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| Sunday, 18 May 2003 |
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Accidents caused by lightning on the increase by NEOMI KODIKARA With the inter-monsoon season now in full swing, evening thunder showers, accompanied by lightning are all too common occurrences. But awesome as the displays are, lightning is also fatal and if the experts are to be believed, incidents of lightning-related accidents are on the increase. In fact the experts claim that the increase to be 'drastic' and say that lightning activities over Sri Lanka have intensified in the past five years. This is confirmed by Dr. Chandima Gomes, Charted Physicist (UK), Consulting Engineer in Lightning Protection and Senior Lecturer in Physics, University of Colombo who says that human casualties as well as lightning-caused property damages due to lightning are evident to be on the rise. "This may be due to widespread media coverage or an increase in the use of electronic appliances or higher number of towers coming up," he says. Whatever the reason, every year lightning kills more than 50 people and causes over Rs. 100 million worth damage to equipment and property in Sri Lanka. This year too about 20 people have been struck by lightning and many incidents of building damages have been recorded. However, Dr. Gomes points out that these incidents occurred in the first lightning season of the year and the most intensive stage is yet to come. Giving credence to the theory that the erection of communication towers may be causing an increase in lightning intensity, residents living in close proximity to communication, broadcasting and telecasting have been experiencing concern about their safety the past few years. A large number of towers were erected in urban areas in Sri Lanka, especially for the purpose of cellular communication, during the past decade. People living in areas like Horana, Padukka, Matugama, Kalutara, Avissawella and Negombo have complained about lightning-related problems they have been encountering since the erection of towers. Many complain that the academics and professionals in lightning protection pay no attention to their grievances, leaving them at the mercy of the tower owners. Some complain of property damages, injuries and deaths caused by lightning in the region, after the erection of the tower. Some also claim that the adverse effects of lightning have increased drastically with the installation of lightning protection systems in the tower. Many say they have noticed that the lightning protection system throws the so-called ball of lightning out of the tower so that it could strike a person or objects in the vicinity. Dr. Gomes says that close investigation of the sales promotions of some lightning protection vendors had revealed that the residents allegation is not baseless. Aggravating the situation is the fact that no proper research or at least statistical survey on lightning has been conducted so far. Geographically Sri Lanka is located at the second highest density side and the occurrences is much higher than in the other countries. Incidents of lightning in the island is second only to Central Africa. Around 60 occurrences of ball lightning, which is a rare phenomenon, had been reported during past 4-5 years in the country. This, according to experts is extremely high as in most countries ball lightning occurs only once in four to five years.Lightning occurs during the inter-monsoonal season from April to June and from October to November. During these periods convective clouds (culonimum) develops over most parts of the island, particulary during the afternoon or evening. Lightning occurs usually between 3 p.m. to 6 p.m. with intense lightning at around 4 p.m. The increase in lightning intensity has created a lucrative market for lightning repellers. But due to the non-existence of lightning standards in the country, anyone can import and sell any lightning repellers. Disturbingly into more than 50 per cent of the lightning protecting systems imported in to the country are non-compliable with the International Standards (IEC), British Standards (BS), Australian National Standards or even American Standards.Dr. Gomes stressing the need for a Lightning Forum, says that the lack of communication between the engineers and scientists is one of the main obstacles to establishing lightning standards. "Here, there is a vast gap between engineers and scientists. Scientists know the theories of latest developments but they lack practical application and it is the same with the engineers. So we need to bridge this gap," he says pointing out that if the Government could initially fund and establish a Forum, it could be run with funding assistance from many agencies.' The absence of surveys and standards can often lead to 'old wives tales' in safeguarding themselves against devastation. Lightning ignites fires that may bring entire building or houses down to ashes. At a lower degree of damage, lightning currents may destroy electronic and communication equipment beyond repair. The lightning current reaches a maximum density of about 30,000 amperes an average, but current in the range of 300,000 amperes are also reported. The lightning current heats its path to a temperature of about 40,000 celsius which is eight times higher than the temperature on the surface of the sun, which is about 5000 celsius. So how does lightning occur? In the first stage of a lightning strike, a channel of charge flows towards the ground from the cloud. When this channel is above 50-100 metres or above, earthbound objects in the vicinity (eg. humans, trees, buildings, animals) start sending upward channels of opposite charge to meet the downward channel. Subsequently a powerful current will flow through the objects which send the upward channel, striking whatever or whoever is in the way. The tallest protrusion in a certain landscape may be the unfortunate object that sends the first upward channel that meets the downward stream of channel from the cloud.Maximum damage is caused when a building attracts a downward lightning leader (direct strike) or attracts a part of a lightning flash that hits another structure in close proximity (side flash). This mode causes damages at a very rapid rate so that once a building is struck by lightning it is very unlikely that the damage to equipment, or human injuries can be prevented. The second mode of getting lightning current into an installation is through the service lines such as power, communication and cable TV. Once lightning strikes a service line, fractions of the lightning current enter through the service line and may destroy all the equipment that is plugged into the system. The lightning current may also injure the user of equipment connected to the service lines. This causes less damage than a direct strike, but lines are subjected to lightning strikes much more frequently than buildings themselves. Precautionary measures to reduce lightning hazards If you can hear thunder you are close enough to be struck by lightning. Avoid being outdoors during this period. Avoid being under or near tall trees, in or on water, on or near hilltops and riding bicycles or open vehicles. Unplug and refrain from using any electrical appliances; disconnect the antenna cables from the television set and put them completely outside the house. Use the telephone only in an emergency. Never repair electrical networks (house wiring) during thunderstorms. Do not take a bath or shower at the time of lightning. Turn off air conditioners to avoid overloading the compressors. If you are caught outdoors, find a low spot that is not subject to flooding and away from tall trees, wire fences and poles. If you happen to be in a forest area, never take shelter under tall trees. If you feel your skin tingle and your hairs stand on end, squat down low to the ground on the balls of your feet. Place your hands on your knees with your head between them. Then you make yourself the smallest target possible and minimise your contact with the ground. If you are bathing or swimming get to land soon and find shelter immediately. If your house is in a vicinity prone to lightning hazards frequently, lie stretched on a bed inside the house, remove all metal structures and tall trees near the house, and install an effective earthing system. Lightning often strikes outside of heavy rain and may occur as far as 15 Km away from any rainfall. If the thunder is heard after 15 seconds, lightning activity is imminent within five Kilometres. |
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