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In this chapter, we give an overview of lightning discharges, which can cause electromagnetically induced effects in power and telecommunication systems. Then, we describe modeling of the lightning return stroke and explain “engineering” models, in which the spatial and temporal distribution of the current or the line charge density along the lightning channel is specified based on such observed lightning return-stroke characteristics as current at the channel base, the speed of the upward-propagating front, and the channel luminosity profile. Also, we discuss the equivalency between the lumped-source and distributed source representations, and the extension of engineering models to include a tall grounded strike object. Further, we describe two primary approaches to test lightning return-stroke models that are referred to as “typical-event” and “individual-event” approaches.

In this chapter, basic lightning terminology is introduced, different types of lightning are described, and main lightning processes are identified. For the most common negative cloud -to -ground lightning, the number of strokes per flash, interstroke intervals, flash duration, multiple channel terminations on ground, and relative stroke intensity within the flash are discussed. Traditional lightning parameters needed in engineering applications include lightning peak current, maximum current derivative, average current rate of rise, current risetime, current duration, charge transfer, and specific energy (action integral), all derivable from direct current measurements.

Electromagnetic computation methods (ECMs) have been widely used in analyzing lightning electromagnetic pulses (LEMPs) and lightning-caused surges in various systems. One of the advantages of ECMs, in comparison with circuit simulation methods, is that they allow a self-consistent, full-wave solution for both the transient current distribution in a three-dimensional conductor system and resultant electromagnetic fields, although they are computationally expensive. Among ECMs, the finite-difference time-domain (FDTD) method has been the most frequently used in lightning electromagnetic field and surge simulations. In this chapter, applications of the FDTD method to lightning electromagnetic field and surge simulations are reviewed. The applications include (i) surges on grounding electrodes, (ii) lightning surges on overhead power transmission lines (TLs) and towers, (iii) lightning surges on overhead power distribution and telecommunication lines, (iv) lightning electromagnetic environment and surges in power substations, (v) lightning surges on underground power and telecommunication cables, (vi) lightning surges in wind-turbine-generator towers, (vii) lightning surges in photovoltaic (PV) arrays, (viii) lightning surges and electromagnetic environment in buildings, (ix) lightning electromagnetic fields at close and far distances, and others.

An understanding of the physical properties and deleterious effects of lightning is critical to the adequate protection of power and communication lines, aircraft, spacecraft, and other objects and systems. Many aspects of lightning are not yet well understood and are in need of research that often requires the termination of lightning channel on an instrumented object or in the immediate vicinity of various sensors. The probability for a natural lightning to strike a given point on the Earth's surface or an object of interest is very low, even in areas of relatively high lightning activity. Simulation of the lightning channel in a high-voltage laboratory has very limited application, since it does not allow the reproduction of many lightning features important for lightning protection and it does not allow the testing of large distributed systems such as overhead power lines. One promising tool for studying both the direct and the induced effects of lightning is an artificially initiated (or triggered) lightning discharge from a thunderstorm cloud to a designated point on ground. In most respects, the triggered lightning is a controllable analog of natural lightning. The most effective technique for artificial lightning initiation is the so-called rocket-and-wire technique. This technique involves the launching of a small rocket extending a thin wire (either grounded or ungrounded) into the gap between the ground and a charged cloud overhead.

The rocket-and-wire technique has been routinely used since the 1970s to artificially initiate (trigger) lightning from natural thunderclouds for purposes of research and testing. Leader/return stroke sequences in triggered lightning are similar in most (if not all) respects to subsequent leader/return-stroke sequences in natural downward lightning and to all such sequences in object-initiated lightning. The initial processes in triggered lightning are similar to those in object-initiated (upward) lightning and are distinctly different from the first leader/return-stroke sequence in natural downward lightning. The results of triggered-lightning experiments have provided considerable insight into natural lightning processes that would not have been possible from studies of natural lightning due to its random occurrence in space and time. Among such findings are the observation of an UCL in a dart leader/return-stroke sequence, identification of the M-component mode of charge transfer to ground, the observation of a lack of dependence of return-stroke current peak on grounding conditions, discovery of X-rays produced by lightning dart leaders, new insights into the mechanism of cutoff and reestablishment of current in the lightning channel, direct measurements of NOx production by an isolated lightning channel section and the characterization of the electromagnetic environment within tens to hundreds of metres of the lightning channel. Triggered-lightning experiments have contributed significantly to testing the validity of various lightning models and to providing ground-truth data for the US National Lightning Detection Network (NLDN). Triggered lightning has proved to be a very useful tool to study the interaction of lightning with various objects and systems, particularly in view of the fact that simulation of the lightning channel in a high-voltage laboratory does not allow the reproduction of many lightning features important for lightning protection and it does not allow the testing of large distributed systems such as overhead power lines.