Among the many accidents due to lightning in all parts of the world, Uganda’s incident is widely spoken among experts in the field.
A single lightning flash killed eighteen pupils and a teacher with thirty-eight pupils hospitalised for days on June 28, 2011 at the Runyanya Primary School in the Kiryandongo district, Uganda.
A block of four classrooms was damaged and later abandoned because users considered it haunted as lightning had hit the same building and caused injuries less than a decade before. This was a severe and impactful incident that affected many families and the entire community around the school.
Weather threat
The natural hazard of lightning has become the most frequent weather threat to life most people around the world encounter, including loss of human life and destruction of property.
In September 2011, the Non-Aligned Movement Science and Technology Centre (NAM-S&T Centre) organised an international meeting on lightning, bringing together experts from all continents, all interested in the science of lightning, lightning protection and lightning safety, in Kathmandu, the capital of Nepal in the Himalayas.
I had a privilege to represent Sri Lanka for the event. A lot of discussions were focused on the Runyanya incident. After Uganda’s disaster, scientific community and activists in lightning field accelerated their lightning safety and injury prevention activities leading to extensive brainstorming resulting in organisation of appropriate training courses and awareness campaigns in many countries including Sri Lanka.
An international symposium on strategic interventions to mitigate the hazard of lightning, jointly organised by Centre for Science and Technology of the Non-Aligned and other developing countries (NAM S&T Centre) and African Centre for Lightning and Electromagnetics (ACLE)-Zambia, was held in Lusaka capital of Zambia from August 11 to 13, 2015, with participation of professionals, scientists, engineers from 17 countries including Benin, Cameron, Egypt, India, Iraq, Malawi, Malaysia, Nepal, Nigeria, Pakistan, South Africa, Sri Lanka, Sudan, Uganda, USA, Zambia and Zimbabwe.
I had an opportunity representing Sri Lanka at the event and presented a paper for the symposium. Prof. Chandima Gomes of University of Witwatersrand, Johannesburg, South Africa, eminent Sri Lankan scientist who was one of the main organisers of above two events together with Dr. Shri Ram Sharma of Nepal, Eng. Foster Lubasi from Zambia, Prof. Arun Kulashestra (NAM S & T Centre), Prof. Marry Ann Cooper (USA) and many others. June 28 of every year was named International Lightning Safety Day, to commemorate June 28, 2011 incident in Uganda.
Lightning is the most common weather threat to life that most people in the world encounter – sometimes on a daily basis and often with little knowledge on how to avoid its ravages.
However, lightning, as a random, scattered and unpredictable event remains one of the least attended natural hazards around the globe even though it claims thousands of lives of humans and livestock and damage other important physical property every year.
The lightning’s electrostatic discharge releases up to 1GJ (gigajoule) of energy.
Frequent lightning
Scientists say that the planet witnesses between 50 and 100 lightning episodes per second, even though most of them are not visible to the naked eye. There are over 2,000 thunderstorms in the world at any given moment, with over 100 lightning flashes to ground per second.
The number of annual lightning fatalities has decreased over the last century in developed countries but in least developing and developing nations the picture is totally different.
Lightning causes a number of fatalities in Sri Lanka each year, as well as significant economic losses. At least 30- 50 persons in Sri Lanka are killed by lightning each year. Recent statistics clearly indicates a slight drop of casualties due to lightning (Figure 1).
Seven deaths due to lightning reported for 2021. Three persons died due to lighting at Thanninuippu, in the Mullaitivu District on April 15, 2021. One death due to lighting was reported on the same day at Vellavely (Malayarkaddu).
Another person died in Porativupattu on the same day in the Malayarkaddu Grama Nilaradi division. Another six persons had injuries in Vantharumoolai, Eravur Police area on the same April 15. They were admitted to the Batticaloa Teaching Hospital. It is reported that all who died and injured were engaged in outdoor farming activities.
Seventeen tea estate workers of Daytron Factory at Kotagala, had the impact of lightning while they were weighing their yield in the morning session on May 23 2021.
Spatial distribution (1974-2019) of reported deaths due to lightning is shown in Figure 3. The annual thunder frequency map of Sri Lanka is shown in Figure 4. 2
Source: UNDRR DesInventar Database
It can be highlighted that number of reported causalities due to lightning not only depends on lightning flash density of the area (number of lightning flashes per square kilometer per year), it also depends on several other factors; knowledge on lightning and hazards, reaction to weather advisories, available protection methods and poverty level of the community and their acquisition power of getting protection systems.
Therefore, educating the public on lightning and precautionary methods is the key factor which leads to minimise human and property damages.
Main organisations receive public complaints on lightning damages in Sri Lanka. There are five principal institutions in Sri Lanka where public complaints are received on lightning related issues.
i. Department of Meteorology ii. Disaster Management Centre (DMC)
ii. Telecommunication Regulatory Commission iv. Central Environmental Authority (CEA) and the
Arthur C. Clarke Institute for Modern Technologies, Moratuwa
Police and divisional secretaries also receive public complaints on lightning damages. In general, many people are not aware what precautionary measures to be taken to minimise damages due to lightning and where to approach to get proper information for mitigation.
Human safety
Human safety is the most important factor. Every person should be aware on lightning and safety precautions. The terms lightning “stroke” or “component stroke” apply only to components of cloud-to-ground discharges.
Each stroke involves a downward leader and an upward return stroke and may involve a relatively low level “continuing current” that immediately follows the return stroke.
The majority of lightning discharges, probably three quarters, do not involve ground. These are termed cloud discharges and sometimes are referred as intra-cloud discharges.
Cloud discharges include intra cloud, inter cloud and cloud-to-air discharges (Figure 5). Some 75 percent of discharging are air discharges and only 25 percent are of ground discharges which is the most dangerous for human.
There are negative (90 percent) and positive (10 Percent) cloud to ground discharges and their polarity depends on the prevailing conditions. Cumulonimbus (CB) Cloud is the source of a lightning flash. There are both positive and negative charges within this cloud.
Figure 6 Side flash and step potential
Normally, a single lightning flash has an average of 2-5 individual strokes within a very short duration (200 -300 ms). It has energy range of 100 -1000 mega Jules and has a current range of 25,000 – 200,000 amperes.
There are four ways by which lightning get earthed harming humans and animals and damaging buildings or structures.
(a) Direct lightning, (b) side flash, (c) step potential and (d) touch potential.
Even though the consequences of exposing to direct lightning is so pathetic, human, animal and property damages due to side flash and step potential (Figure 6) are common in Sri Lanka as per previous case studies.
People who are engaging in outdoor activities seek shelter such as under large trees when lightning or thunder storms are occurring. Step voltage also leads huge impact and this can be seen in the incident that occurred in Wakarei, Batticaloa on September 2, 2020 where 27 cows were killed (Figure 7). Human safety and safety of animals are vital.
Lightning protection systems
Lightning protection systems (LPS) are used to protect people as well as property. There are two main LPS namely; standards LPS and non-standards LPS.
Standards LPS is the recommended system by the international community. The standards protection system follows international standards such as IEC 62305 or similar standards or national standards such as SLS 1472 in case of Sri Lanka for building protection and IEC 61643 or SLS 1473 for service line protection.
The International Electro-technical Commission (IEC) is one of the largest international bodies which take care of protection standards. Sri Lanka Standard Institution (SLSI) adopted lightning protection standards from IEC following other countries including UK, India and Australia. Most parts of the world (95 percent) use IEC or adopted versions from IEC standards.
The Integrated LPS system (Figure 8) comprises five main parts; air termination system, down conductor system, earthing system, separation system and lightning equipotential bonding with a surge protective device (SPD) system.
A risk assessment has to be conducted prior to the selection of components and installation. This assessment has to be done in accordance with IEC 62305 or SLS 1472 Standards. An air termination system is used to capture the downward stepped leaders coming from the CB cloud or upward leaders initiated from a very tall structures (height more than 100 m).
Normally copper, aluminium or stainless steel finials (8 mm - 16 mm diameter) finials with 1m or 2m height are used for air termination system.
Some vendors promote different shapes on standards products claiming that 30 m – 70m protection radius.
These are called Early Streamer Emission or ESE type terminals. ESE terminals are not recommended by IEC or SLS standards and many countries such as Malaysia banned such installations. Valid scientific research has been carried out to prove that there is no additional protection provided by these so called ESE terminals.
A down conductor system is used to bring down the huge lightning energy and the earthing system is used to disperse this huge energy to the earth.
Separation distance has to be calculated to keep nearby conductors apart and finally equi-potential bonding and surge protection system will avoid any possible induced current and minimise the induction of different voltage levels.
The number of air terminals, down conductors and earth terminals depend on the dimension of the structure in subject. The design has to be complied with IEC 62305 or SLS 1472 standards and material selected are to be complied with IEC 62561.
Having a proper earthing and bonding system will help reduce 50 percent of the total damages.
Many people are in confusion of a standard system. The number of each sub components are to be decided and calculated by an expert of the field and in accordance with IEC 62305 (or SLS 1472) standards.
A limited people is aware of these standards in the country.
Service lines such as power, telephone, data, antenna and control are needed to be protected with SPDs (Figure 9) in a coordinated manner in accordance with IEC 61643 or SLS 1473 standards.
Nearly 85 percent of property damages due to lightning can be seen on power input or output lines and the balance 15 percent are on data, control, CCTV lines, antenna cables and phone lines.
Policy development for lightning safety
Policy development towards the mitigation of lightning hazards has been initiated not only by developed nations but also by least developed or developing countries.
In Africa, many counties extensively work on lightning safety after international lightning events held in Uganda and Zambia.
Sri Lankan born professor in South Africa Dr. Chandima Gomes was one of the main figures to establish lightning centres in the Africa region. This was after an international conference in Kathmandu, Nepal in 2011.
South Asia Lightning Network
SALNET was established after a similar international event in Tripura, India in 2020.
In Sri Lanka, various attempts were made to establish a lightning centre which will be the apex body to concern on all lightning related activities since 2010 under the National Science and Technology Commission (NASTEC) with the blessings of then Minister Prof. Tissa Vitharana.
Many scientists including Prof. Chandima Gomes, Dr. Rathnasiri of NASTEC, former Director of Meteorology K.R. Abhayasingha, Prof. Dayawansa (Moratuwa University) and Prof. Chandana Jayarathne led the work to draft the first national policy on lightning protection. Representatives from the CEB, Sri Lanka Telecom, TRCSL, university academia, Department of Meteorology (DoM) took part in this endeavour. I was lucky to be a member for drafting the document.
This was raised again in Parliament in 2011 by then MP Vidura Wikramanayake and subsequently a Parliament Select Committee was appointed to study casualties and damages due to lightning.
An expert committee under the leadership of former Director General of Meteorology G. B. Samarasinghe was appointed.
Samarasinghe led the committee in an energetic way and prominent figures, such as Prof. Chandana Jayarathne, Prof. Rohan Lucas, representatives from CEB, SLT, TRCSL, UDA, Health Ministry, DMC, DoM and CEA participated in the task.
This was well supported by then Prime Minister Rathnasiri Wickramanayake and then Minister of Disaster Management Mahinda Amaraweera.
An awareness program was held in Horana under the patronage of former Prime Minister and Vidura Wickramanayke in late 2011.
The Department of Meteorology and DMC published a booklet (Figure 10) and some broachers on lightning safety. Later these were published in the Sinhala and Tamil languages by the DMC with financial support from the UNDP. Conducting of awareness programs on lightning were further accelerated in most parts of the country.
It is so unfortunate that Sri Lanka is unable to establish a Centre for Lightning Safety even with many initial attempts were done but countries, such as Malaysia, India, Nepal, Uganda, Zambia have started their centres and many African and Asian nations are planning to have their centres.
The Arthur C. Clarke Institute for Modern Technology (ACCIMT), Moratuwa has initiated this endeavour two years ago but owing to various factors could not fulfill the goal yet.
Commemoration of International Lightning Safety Day -2021 may help Sri Lankan authorities to open their eyes to implement this idea.
The ACCIMT will host the main event to commemorate the ILSD 2021. Such a centre may help save life of our people by educating, advising and providing protection systems together with all national and international institutions.
(The writer is a Chartered Electrical Engineer/ former Chief Electrical Engineer-Department of Meteorology)