Yunnan Power Company

Kunming, China

Yunnan Power Company

Kunming, China
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Liu T.,Yunnan Power Company | Liu X.,Chongqing University | Liang S.,Yunnan Electric Power Research Institute | Wang J.,Chongqing University | Yao C.,Chongqing University
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2017

Residual flux may cause strong inrush current on transformers and affect measuring accuracy of current transformer (CT). Nowadays, measurement of residual flux of transformer core, however, is not standardized. Owing to the convenience of residual flux measurement, alternating polarity DC voltage source, which is used for characterizing residual flux and magnetic remanence coefficient of ferromagnetic core, is demonstrated in this paper. By applying alternating polarity DC voltage generated by half-bridge circuit on windings, negative and positive saturation points of ferromagnetic core are reached, respectively. The saturated part of hysteresis loop is obtained via plotting magnetic flux-current curve during the whole process. Residual flux and magnetic remanence coefficient are then calculated based on the obtained hysteresis loop. In addition, investigation was conducted on the current transformer, and residual flux was measured on positive and negative saturation points along with zero flux point. The average values are 4.001mWb, -3.844mWb and 0.048mWb, respectively. These results show high accuracy and stability of this method. Besides, the rated power of demagnetization voltage source is low which makes the demagnetization devices more portable. © 2017, The editorial office of Transaction of China Electrotechnical Society. All right reserved.


Liu X.,Chongqing University | Yao C.,Chongqing University | Liang S.,Yunnan Electric Power Research Institute | Wang J.,Chongqing University | Liu T.,Yunnan Power Company
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2017

Transformers will have measured no-load excitation characteristics, no-load loss and load loss for factory tests. Generally, a large capacity of industrial-frequency (IF) power supply is needed to measure the no-load loss which mainly consists of core loss. In order to reduce the capacity of testing power supply and make the test equipment portable, a low-frequency power supply rather than IF power supply which was used for core loss measurement of ferromagnetic components, was demonstrated in this paper. By applying several low frequencies voltages, the cure of E/f-PFe (electromotive force/frequency-core loss) via calculating core loss under low-frequency can be first obtained. Core loss under low-frequency of different frequency at constant value of E/f were then calculated through spline interpolation method. Lastly, the converted core loss under IF was determined based on least square method. In addition, experiments were conducted on the current transformer (CT) and single phase power transformer, comparing conversion results which using 15, 20, 25 Hz with directly measured results under IF, the relative error ε is below 5% and standard deviation of relative error σε is less than 0.9, respectively. These results show that this method possesses high conversion accuracy and stability and reduces the capacity of testing power supply obviously. © 2017, The editorial office of Transaction of China Electrotechnical Society. All right reserved.


Zhu X.,Northeast Dianli University | Yu B.,Henan Electric Power Company | Zhang W.,Yunnan Power Company
Proceedings 2011 International Conference on Mechatronic Science, Electric Engineering and Computer, MEC 2011 | Year: 2011

Based on the complex network theory, this paper proposes a weighting parameters based on the voltage and reactance of the transmission lines, and a new method to measure the vulnerability of power grid through the betweenness index. This paper gives a new weight formula and a algorithm to identification of vulnerable lines. The analysis has been carried out on the IEEE5bus system, which confirms the efficacy and practical of the method. © 2011 IEEE.


Sun Q.,Tsinghua University | Shi L.,Tsinghua University | Ni Y.,Tsinghua University | Si D.,Yunnan Power Company
Proceedings of the 2017 18th International Scientific Conference on Electric Power Engineering, EPE 2017 | Year: 2017

This paper aims to identify the critical line on the basis of power system cascading failure search. The proposed critical line identification strategy considers the factors of power flow and topology. Accordingly the electrical betweenness and transmission power are employed during analysis, of which the corresponding theoretical basis is deduced in simple systems. Next follow-up step is to apply the artificial neural network (ANN) technique to classify corresponding degrees. Finally the case studies are performed on the IEEE 39-bus test system to illustrate the validity of the proposed strategies and methods. © 2017 IEEE.


He M.,Shanghai JiaoTong University | Wang F.,Shanghai JiaoTong University | Qian G.,Yunnan Power Company | Yan B.,Yunnan Power Company | Lu Y.,Yunnan Power Company
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2017

To further improve the management rate of working data for power transformer and working efficiency of condition monitoring system in the smart substation, a comprehensive analyzing system of transformer vibration and noise monitoring system is designed and developed based on the actual demand of transformer vibration and noise monitoring, where data management mobile technology and algorithm embedding technology are analyzed. In the proposed system, the Client/Server mode, ADO. NET and MATLAB hybrid programming are adopted with the Oracle database as the background database. Hence, the developed system is capable of reading and storing the massive monitoring data of vibration and noise with high efficiency. Moreover, vibration and noise signals processing algorithms are embedded to extract the features of the monitored signals of transformer under stable operation and sudden short-circuit impact, which is helpful to condition assessment of the transformer in operation. The operation results of the developed system have verified its feasibility and effectiveness. © 2017 Automation of Electric Power Systems Press.


Qian G.Q.,Yunnan Power Company | Lu Y.,Yunnan Power Company | Wang F.H.,Shanghai JiaoTong University | He M.Z.,Shanghai JiaoTong University
Proceedings of the IEEE Power Engineering Society Transmission and Distribution Conference | Year: 2016

Power transformers are always vibrated while working in power system. Those vibration signals are closely related to the mechanical properties of transformer winding. This paper deals with the harmonic response analysis of transformer winding based on finite element method to explore its inherent vibration feature, where a 3-dimensional model of some 10kV transformer winding is built. The frequency response of transformer winding under normal condition and typical fault conditions are analyzed. The modal experiment of transformer winding is designed and made for verification. It is seen that the calculated results of frequency response of transformer winding are agreed well with the measured results. There are four apparent peak in frequency response curve corresponding to the first four order natural frequency of transformer winding. When the winding is loosened or deformed, the peak and the corresponding frequency in frequency response curve are also changed. © 2016 IEEE.


Yan B.,Yunnan Power Company | Qian G.Q.,Yunnan Power Company | Wang F.H.,Shanghai JiaoTong University | Chen S.,Shanghai JiaoTong University
Proceedings of the IEEE Power Engineering Society Transmission and Distribution Conference | Year: 2016

This paper presents a new method to recognize the noise characteristics of power transformer. First, frame division and windowing are applied to pre-process the noise signals. Then Mel Frequency Cepstrum Coefficient (MFCC) combined with Principal Component Analysis (PCA) is proposed to calculate the feature vectors of noise signals for high accuracy. Finally, the vector quantization (VQ) models are built to recognize the noise characteristics. The noise signals of some 10kV transformer are measured when the core is loosened in different degree. It is shown that the proposed MFCC is capable of describing the noise features of transformer accurately. The results of noise recognition by VQ are agreed well with the preset condition of core. The obtained results are helpful for the optimum design and mechanical condition assessment of power transformer. © 2016 IEEE.


Meng G.,Wuhan University | Meng G.,State Grid Electric Power Research Institute of China | Wen X.,Wuhan University | Deng W.,State Grid Electric Power Research Institute of China | And 3 more authors.
Gaodianya Jishu/High Voltage Engineering | Year: 2013

Phase-to-phase switching impulse discharge characteristics play an important role in the design of substation equipment. In order to get the design foundation of 500 kV substations at high altitudes in China, taking into account of 500 kV Jiantang transmission project in Yunnan Province, we practically simulated and tested phase-to-phase switching impulse discharges between flexible buses or grading rings and a typical electrode pair in 500 kV substations. The experiments were performed in 3 areas at different altitude: Wuhan 23 m, Xining 2254 m and Dawu 3742 m, in which phase-to-phase switching impulse discharge curves for gaps of 5~8 m were obtained using the up-and-down method. The influences of voltage distribution coefficients on the gas insulation of phase-to-phase gaps were analyzed, and the experimental results were corrected for the altitudes and then comparatively analyzed. It is concluded that the discharge voltage of air gap decreases sharply with increasing altitude, meanwhile, U50, the 50% switching impulse discharge voltage of phase-to-phase insulation, increases with the voltage distribution coefficient. According to a comparison among several altitude-correction methods, the method in IEC 60071-2-1996 and the m-factor involved altitude-correction method are suggested for phase-to-phase switching impulse's altitude corrections of grading rings and flexible buses in 500 kV substations at high altitudes, respectively.


Meng G.,Wuhan University | Meng G.,State Grid Electric Power Research Institute of China | Wen X.,Wuhan University | Deng W.,State Grid Electric Power Research Institute of China | And 3 more authors.
Gaodianya Jishu/High Voltage Engineering | Year: 2013

In order to get the design foundation of 500 kV substations at high altitudes in China, we employed the up-and-down method to investigate the switching impulse and lightning impulse discharge characteristics of typical simulation frameworks of 500 kV substation at three altitudes (Wuhan 23 m, Xining 2 254 m, Dawu 3742 m) by combining with 500 kV Jiangtang transmission project in Yunnan Province. Switching impulse and lightning impulse discharge curves were obtained with phase-ground gaps of 3~6 m, and several altitude correction methods were used to calibrate and analyze the results so as to give the appropriate correction method for Jiangtang transmission project. The experiments show that the 50% lightning impulse voltages and 50% switching impulse voltages decline with increasing altitudes, but the trend and level of changes have notable differences. Meanwhile, the saturation 50% switching impulse voltage curve is more significant with increasing gaps. According to comparison among altitude-correcting methods, it is concluded that IEC 60071-2: 1996 is suited for correcting lightning impulses of 500 kV substations, and the correction method containing m factor is suited for correcting switching impulses in phase-ground gaps.


Xiong X.-F.,Chongqing University of Technology | Gong X.-F.,Chongqing University of Technology | Wang Y.-X.,Yunnan Power Company
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2013

Meteorological factors will cause the transmission line fault and affect the power system reliability prominently. The original reliability parameter model which considered the meteorological factors is improved, and it is pointed out that transmission lines in different geography have different average failure rate, and their corresponding three kinds of weather and the percentage of number of failures under the three kinds of weather also show great difference. Connection number is used to deal with the uncertainty of reliability original data and weather conditions. RBTS is evaluated with state enumeration method, and the reliability indices in form of connection number are obtained. The result shows that the uneven geography and meteorology will affect the reliability evaluation of the transmission system greatly, and the reliability indices in form of connection number also give the uncertain part, which proves the reliability of the proposed method.

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