Are you prepared for a lightning strike?
Most of the fires sparked as a result of lightning strikes could be averted if effective lightning protection systems are in place, writes Bob Grieve of Delta Fire.
Lightning strikes are far more common than many facilities managers realise and, with the changes in the global climate and changing weather patterns, they are well and truly on the increase. Australia is at particular risk because, according to a joint NASA (National Aeronautics and Space Administration) and National Space Development Agency of Japan study, approximately 70 percent of lightning occurs on lands in the tropics, where the majority of thunderstorms also occur.
Australia’s Northern Territory is one of the most lightning-prone areas on the planet, but other parts of the country are experiencing an increase in the frequency and severity of lightning storms. Not long ago South Australia witnessed around 50,000 lightning strikes in one night, with the majority occurring in a three-hour period. This started more than 250 fires in the region. Elsewhere around the world lightning has resulted in airports being brought to a standstill, television and radio broadcasts going off-air and commercial operations paralysed, sometimes permanently.
According to the US’s National Weather Service, there are 100 lightning strikes over the earth every second. That equates to more than 8.6 million strikes every single day. Lightning is an explosive, rapid event that releases huge amounts of energy in just a few milliseconds, with an unpredictable path. A single lightning strike releases up to 500 million volts of electricity, with a temperature of around 27,000 degrees.
The impact of a lightning strike can be catastrophic. In reality, there is a little that can be done to protect individuals or the countryside from lightning strikes other than to follow prescribed safety precautions during a thunderstorm. On the other hand, lightning protection can be effective in commercial, industrial and public services sectors.
A factor that every facilities manager needs to consider is the impact of a fire. Globally, most of the fires sparked as a result of lightning strikes could be averted if effective lightning protection systems are in place. The cost of prevention is lower than the cost of the cure.
Achieving effective protection
From a practical standpoint, there are three aspects of lightning protection that the facilities manager should consider, depending on the precise nature of the building and the contents being protected. These can be classified as: lightning protection, grounding/earthing and surge protection.
Traditionally, lightning rods and what is commonly known as early streamer emission (ESE) technology have been used for lightning protection, but, largely for performance reasons, these devices have increasingly been superseded in the past couple of decades by what the industry calls a Charge Transfer System (CTS).
Both lightning rods and ESE technology rely on collecting a lightning strike and inviting it into the facility being protected, whereas the most recently developed technology actually deters the strike from forming within the area being protected and so avoids the risk altogether. This technology includes grounding/earthing and is critical for personal safety, sustainability and uninterrupted operations. Proper grounding serves as the foundation for a complete lightning protection solution, reducing risk and optimising performance. Surge protection safeguards sensitive electronics from lightning that can easily damage or destroy sensitive and often business-critical electronics and IT equipment.
Charge transfer technology and dissipation array
Put in its simplest form, lightning is an electric discharge by which nature equalises the voltage between storm clouds and the earth and, in order for lightning to strike, it must connect the two. The difference in polarity between the bottom of the cloud and the ground is the charge differential. When this charge differential is high, the cloud begins to form downward ‘leaders’ and objects on the ground begin to form upward ‘streamers’.
When a leader connects with a streamer, lightning is given the path it needs to exchange the charge between the earth and the cloud. This reduces the charge differential to upward streamers, which reach up from earth-bound objects when the electrical field is strong enough.
The latest technology based on CTS is called a Dissipation Array System (DAS), which interrupts the formation of these upward streamers through point discharge, a phenomenon where a well-grounded point exchanges ions between the air and the ground.
Point discharge becomes more efficient when the points are connected to a low-impedance grounding system and more ions can be transferred with a greater number of points. DAS technology takes advantage of these principles with an optimal point configuration able to interrupt the formation of upward streamers, thereby preventing direct strikes. Working with grounding and surge suppression to achieve complete protection, a typical system includes: the dissipation array, a low-impedance grounding system using chemically-charged electrodes, a transient voltage surge suppression (TVSS) to protect against transients (short-lived bursts of energy) travelling through data lines and other conductive paths, and modular strike prevention devices to supplement the dissipation array’s area of protection.
To all but specialists in the lightning protection field, this can come across as daunting and complicated, and indeed it is, calling for expert guidance.
Dissipation arrays are available in a range of configurations for almost any structure. These include: a hemisphere array for industrial or commercial structures, including poles, buildings and towers; a parapet array for commercial, healthcare, educational, leisure or industrial flat roof buildings with a parapet around the edge; a conic array for cone-roof and dome-roof petrochemical and flammable storage tanks; and a paragon array for use on transmission and distribution lines. Other designs include arrays for flat roofed buildings, smoke/exhaust stacks and industrial and commercial structures with guy ropes.
Significantly, in terms of maintenance regimes and ongoing operating costs, these solutions require little regular testing, inspection or maintenance other than visual inspection of all moving parts, removal of dirt and debris, lubrication of the bearings and tightening of all mechanical fixings.
Installations can be undertaken at the under-construction stage or retrofitted to existing structures.
Action this day
In many respects, the only safe mindset when it comes to the lightning risk is to consider the question as being not if lightning will strike, but when.
Few people today need convincing that the weather in this country, like elsewhere around the globe, is changing. Every part of Australia has experienced warming in the past 50 years and the CSIRO (Commonwealth Scientific and Industrial Research Organisation), in its State of the Climate report, has confirmed its projections that Australia is going to get hotter and dryer, and storms are going to become more frequent and severe – the precise breeding ground for more destructive lightning.
The debate as to whether these climate changes are cyclical, reversible, naturally occurring or man-made is not the issue here. The issue that facilities managers need to address is that these climate changes are a reality that brings in their wake the prospect of a greater number of more destructive lightning events and the fact that lightning has the very real potential to cause massive disruption to the business and possibly its complete demise.
Bob Grieve is managing director of Delta Fire Australasia Pty Ltd.
Image courtesy of Lightning Eliminators and Consultants Inc.