Laiwu Electrical Power Company

Laiwu, China

Laiwu Electrical Power Company

Laiwu, China
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Zhan H.,North China Electrical Power University | Liu B.,State Grid Corporation of China | Shi W.,Shandong University | Yan T.,Laiwu Electrical Power Company | Li C.,North China Electrical Power University
Gaoya Dianqi/High Voltage Apparatus | Year: 2014

Shielding failure is the main factor for lightning trip-out of EHV and UHV transmission lines, and space charge plays an important role in the shielding failure accident. In order to investigate the influence of space charge on lightning discharge, a rod-line air gap of 150 cm in length was set up. Under the positive and negative switching impulse voltage, the discharge process of the gap was observed by a high speed video camera system and statistical analysis on the number of strikes on the line electrode with different diameter was performed. The current flowing through the positive rod-line air gap was measured to obtain the charge current, and the integral of the charge current was calculated to evaluate the amount of space charge. The influence of space charge on the electric field in the vicinity of the line electrode was explored through the ANSYS. Experimental results showed that shielding effect of space charge on discharge strike point is significant under positive switching impulse voltage, but under negative switching impulse voltage, this shielding effect is not a leading factor influencing strike number and discharge path. The shielding effect of space charge is related with the size of line electrode. The larger the line electrode diameter is, the smaller the shielding effect of space charge becomes.


Cheng X.,Beijing Electrical Power Research Institute | Yan T.,Laiwu Electrical Power Company | Zhan H.,North China Electrical Power University | Wang L.,North China Electrical Power University | And 3 more authors.
Gaoya Dianqi/High Voltage Apparatus | Year: 2014

A sensor positioned at the sprue in metal flange of an insulator can receive UHF signals radiated from GIS for analyzing the characteristics of partial discharge. To understand the effects of the sprue size on the propagation of UHF electromagnetic waves, the finite difference time domain (FDTD) method is used for modeling. The characteristics of the time domain and frequency domain parameters of the UHF waves in the middle of the sprues with different sizes are investigated. Moreover, some experiments are conducted to verify the effectiveness of the simulation. The results show that the field strength component along the conductor is much stronger than the components of other two directions, and that the larger the sprue size, the stronger the signals radiating from the sprue, in which low frequency components (500-900 MHz) occupy a large proportion.


Zhan H.,North China Electrical Power University | Liu B.,State Grid Corporation of China | Yan T.,Laiwu Electrical Power Company | Deng L.,Institute of Urban Construction | Li C.,North China Electrical Power University
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2014

Shielding failure is the main reason for tripping operations of EHV and UHV transmission lines, and many scholars believe that space charge may be one of the causes of these shielding failure accidents. In order to further study the influence of space charge on lightning discharge, a board-needle air gap of 100cm was set up. Under the positive and negative switching impulse voltage, the discharge process of the gap was observed by a high speed video camera system. So as to analyze the influence of the space charge on the discharge development quantitatively, the current through the positive board-needle air gap was measured. Then the charge current was extracted, and the integral of the charge current was calculated to evaluate the amount of space charge. Experimental results show that discharge always develops from the positive electrode to the negative electrode, under both positive and negative switching impulse voltage. Besides, under the positive switching impulse voltage, with the radius of curvature of the head part of the needle increasing, the percentage of discharge striking points on the head of the needle decreases. What's more, under the same test conditions, the amount of the space charge of the board-pointed needle is the largest. With the radius of curvature of the head part of the needle increasing, the amount of the space charge becomes smaller.


Li Q.,Shandong University | Xu G.,Shandong University | Xu G.,Shandong Electric Power Research Institute | Fang X.,Shandong University | And 2 more authors.
Gaodianya Jishu/High Voltage Engineering | Year: 2012

Compared with the parallel-plate dielectric barrier discharge, surface dielectric barrier discharge (SDBD) can produce uniform plasma layer with a larger area, and it has also been mainly applied in such new technologies as the flow control, all of that have drawn a wide attention from the academia and the industry. In order to better research the discharge mechanism and the regularity of evolution of SDBD, we performed the two-dimensional numerical simulation of SDBD in the air with the plasma module of Comsol. In the process of air discharge, considering the chemical reaction of 8 kinds of particles, such as O 2 -, N 2 -, and O 2 + , and 16 discharge chemical reactions, we got the change process of particle concentration and the electric-field distribution in the discharge space. By analyzing and discussing the movement of electric charge in the initial phase, we find that, electron, mainly controlled by the electric field in the initial stage, will do drift motions, then its scope of distribution will be expanded which is affected by both diffusion and drift motions. Moreover, the asymmetry of discharge is analyzed and verified, and it is pointed out that the accumulation of charge on the surface leads to the asymmetry of discharge.


Zhao R.-D.,China University of Petroleum - East China | Ma S.,China University of Petroleum - East China | Ma S.,Laiwu Electrical Power Corporation | Li H.-J.,China University of Petroleum - East China | Wu X.-B.,China University of Petroleum - East China
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2013

Frequency plays an important role in power system protection and control, power quality monitoring and other fields. The complex state space description of the voltage signal under harmonics and noise is established, then the strong tracking filter (STF) based frequency-measuring algorithm for power system is proposed. It is not necessary to reset the error covariance matrix for STF as it is for extended complex Kalman filter (ECKF) algorithm to track the sudden state mutation of power system after initial convergence, thus significantly improving its tracking speed. Results of comparative simulation studies of the proposed algorithm with robust extended complex kalman filter (RECKF) algorithm show that the STF-based algorithm is able to quickly track the frequency, amplitude and phase changes while maintaining a considerably low tracking error.


Zhao B.,Laiwu Electrical Power Company | Zhao X.,Laiwu Electrical Power Company | Wang C.,Laiwu Electrical Power Company | Tian C.,Laiwu Electrical Power Company | And 2 more authors.
Applied Mechanics and Materials | Year: 2013

The weight of evaluation index plays a key role in condition assessment and maintenance control of power transformer. A new approach of determination of comprehensive weight is proposed in this paper. The approach combines the entropy objective weight with the expert subjective weight together in a specific form, which not only avoids the situation that single weight determines the overall weight, but considers the primary and secondary problem between the two weights. The comprehensive weight calculated by this approach can reflect the place of every index in condition assessment of power transformer well. Empirical results show that the approach is reasonable and available. © (2013) Trans Tech Publications, Switzerland.

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