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In this paper we analyze the lightning protection system of 48 communication and broadcasting towers situated in similar isokeraunic contours in Sri Lanka. The results show that a direct strike to an antenna structure in a metallic tower is rare irrespective of the presence of an air-termination or a down conductor. However, side flashing or arcing to antenna structures is highly possible once the air-termination and/or down conductor is installed and attempts are made to insulate the system from the tower. The outcome also shows that equipotential bonding of the grounding system, a distributed grounding network including a ring conductor and a suitable system of surge protective devices play a much more vital role in lightning protection of equipment and safety of people than simply achieving a low grounding resistance. However, in the absence of such integrated, distributed and equipotentialized grounding system, a high value of ground resistance sharply increases the possibility of accidents and damage. Considering the observations of the investigations into account we have designed a concrete embedded grounding system for tower sites at problematic locations with respect to ground resistivity. The system performance has been tested by implementing the system at two tower sites and observing the performance for 3 years.

This paper describes the results of a wavelet based noise reduction procedure applied to three lightning electric field signals recorded in Bogota-Colombia, Colombo-Sri Lanka and Toronto-Canada. In general, the evaluated signals were affected by three different noise sources. These are the analog-to-digital converter (ADC), the electronic circuit and the environmental noise.

A comprehensive review has been done on the types of transients that may affect low voltage electrical systems. The paper discusses various characteristics of lightning, switching, nuclear and intentional microwave impulses giving special attention to their impact on equipment and systems. The analysis shows that transients have a wide range of rise time, half peak width, action integral etc. with respect to both source and coupling mechanism. Hence, transient protection technology should be more specific with regard to the capabilities of the protection devices.

Lightning is a major cause of weather related mortality around the world. In the United States, lightning typically kills more people in a year than any other storm disaster except floods. Due to persistent lightning safety efforts and an annual national Lightning Safety Awareness Week campaign, US lightning deaths have decreased to an average of about 50 per year in the past decade. Good statistics about death and injuries around the world are just beginning to be collected. This paper presents an update and overview of the global statistics and trends on lightning fatalities which include the gender, activity, time of event and number of casualties. In addition, meteorological info will also be considered in relation to the lightning activity and fatalities.

This paper discusses the components and techniques of protecting low voltage systems from lightning generated electrical transients and the adequacy of International Standards in addressing the transient protection issues. Our analysis question the suitability of 8/20 µs test current impulse in representing characteristics such as the time derivative or the energy content of lightning currents. The 10/350 µs test current impulse better represents the integrated effect of the energy content of impulse component and long continuing current. A new waveform is required to be specified for testing the ability of protective devices to respond to the fast leading edges of subsequent strokes that may come 100s of millisecond after the preceding stroke. The test voltage waveform 1.2 / 50 µs should also be modified to test the response of protective devices for fast leading edges of induced voltage transients. A surge protective device that is tested for lightning transients may not be able to provide defense against other transients.

Long term performance of several backfill materials, which are freely available as industrial wastes or at a low cost in Sri Lanka, have been investigated by taking the earth resistance of deep driven Galvanized Iron (GI) electrodes over a period of 2–3 years. The best performing material, metal oxide powder (a waste product of steel industry), was tested against several commercially available and traditionally used backfill materials. It was found that these industrial wastes reach the level of performance of commercially available backfill materials after several months. It was also found that the percentage of material erosion of GI due to corrosion in the presence of metal oxide powder is less than 1% after more than two years in contact. Lime and coke breeze also show good performance with respect to corrosion while commercially available natural Bentonite performs the best. Sodium Chloride, a backfill material that is widely used in South Asia, gave highly undesirable outcome; the earth resistance of the relevant electrode fluctuates in a wide range of values and the corrosive effects are unacceptably high. The resistivity and the change of resistivity of each material under dry and wet conditions were measured to find a relation between the earth resistance and the observed parameters. Under dry conditions the resistivity of most of the well performed backfill materials has somewhat higher values, however under wet conditions the resistivity markedly reduces to a low value. This change of resistivity appears to be a characteristic of a good backfill material. However, Sodium Chloride, which possesses such characteristic, should not be used as a backfill material due to a number of drawbacks.

In this paper we show that the scale of damage in buildings with steel reinforcement, due to direct lightning strikes, is insignificantly small compared to the lightning effects on buildings and structures with no such steel reinforcement. The observed small-scale damages are also confined only to the point of strike. A large number of such cases have been observed in Sri Lanka and Malaysia. The fact that almost all these damaged structures, observed in this study, have a steel reinforcement structure, but not verified to be in compliance with the specifications in IEC 62305-3 (2006) for it to act as down conducting system, prompted us to re-think regarding the specifications. Such specifications are difficult to be achieved in practice and also not applicable to buildings that have been already constructed. The recommendations prevents the engineers from using the steel reinforcement as the down conductor in many cases; a fact that leads to either non-installation of LP systems or adopting non-conventional systems which are convenient to be installed. In both cases, a noteworthy advantage that could have obtained by using the steel reinforcement is lost. Use of the steel reinforcement as the down conducting system, which is integrated to a properly designed air-termination system could have prevented even the small-scale damage occurred at the attachment point. Hence, we strongly recommend revising the relevant recommendations in the standards so that a mass public will be benefited. In the absence of such relaxation of the existing guidelines the manufacturers and proponents of nonconventional lightning protection systems enjoy an undue advantage in promoting their technology.