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Li J.,Chongqing Lightning Disaster Identification and Protection Project Engineering Research Center | Li J.,Chongqing Lightning Protection Center | Luan J.,Liaoning Lightning Protection Technical Service Center | Wang P.,Liaoning Lightning Protection Technical Service Center | And 2 more authors.
Gaodianya Jishu/High Voltage Engineering | Year: 2014

To analyze and use the data of lightning location system (LLS), it is necessary to perform quality control of the data, for example, excluding some small amplitude cloud-to-cloud lightning which is inevitably mistaken to cloud-to-ground lightning (CG) by LLS. Using the lognormal distribution function, we performed fitting and analysis of the data obtained by a lightning location system in Chongqing, China from 1999 to 2008. It is found that by ignoring the data of lightning with amplitudes less than 5 kA (which occupies 1.05% of the total data), we obtained the best fitting result that passes the test of statistical significance and reflects the statistical characteristic of CG. We also analyzed the variation of frequency distribution and proportion of different region of small amplitude CG, and found that ignoring the CG data blow 5 kA not only accords with the error feature of LLS, but also reflects the effect of upgrading LLS devices in decreasing deviation. Therefore, we delimit the "small amplitude" of lightning in Chongqing as below 5 kA. The result could be referred by researches of "small amplitude" lightning and quality control LLS data for other geographic regions. Source


Du L.,Chongqing University | Yu S.,Chongqing University | Mi X.,Chongqing Lightning Protection Center | Yang Q.,Chongqing University | Wang Y.,Chongqing University
Przeglad Elektrotechniczny | Year: 2012

To analyze exactly the wave propagation processes of a transmission tower when lightning strikes, an equivalent model of a transmission tower was studied in this paper. First, based on the correlative theory of tapered antenna, an equivalent surge impedance model of a single stanchion of tower was made. This tower was regarded as a four-conductor system according to the real configuration of a tower, and the equivalent impedance of the four-conductor system was obtained by multiplying the single pillar impedance with the compensation factor. Combined with the definition of wave impedance regarded with inductance and capacitance, the compensation factor of the four-conductor system was introduced. Then, the bracings equivalent model was obtained based on the analysis of the effect of bracings on the main body of a tower, and an equivalent impedance model of the crossarms was built base on the correlation theory of the equivalent model of parallel multi-conductors. In modularizing the tower model, the equivalent impedance of the tower was found. Finally, a 500 kV tower was calculated in this paper using the equivalent impedance model of the tower. Source


Li Y.-F.,Chongqing University | Sima W.-X.,Chongqing University | Chen L.,Chongqing University | Yang M.,Chongqing University | Qin B.-Q.,Chongqing Lightning Protection Center
Gaodianya Jishu/High Voltage Engineering | Year: 2011

We adopted global digital elevation data to complete the elevation information of lightning detection data in some region of China, from 2007 to 2010. Furthermore, we also adopted 3D lightning detection data to investigate the law of lightning current amplitude, ground flash density(GFD) and proportion of positive flash with the change of elevation. The results are as follows: the height of thunderstorm base above ground decreases with the increasing of elevation, and upgoing lightning current amplitude is generally low in mountains, so the lightning current amplitudes of both positive flash and negative flash increase with the increasing of elevation. Relationship between elevation and logarithm of mean of lightning current amplitude is expressed by fitting lines. Ground flash density of negative flash decreases sharply with the increasing of elevation, which makes GFD of negative flash in high altitude region to be the only 1/3 of GFD of negative flash in low altitude region. On the contrary, GFD of positive flash increases with the increasing of elevation. With the increasing of elevation, the proportion of positive flashes increases by 300%. Besides, water area obviously affects the lightning current, which may be the reason of the diversity of lightning current statistic results from high altitude and low altitude regions. Source


Du L.,Chongqing University | Mi X.,Chongqing University | Mi X.,Chongqing Lightning Protection Center | Xiao Z.,Chongqing University | And 4 more authors.
Gaodianya Jishu/High Voltage Engineering | Year: 2012

In order to analyze the wave processes in the transmission tower struck by lightning, we studied equivalent models of cross arm and inclined holder based on an existing equivalent transmission tower model. The theory of parallel multi-conductor was applied to study the equivalent tower cross arm model. The equivalent inclined holder model was derived by multiply a compensation factor of inclined holder on the equivalent impedance model of tower main body. Meanwhile, the compensation factor of inclined holder was constituted by the capacitance and inductance compensation factor which were obtained by calculating the variation of electric field energy and magnetic field energy caused by inclined holder. The values of the capacitance and inductance compensation factor were 0.9895 and 0.8360, respectively, and the compensation factor of inclined holder turned out to be 0.8272. Moreover, according to the calculation method of the equivalent impedance models of cross arm and inclined holder, the equivalent impedance model of a 500 kV SZC3 tower was established to analyze its surge process under lightning stroke. Source


Sima W.,Chongqing University | Li Y.,Chongqing University | Yang Q.,Chongqing University | Yuan T.,Chongqing University | Qin B.,Chongqing Lightning Protection Center
Gaodianya Jishu/High Voltage Engineering | Year: 2012

To deal with disadvantages that the credibility and spatial resolution of lightning parameters calculated by traditional grid method (TGM) are not high enough, we proposed an improved grid method (IGM). IGM substitutes a couple of parameters (grid area and monitored radius) for the single parameter (grid area) in TGM. Taking lightning data recorded by lightning location system in Chongqing as an example, we illustrate the differences of the two methods in the statistics of thunderstorm day, thunderstorm hour and ground flash density. The results show that the three kinds of lightning parameters don't change sharply with the improvement of spatial resolution by the method of IGM, and the physics meanings of lightning parameters gained by means of IGM are clearer than the ones by means of TGM. Therefore, compared with the TGM, the spatial resolution and credibility of lightning parameters calculated by IGM is better, which can provide a good support for the differentiated lightning protection design. Source

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