dianwang Jishu/Power System Technology | Year: 2012

It is an important approach to plan and construct ultra high voltage direct current (UHVDC) transmission projects to cope with regional difference between energy source and distribution of productivity. To analyze the influences of UHVDC transmission on power systems, fault trees due to failure characteristics of UHVDC transmission system are established on the basis of analyzing control protection functions; the operational reliability of UHVDC transmission system is assessed by fault tree analysis and time-frequency method based on subsystem division. After that, the principle of simulation and the foundation of analysis are established. Then the influences of severe UHVDC faults are simulated by PSD-BPA in the year 2012. Dynamic recovery performance of the receiving power grid after severe fault is assessed by indices, which also considers variable proportion of induction motors in load model. Research results show that UHVDC transmission system possesses high operational reliability; nevertheless severe faults will lead to instability in UHVAC systems. Thus in the operation and drafting of scheduling of dispatching, appropriate control strategies should be set and the influences of load model on recovery performance should be taken into account.

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