Lightning Protection

This review paper, prepared for this second special issue on lightning of the IEEE Transactions on Electromagnetic Compatibility, summarizes major publications on lightning and lightning protection since the first special issue published in November 1998, i.e., during the last decade. The review is organized in the following five sections: lightning discharge-observations, lightning discharge-modeling, lightning occurrence characteristics/lightning locating systems, lightning electromagnetic pulse and lightning-induced effects, and protection against lightning-induced effects.

The salient issues related to lightning protection of long wind-turbine blades are discussed in this paper. We show that the lightning protection of modern wind turbines presents a number of new challenges due to the geometrical, electrical, and mechanical particularities of the turbines. The risk assessment for the lightning-protection-system design is solely based today on downward flashes. We show in this paper that the majority of the strikes to modern turbines are expected to be upward lightning. Neglecting upward flashes, as implicitly done by the International Electrotechnical Commission, might result in an important underestimation of the actual number of strikes to a tall wind turbine. In addition, we show that the rotation of the blades may have a considerable influence on the number of strikes to modern wind turbines as these may be triggering their own lightning. Because wind turbines are tall structures, the lightning currents that are injected by return strokes into the turbines will be affected by reflections at the top, bottom, and junction of the blades with the static base of the turbine. This is of capital importance when calculating the protection of internal circuitry that may be affected by magnetically induced electromotive forces that depend directly on the characteristics of the current in the turbine. The presence of carbon-reinforced plastics (CRP) in the blades introduces a new set of problems to be dealt with in the design of the turbines' lightning protection system. One problem is the mechanical stress resulting from the energy dissipation in CRP laminates due to the circulation of eddy currents. We evaluate in this paper the dissipated energy and propose recommendations as to the number of down conductors and their orientation with respect to the CRP laminates so that the dissipated energy is minimized. It is also emphasized that the high static fields under thunderclouds might have an influence on the moving carbon-fiber parts. This issue needs to be addressed by lightning protection researchers and engineers. Representative full-scale blade tests are still complex because lightning currents from an impulse current generator are conditioned to the electrical characteristics of the element under test and return paths. It is therefore desirable to complement laboratory tests with theoretical and computer modeling for the estimation of fields, currents, and voltages within the blades.

We have analyzed the electric field changes of 14 upward leaders that were initiated from a windmill and its lightning protection tower. We found that these upward leaders can be sub‐classified into two types according to whether they are triggered by nearby lightning discharge activity or they are initiated without any nearby preceding discharge activities. We have also obtained evidence of upward aborted leaders that are initiated from high‐grounded objects in response to nearby lightning. All these results suggest that once the electric field which surrounds the high‐grounded object is large enough, an upward leader can be initiated no matter whether the electric field is built up slowly or created rapidly by a nearby lightning discharge, although the later appears to be more efficient in triggering the leader. In addition, we found that without the assistance of a rising electric field produced by a nearby lightning discharge, compared to a stationary windmill and a tower with a similar height, a rotating windmill tends to have a bigger chance of initiating an upward leader.

Lightning causes deaths, injuries, damages, and significant costs and losses around the world. The global lightning flash rate is in the range of 40 to 100 lightning flashes per second, of which about 30 % are cloud-to-ground flashes. The development of theoretical and experimental researches is crucial for a better understanding of the physical phenomenon and for the characterization of lightning parameters, as well as for the development of more effective methods for lightning protection of structures and systems.

A wind turbine generator is the most exposed of all types of generators connected to electric utility systems. Wind turbines are most often erected in hostile lightning environments. Lightning damage to wind turbines is costly in terms of repair and replacement of equipment. Lightning damage is the single largest cause of unplanned downtime in wind turbines, and that downtime is responsible for the loss of countless megawatts of power generation. There is currently no international standard governing wind turbine lightning protection. This paper offers guidelines for effective protection

The protection of wind turbines from lightning damage is increasingly important as they increase in size and are placed in locations where access to carry out repairs may be difficult. As blades are the most common attachment point of lightning, they must be adequately protected. In addition, the passage of lightning current through wind turbine bearings introduces a risk of lightning damage to these vital components. Investigations relating to the improvement of blade lightning protection systems have been carried out, including experiments designed to address the difficult problems involved in the protection of hydraulic cylinders used for tip brake control. Work has also focused on the ability of lightning current to cause damage to wind turbine bearings. The work has been a mixture of computer simulations and experimental testing using high-voltage and high-current facilities. Copyright © 2001 John Wiley & Sons, Ltd.

The conventional technique for the lightning protection of structures is described in the U.S. National Standard, NFPA 780, and in many other national and international lightning protection standards. Two nonconventional techniques, known generically as “lightning elimination” and “early streamer emission,” are claimed by their proponents to be superior to the conventional lightning protection technique. We review the literature on these nonconventional approaches as well as the pertinent lightning literature and conclude that the suggested superiority of the nonconventional techniques over the conventional method is not supported by the available experimental data or by theory.

There are two major protective methods against lightning outages on overhead distribution lines. One is by use of surge arresters and the other is by an overhead ground wire. Surge arresters have rather constant effect regardless of the type of lightning outage causes. On the other hand, the effect of an overhead ground wire is quite different against the two major causes: direct lightning hit and induced overvoltages. This paper shows how to design lightning protection for overhead power distribution lines taking these characteristics into account. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Lightning and lightning induced effects have significant influence on many aspects affecting the public, which makes the research of lightning and lightning protection very important. However, due to the strong randomness and complex discharge mechanisms of lightning, the understanding of lightning is still far from satisfactory. On the basis of the International Conference on Lightning Protection 2014, this study gives a review of recent progress on lightning and lightning protection research covering the following aspects: lightning locating and observation, lightning physics, lightning electromagnetic transients, and lightning protection for various systems. The goals of this study are to give readers an overall introduction to the recent progress in lightning and lightning protection research, and to motivate them to conduct further studies to address the unsolved problems in lightning-related research.

Abstract : This handbook will assist aircraft design, manufacturing, and certification organizations in protecting aircraft against the direct and indirect effects of lightning strikes, in compliance with Federal Aviation Regulations. It presents a comprehensive text to provide the essential information for the in-flight lightning protection of all types of fixed/rotary wing and powered lift aircraft of conventional, composite, and mixed construction and their electrical and fuel systems. The handbook contains chapters on the natural phenomenon of lightning, the interaction between the aircraft and the electrically charged atmosphere, the mechanism of the lightning strike, and the interaction with the airframe, wiring, and fuel system. Further chapters cover details of designing for optimum protection; the physics behind the voltages, currents, and electromagnetic fields developed by the strike; and shielding techniques and damage analysis. The handbook ends with discussion of test and analytical techniques for determining the adequacy of a given protection scheme. Keywords: Lightning protection, Fuel vapor ignition, Fuel system safety, Atmospheric electrical hazards, Lightning safety, Lightning simulation, Aircraft certification, Atmospheric electromagnetism, Induced currents & voltages, Electromagnetic shielding.