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Zheng D.,Chinese Academy of Meteorological Sciences | Zheng D.,Guangzhou Field Experiment Site for Lightning Research and Testing | Zhang Y.,Chinese Academy of Meteorological Sciences | Zhang Y.,Guangzhou Field Experiment Site for Lightning Research and Testing | And 8 more authors.
Atmospheric Research

The currents of 29 return strokes (RSs) involved in 10 classical triggered lightning flashes (TLFs) and an altitude TLF conducted in Guangdong, China from 2008 to 2011 are analyzed for the first time. They have relatively greater peak values (geometric mean (GM) of 16.07kA), average rate of rise between 10 and 90% (S10-90%, GM of 29.16kAμs-1), charge transfer within 1ms (Q1ms, GM of 1.36 C) and action integral within 1ms (AI1ms, GM of 5.39×103A2s), compared with those reported in other studies. The current peak value exhibits pronounced exponential relation with S10-90% (determination coefficient (R2)=0.43) and maximum rate of rise (R2=0.77), power relation with Q1ms (R2=0.89), and logarithmic relation with AI1ms (R2=0.93). Additionally, the discharges associated with the processes of initial-stage return strokes (ISRSs) involved in two altitude TLFs, with the peak currents of 10.09kA and 9.03kA, respectively, are investigated. Their peak, 10-90% risetime, average rate of rise between 10 and 90% and maximum rate of rise are comparable to those of the RSs. The chopped-shape pulses closely following the ISRSs and the pulses associated with the disintegration and reconnections of the wire's channel are also discussed. © 2012 Elsevier B.V. Source

Cui X.,Jiangsu Lightning Protection Center | Zhuang Y.,Guangdong Lightning Protection Center | Wang H.,Jiangsu Lightning Protection Center
Journal of Natural Disasters

Under the guidance of "pressure-state-response" (PSR) conceptual framework model, a set of index system of lightning disaster risk zoning was designed, which was used to conduct a empirical analysis with Jiangsu Province as an example. This is the first time that the concept of entropy is introduced to the lightning risk zoning. Three methods, the entropy method, the principal component analysis method, and the analytic hierarchy process, were used on the same sets of data to determine the weights of eight indices. By calculating Spearman correlation coefficient, the closeness of the three different evaluation methods was researched. The results showed that, there existed a high correlation among the three methods. Its feasible to combine and reorder the results by using combined evaluation method. The very high risk areas of lightning in Jiangsu Province are located in Suzhou, Wuxi, Nanjing and Nantong; the high risk areas of lightning are located in Changzhou, Xuzhou and Yangzhou; the medium risk areas of lightning are located in Yancheng, Taizhou and Zhenjiang; the low risk areas of lightening are located in Huaian, Lianyungang and Suqian. The zoning results could give an important reference to disaster prevention and mitigation decisions. Source

Zheng D.,Chinese Academy of Meteorological Sciences | Zheng D.,Guangzhou Field Experiment Site for Lightning Research and Testing | Zhang Y.,Chinese Academy of Meteorological Sciences | Zhang Y.,Guangzhou Field Experiment Site for Lightning Research and Testing | And 10 more authors.
Acta Meteorologica Sinica

This study investigates an abnormal artificially triggered lightning event that produced two positive upward propagations: one during the initial stage (i.e., the upward leader (UL)) and the other after a negative downward aborted leader (DAL). The triggered lightning was induced in a weak thunderstorm over the experiment site and did not produce a return stroke. All of the intra-cloud lightning around the experiment site produced positive changes in the electric field. The initial stage was a weak discharge process. A downward dart leader propagated along the channel produced by the first UL, ending at a height of approximately 453 m and forming a DAL. Under the influence of the DAL, the electric field at a point located 78 m from the rod experienced a steady reduction of about 6.8 kV m-1 over 5.24 ms prior to the initiation of a new upward channel (i.e., the second upward propagation (UP)). The second UP, which started approximately 4.1 ms after the termination of the DAL and propagated along the original channel, was triggered by the DAL and sustained for approximately 2.95 ms. Two distinct current pulses were superimposed on the current of the second UP. The first pulse, which was related to the sudden initiation of the second UP, was characterized by a more rapid increase and decrease and a larger peak value than the second pulse, which was related to the development of the second UP into the area affected by the DAL. The second UP contained both a similar-to-leader process and a following neutralization process. This study introduces a new type of triggering leader, in which a new upward discharge is triggered in an established channel by an aborted leader propagating along the same channel with opposite polarity and propagation direction. © The Chinese Meteorological Society and Springer-Verlag Berlin Heidelberg 2012. Source

Wang X.,Guangzhou Meteorological Bureau | Chen S.,Guangdong Lightning Protection Center | Zhang Y.,Chinese Academy of Meteorological Sciences | Huang Z.,Guangdong Lightning Protection Center | Cai L.,Wuhan High Voltage Research Institute
Dianwang Jishu/Power System Technology

The experimental investigation on over-voltage protection for outdoor low-voltage overhead transmission lines is carried out. Based on a typical natural lightning with multi return strokes and combining with lightning location data, the values of over-voltages at entrance terminals for housings and those at front-side of collector, which locate at differnet positions of transmission lines and the residual voltage characteristics of surge protective devices (SPD) located at collector front-side as well as the relation between over-voltages of L-lines at entrance terminals for housings and return stroke current of lightning are analyzed and discussed. Analysis results show that close range lightning can lead to induced over-voltage with amplitude of several kilovolts on low-voltage overhead transmission lines and the duration of this over-voltage is about 1.0 ms in average; after the action of SPDs installed at the front-side of collector the over-voltage waveforms at farther entrance terminals for housings will be influenced, and the duration of residual voltage after the action of SPD is about 218 μs in average, which is longer than the duration from standard 8/20 μs test waveform; and there is good linear fitting relation between induced over-voltages at entrance terminals for housings and the ratio of return stroke currents to return stroke distances. Source

Dai C.,Huawei | Wang Q.,Huawei | Zhang X.,Huawei | Chen S.,Guangdong Lightning Protection Center | Huang Z.,Guangdong Lightning Protection Center
2014 International Conference on Lightning Protection, ICLP 2014

This paper presents a statistical analysis of the characteristics of surge currents measured in a number of cables in a Distribution Base Station (DBS) system when being struck by rocket-triggered lightning. The measurements were conducted in the period from 2011 to 2013 at Guangdong, China. Lightning strikes were triggered through a 6.1m lightning rod at the top of a 15.2 m experimental metallic tower. The DBS equipment was installed partly on the platform near the tower top, and partly inside the cabinet on the ground level. There were some signal/power cables, RF feeder cables, and fibers applied for interconnecting the DBS equipment in both parts. The return-stroke current waveforms were recorded during the lightning current injecting into the metallic tower. Statistical information has been presented for the return-stroke peak current including the parameters of the risetime (10%-90%), the half-peak width, and the charge transfer. Our statistics on the return-stroke current peak are found generally in consistent with those reported from other triggered-lightning studies. In addition, the lightning currents shared into the number of cables were analyzed. The results show that a large part of the return-stroke current flow into the local earthing network through the tower metallic elements. Only a small part of the total injected current is shared into those cables. Next, with this specific or typical AC installation for DBS system, we have found the current level flowing into the AC power installation cables is much lower than the 50% of the total injected lighting current. This fact may remain us to re-consider if the assumption of 50% current sharing at AC installation cable by IEC standard [9] is too high. © 2014 IEEE. Source

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