An experimental test of a theory of lightning-induced voltages onan overhead wire

Measured and calculated voltages induced on an unenergized overhead power line by lightning return strokes at distances greater than 5 km from the line are presented. The experiment was performed at the NASA Kennedy Space Center during the summer of 1985 and involved the simultaneous measurement of the voltage induced at one end of the top phase of a three-phase power line and the two horizontal components of the return-stroke magnetic field incident on the line. The effective ground conductivity was determined from previous simultaneous measurements of the vertical and horizontal electric fields. Experiments were performed for two cases: (1) all phases of the power line open-circuited, and (2) one end of the top line terminated at 600 Ω with the other end open-circuited and the other two phases open-circuited at both ends. The waveshapes of the measured and calculated voltages are in reasonably good agreement, and the reasons for observed discrepancies are discussed     

Transient electric and magnetic fields associated with establishinga finite electrostatic dipole, revisited

The authors reexamine the analysis of M.J. Master and M.A. Uman (1983), who derived and plotted the electromagnetic field waveforms generated by a square wave of current propagating with constant speed along a finite linear path, resulting in the formation of a finite electrostatic dipole. It was concluded that such a square pulse of current had charge only at its front and rear. The authors argue that errors were made in that analysis, correct these errors, and extend the overall analysis: (1) to show that the decomposition of the electromagnetic fields into electrostatic, induction, and radiation components on the basis of distance dependence is not general; (2) to demonstrate the use of the continuity equation in finding the charge distribution along a current path when the current distribution is known; and (3) to show how a seemingly simple analytical technique, the treatment of an abrupt step of current as a linearly rising current in the limit that the risetime goes to zero, can lead to erroneous results if there is not a good physical and mathematical understanding of all the variables involved     

Lightning-induced voltages at both ends of a 448-mpower-distribution line

Lightning-induced voltages due to return strokes in ground flashes beyond about 5 km were measured simultaneously at both ends of an unenergized 448-m power-distribution line. The measurements represent an extension of an earlier experiment on the same line in which voltages are obtained at only one end of the line. In addition to the induced voltage measurements, the causative lightning electric and magnetic fields are recorded. The voltage and field measurements are made as a function of the lightning direction and of the power-line termination. For both measured and idealized electric fields as inputs to a time-domain transmission-line coupling model, the authors calculate line voltages as a function of the incident angle of the lightning electromagnetic radiation and of the line termination. Measured and predicted voltages calculated from the coupling model with measured fields as inputs show, overall, good agreement in waveshape, but the predicted voltages are about a factor of three larger in amplitude. To the extent that the results can be compared, there is reasonable agreement with the earlier experiments on the same line     

Burst of pulses in lightning electromagnetic radiation:observations and implications for lightning test standards

Bursts of regular microsecond-scale electric field pulses produced by three multiple-stroke cloud-to-ground discharges (a total of 2782 pulses) and by three cloud discharges (a total of 1436 pulses), all recorded within 20 km or so at the NASA Kennedy Space Center, are analyzed. The regular pulse bursts are similar in both cloud-to-ground and cloud discharges. A burst is characterized by some tens of pulses, each having a total width of a few microseconds, with an average interpulse interval of 6-7 μm. Pulse peaks in cloud-to-ground discharges are approximately two orders of magnitude smaller than return-stroke initial field peaks in the same flash. In both cloud and ground discharges, there is a tendency for the bursts to occur in the latter stages of a discharge, and positive and negative pulse polarities are about equally probable. Many bursts were found to be associated with the latter part of K changes while one pronounced M change appeared to be initiated by a regular pulse burst. The observed regular burst exhibit some similarity to the “multiple burst” (component H) of the standard lightning environment for the design and testing of aerospace vehicles. Overall, neither the present definition of the H component given in a previously published document (see Fed. Aviation Admin., US Dept. of Trans., advisory circular no. 20-136, Mar. 5, 1990) nor its newly proposed revision appears to be based on adequate experimental data     

Natural and artificially-initiated lightning and lightning teststandards

Present understanding of both natural and artificially initiated lightning is first reviewed. The ways in which lightning can cause damage, the methods that are used to provide protection from that damage, and the test standards that are used to assess the immunity of systems from lightning damage are then examined. Finally, deficiencies in present approaches to lightning protection are pointed out and recommendations for the amelioration of those deficiencies are given     

Lightning induced disturbances in buried cables - part II: experiment and model validation

This paper presents experimental results obtained at the International Center for Lightning Research and Testing (ICLRT) at Camp Blanding, Florida during the summers of 2002 and 2003. Currents induced by triggered and natural lightning events were measured at the terminations of a buried power cable, in the cable shield, and in the inner cable conductor. Measurements of the horizontal component of the magnetic field above the ground surface for both natural and triggered lightning are also presented. For distant natural lightning events, locations of ground strike points were determined using the U.S. National Lightning Detection Network (NLDN). Based on the theoretical developments presented in Part I of this paper , the field-to-buried cable coupling equations are solved in both the time domain and in the frequency domain. The obtained experimental results are then used to validate the numerical simulations provided by the relevant developed codes.     

居民区雷电保护系统的试验:火箭触发雷电和电流冲击发生器试验数据的比较(英文)

We present a comparison of data obtained during testing of lightning protective system of a residential structure in rocket-triggered lightning experiment at the International Center for Lightning Research and Testing(ICLRT)at Camp Blanding,Florida,and current surge generator experiment at Rzeszow University of Technology in Poland.Three different configurations of LPS were tested in Poland with the dc grounding resistances of the entire system 4.09 Ω(LPS 1a),1.65 Ω(LPS 1b),and 2.88 Ω(LPS 2).For LPS 1a with three ground rods the value of the peak current entering the electrical circuit neutral was about 56% of the injected current peak,and for LPS 1b with two additional ground rods and two 5 m long buried horizontal conductors it was about 16%.For LPS 2 with five ground rods interconnected by a buried loop conductor this ratio was 21%.The current waveshapes in the ground rods differed from the injected current waveshapes and the current waveshapes in other parts of the test system,especially,for poorer-grounding LPS 1a.The surge-generator results are consistent with those of triggered-lightning experiments at Camp Blanding,Florida(DeCarlo et al.,2008 [2]).     

Recent advances in shear-thinning and self-healing hydrogels for biomedical applications

Shear-thinning and self-healing hydrogels are being investigated in various biomedical applications including drug delivery, tissue engineering, and 3D bioprinting. Such hydrogels are formed through dynamic and reversible interactions between polymers or polypeptides that allow these shear-thinning and self-healing properties, including physical associations (e.g., hydrogen bonds, guest–host interactions, biorecognition motifs, hydrophobicity, electrostatics, and metal–ligand coordination) and dynamic covalent chemistry (e.g., Schiff base, oxime chemistry, disulfide bonds, and reversible Diels–Alder). Their shear-thinning properties allow for injectability, as the hydrogel exhibits viscous flow under shear, and their self-healing nature allows for stabilization when shear is removed. Hydrogels can be formulated as uniform polymer and polypeptide assemblies, as hydrogel nanocomposites, or in granular hydrogel form. This review focuses on recent advances in shear-thinning and self-healing hydrogels that are promising for biomedical applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48668.     

Performance of MOV arresters during very close, direct lightningstrikes to a power distribution system

In 1996, at the International Center for Lightning Research and Testing (ICLRT) at Camp Blanding, Florida, the responses of MOV arresters in an unenergized test distribution system, composed of an overhead line, underground cable, and padmount transformer with a resistive load, were measured during very close, direct lightning strikes to the overhead line. Arresters were installed on the overhead line at two locations 50 m apart (on either side of the strike point) and at the primary of the padmount transformer which was connected to the line via the underground cable. We obtained arrester data for this test configuration from two lightning flashes (containing a total of five strokes) which were artificially initiated from a natural thunderstorm, using the rocket-and-wire technique. We present the simultaneously-recorded arrester discharge current and voltage waveforms from one lightning stroke for one of the two arresters on the line and for the arrester at the transformer primary. Additionally, we estimate the energy absorbed by the arrester on the line as a function of time for the first 4 ms of the lightning event. The records presented are representative of those for all five strokes     

EMP susceptibility insights from aircraft exposure to lightning

Examines the interactions of natural lightning and the nuclear electromagnetic pulse (EMP) with aircraft. The propositions that one can use normal exposure to lightning to provide information on EMP protection, and deliberate exposure to lightning to test EMP protection are evaluated. The rarity of encountering lightning, its random occurrence and variability (necessitating extensive onboard instrumentation), and its apparent deficiency in energy at the high frequencies make the use of lightning for an EMP surveillance or test impractical