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Yu Z.Q.,Yangtze River Scientific Research Institute | Wang X.,Shenzhen Power Grid
Advanced Materials Research | Year: 2014

The test data of circuit-breaker operating characteristics is important parameter to monitor the circuit- breaker. The unexpected opening of ABB HPL Series circuit-breaker under 30% control voltage in the recent operating characteristics in Shenzhen is analysed in this paper.The root cause of failure is identified. Two solutions are proposed: adjust the gap between coil and armature and replace the trip coil "open", to eliminate such failures, ensure the safe and reliable operation of the circuit breaker. © (2014) Trans Tech Publications, Switzerland. Source


Xiong P.,Zhejiang University | Sun D.,Zhejiang University | Deng L.,Shenzhen Power Grid
Dianwang Jishu/Power System Technology | Year: 2016

Aiming at operation of grid-connected voltage-sourced converters (VSC) under universal and dynamically varied harmonic voltage conditions existing in real power grid, this paper proposes an improved sliding-mode-based direct power control (SMC-DPC) strategy under universal harmonic grid voltage. Due to tasks to all harmonics, its implementation has no need of accurate detection of concrete order and phase position of harmonics, thus with certain engineering application potentials. Based on past researches, integral mathematic model of VSC under universal harmonic circumstances is founded, three different control objectives, i.e. sinusoidal current output, active and reactive power fluctuation eliminations, are devised and final improved SMC-DPC strategy under universal harmonic grid voltage is performed. Simulation results reveal that the improved strategy enhances VSC operating performance under universal grid harmonic voltage, contrasting to traditional SMC-DPC. © 2016, Power System Technology Press. All right reserved. Source


Chen W.,Chongqing University | Du J.,Chongqing University | Ling Y.,Shenzhen Power Grid | Xie B.,Chongqing University | Long Z.,Chongqing University
Yi Qi Yi Biao Xue Bao/Chinese Journal of Scientific Instrument | Year: 2013

Based on the air-gap discharge model in oil-paper insulation, the experiments on the developing characteristics of partial discharge were performed using constant voltage method in laboratory. In this paper, the variation of discharge energy in discharge development process is studied. At the same time, the discharge repetition ratio n is introduced, and the average discharge energy per second Wasec is proposed as a new feature quantity. The analysis shows that Wasec can be used to describe the development characteristics of partial discharge very well. On the basis of constructing the PRPD spectrum, the line frequency phase(φ)occurred in discharge is introduced, and a three-dimensional statistical spectrum, φ-w-n based on discharge energy is constructed. The partial discharge two-dimensional gray scale images based on discharge energy and phase, w-φ are obtained. As traditional moment parameter has its shortages, the wavelet theory was introduced into the moment characteristic parameter extracting process of partial discharge gray scale images; 62 group sample points for start discharge, developing and breakdown, and the wavelet moment features for different scale parameters and translation parameters were obtained from the gray scale images. According to the wavelet moment features extracted at different discharge times, under the condition of no prior knowledge, the fuzzy C-means clustering method is used to divide the whole air-gap discharge process into four stages, namely, the start discharge and shock developing stage, the weak discharge stage, the outbreak discharge stage and the discharge pre-breakdown stage. Source


Yuanyuan W.,Xian Jiaotong University | Shengchang J.,Xian Jiaotong University | Jinyu L.,Xian Jiaotong University | Lipeng Z.,Xian Jiaotong University | And 2 more authors.
IEEE Transactions on Plasma Science | Year: 2014

Detection of ultraviolet images is proved to be both effective and convenient in discharge monitoring nowadays. In a self-designed gas chamber with observation windows installed, characteristics of 50-Hz ac discharges in SF6 atmosphere were observed in the needle-to-plane model and the floating potential model. Ultraviolet images of the discharges in different periods of the voltage process are presented, and correspondence is found with the variation of the discharge capacity. © 2014 IEEE. Source


Wang Y.,Xian Jiaotong University | Ji S.,Xian Jiaotong University | Zhang Q.,Xian Jiaotong University | Ren J.,Xian Jiaotong University | And 2 more authors.
IEEE Transactions on Plasma Science | Year: 2014

The detection of gas decomposition products is widely used to diagnose the inner condition of SF6-insulated electrical equipment for its anti-interference ability and high sensitivity. A discharge chamber with Teflon coating inside was designed, with adjustable defect parameters and the volume nearly the same as real ones in gas-insulated switchgear. With the assistance of newly developed dual gas chromatography detection system, this paper investigated the influences of relatively low moisture on the discharge characteristics and gas decomposition under corona and mild spark in SF 6. Considering notable hydrolysis reactions in the main gas volume and on the vessel walls, SO2F2, SO2, and S 2OF10 were selected as typical gas decomposition products. The average discharge capacity and its fluctuation were found to decrease with the increase of moisture content within research scope, which is related to the electronegativity of water molecule. The concentration of typical decomposition products under various moisture conditions was observed in detail. The results show that in mild spark, O atom in S2OF10 mainly originated from oxygen rather than water vapor in SF6. To diagnose internal insulation condition by only monitoring, the magnitude of discharge capacity is proved unreliable. A new parameter, the concentration ratio of SO2/S2OF10, was proposed to group moisture content and discharge types. © 2014 IEEE. Source

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