Lightning arc damage to optical fiber ground wires (OPGW): parameters and test methods
15 Jul 2001-Vol. 1, pp 88-93
TL;DR: The present version of IEEE Standard 1138 gives no guidance regarding the possible damage to OPGW from exposure to lightning as mentioned in this paper, which may not be enough to protect optical fibers from long-term damage.
Abstract: The present version of IEEE Standard 1138 gives no guidance regarding the possible damage to OPGW from exposure to lightning. Industry experience with conventional overhead ground wires has settled on an overall diameter in excess of 12 mm for good long-term mechanical performance. This may not be enough to protect optical fibers from long-term damage. Test specifications, using the existing body of knowledge for calculation of lightning tripout rates, can be derived from existing practice in IEEE Standard 1243, supplemented by empirical fits to observations of the distribution of total flash charge as measured by Berger. Test procedures can also be recommended, based on practical experience obtained using a variety of approaches that include IEEE Standard 4 and IEC 60794.
Citations
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TL;DR: In this article, the authors developed a computational algorithm that analyzes the pixels of the images obtained by a high-speed camera and plots luminosity-versus-time for 63 natural discharges and classified them into six different types.
Abstract: Continuing current is a continuous mode of charge transfer to ground in a lightning flash. The extent to which the continuing current contributes to the total negative charge lowered to earth is large. In order to study the waveshape of the continuing currents of natural flashes, we developed a computational algorithm that analyzes the pixels of the images obtained by a high-speed camera and plots luminosity-versus-time. Tower measurements have shown that during the continuing current phase of the flash the luminosity of the channel is directly proportional to the current that flows through it. Using this information it was possible to infer the continuing current waveshape for 63 natural discharges and classify them into six different types. Statistics on some characteristics of 345 M-components (that occurred during the same 63 events) are also presented. As far as we know, this is the first study on waveshapes of continuing currents for natural lightning.
54 citations
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TL;DR: In this paper, the authors analyzed the wave shape of positive cloud-to-ground (CG) flashes through high-speed GPS synchronized videos and compared the results with data obtained by the Brazilian Lightning Location System (BrasilDAT).
Abstract: This work analyses the waveshapes of continuing currents and parameters of M-components in positive cloud-to-ground (CG) flashes through high-speed GPS synchronized videos. The dataset is composed of only long continuing currents (with duration longer than 40 ms) and was selected from more than 800 flashes recorded in Sao Jose dos Campos (45.864°W, 23.215°S) and Uruguaiana (29.806°W, 57.005°S) in Southeast and South of Brazil, respectively, during 2003 to 2007 summers. The videos are compared with data obtained by the Brazilian Lightning Location System (BrasilDAT) in order to determine the polarity of each flash and select only positive cases. There are only two studies of waveshapes of continuing currents in the literature. One is based on direct current measurements of triggered lightning, in which four different types of waveshapes were observed; and the other is based on measurements of luminosity variations in high-speed videos of CG negative lightning, in which besides the four types above mentioned two additional types were observed. The present work is an extension of the latter, using the same method but now applied to obtain the waveshapes of positive CG lightning. As far as the authors know, this is the first report on M-components in positive continuing currents. We also have used the luminosity-versus-time graphs to observe their occurrence and measure some parameters (duration, elapsed time and time between two successive M-components), whose statistics are presented and compared in detail to the data for negative flashes. We have plotted a histogram of the M-components elapsed time over the total duration of the continuing current for positive flashes, which presented an exponential decay (correlation coefficient: 0.83), similar to what has been observed for negative flashes.
39 citations
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TL;DR: In this paper, the authors presented some parameters of negative cloud-to-ground lightning flashes in terms of frequency distribution, including the number of strokes per flash, time intervals between strokes, and total flash duration.
Abstract: [1] This paper presents some parameters of negative cloud-to-ground lightning flashes in terms of frequency distribution. All data are based on so-called “accurate-stroke-count studies” from different climatological regions in the world and were already published in the literature with the exception of our measurements. We used GPS synchronized data from two digital high-speed cameras (at 1–8,000 frames/sec). The parameters considered in this study are: (1) continuing current duration, (2) time intervals between strokes, (3) number of strokes per flash and (4) total flash duration. The analysis includes Berger's data of Monte San Salvatore (Switzerland), which is the basis for lightning protection standards. The comparison suggests that despite of overall agreement of those parameters that some of them, currently used in protection standards, should be revised in order to be more realistic.
26 citations
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TL;DR: In this article, the effects of lightning and impulse currents on the perturbations of the state of polarization (SOP) of optical beams transmitted on aerial cables are emulated in a laboratory environment.
Abstract: The effects of lightning and impulse currents on the perturbations of the state of polarization (SOP) of optical beams transmitted on aerial cables are emulated in a laboratory environment. Submicrosecond-resolved measurements enable us to distinguish and quantify the magnetooptic contributions due to the discharge current. The maximum of Faraday-induced circular birefringence associated to natural strokes is estimated in /spl Delta/n/sub lr//spl ap/10/sup -7/ and may lead in a few microseconds to iterate swapping between orthogonal SOPs. The corresponding peak in relative phase delay, cumulated in transmission along a span, is evaluated as /spl Delta//spl tau//sub lr//spl ap/0.3 ps.
14 citations
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TL;DR: In this article, the authors presented some CC intensity estimates obtained from an electric field capacitive antenna, and most CC intensities were much higher than the usual intensity values of CC in negative flashes.
Abstract: The highest directly measured lightning currents and the largest charge transfers to ground are thought to be associated with positive lightning. Brook at al. [1] for one positive lightning in a winter storm in Japan, inferred a charge transfer in excess of 300 coulomb (C) during de first 4ms. But charge transfers to beyond 3000C were reported from direct current measurements, by Miyake et al.[1] for positive winter lightning in Japan. Positive strokes may have high peak currents followed by long continuing current (CC), and thus combine these two threatening features for lightning protection. Although positive flashes are usually less frequent than negative lightning, the special characteristics of their CC make the understanding of positive lightning an important issue. Positive lightning were recorded in southeastern Brazil during the summers of 2009–2011. This study presents some CC intensity estimates obtained from an electric field capacitive antenna. Most CC intensities were much higher than the usual intensity values of CC in negative flashes.
8 citations
References
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TL;DR: In this article, the authors measured the time derivative of the electric field of triggered lightning strokes at distances of 10, 14, and 30 m. The data were taken in 1998 at the International Center for Lightning Research and Testing at Camp Blanding, Florida.
Abstract: We have directly measured the time derivative of the electric field of triggered lightning strokes at distances of 10, 14, and 30 m. The data were taken in 1998 at the International Center for Lightning Research and Testing at Camp Blanding, Florida. We compare our results with those of similar triggered lightning measurements made previously at the Kennedy Space Center at distances of 50 m and 5 km and in France at 50 m. We also compare our electric field derivative waveforms with previous measurements at the Kennedy Space Center of natural lightning strokes over the Atlantic Ocean at distances of the order of tens of kilometers and with overland natural lightning data obtained at 0.7 to 14 km in Germany. Our return stroke electric field derivative peak values normalized (assuming the inverse distance dependence valid for radiation fields) to 100 km are similar to all previous measurements for both natural and triggered lightning at distances from 50 m to about 50 km, all being several tens of volts per meter per microsecond, with the exception of the German overland peak derivative values which are an order of magnitude lower. Our 10- to 30-m field derivative zero-to-peak risetimes are typically 50 to 100 ns (minimum of 30 ns and maximum of 180 ns), and widths at half-peak value are typically 100 to 200 ns. There is essentially no difference between our electric field derivative waveshapes measured simultaneously at 10 m and at 30 m, with the closer waveform being about a factor of 2 greater in amplitude. Fourier analysis of our electric field derivative waveforms indicates that the primary frequency content of the waveforms is below about 20 MHz. Our close return stroke field derivative waveforms differ from those of Leteinturier et al. (1990) recorded 50 m from triggered lightning at the Kennedy Space Center in 1985 in that their derivative waveforms typically decrease rapidly after the peak and exhibit zero crossings and in that their waveforms tend to have multiple peaks, while our derivative waveforms are generally single peaked and decay more gradually to zero after the peak, with no zero crossings. We argue that the differences between their waveforms and ours are related to the relatively large rocket-launching structure used at the Kennedy Space Center in 1985.
50 citations
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TL;DR: In this article, the authors present the results of various investigations made in developing lightning-resistant overhead ground wires (GW) and composite fiber optic ground wire (OPGW) applicable for conventional transmission lines.
Abstract: Overhead ground wires (GW) are vulnerable to strand breakage due to lightning strikes. With the wider application of composite fiber optic ground wire (OPGW), it becomes more important to protect GW from such damage. In this paper, the authors present the results of various investigations made in developing lightning-resistant GW/OPGW. Investigations included field experiments using rocket-triggered lightning, studies on materials and designs to improve lightning characteristics and various evaluation tests, such as DC arc tests, of several prototypes. As a result, the authors have developed lightning-resistant GW/OPGW applicable for conventional transmission lines. >
11 citations