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Sunday May 24, 2009
By ANDREW SIA
Don’t be fooled by the current hot, dry spell – thunderstorms can still happen. In this final instalment of a two-parter, experts show how best to lightning-proof your property.
WHEN it comes to protecting buildings – and the contents and people inside – from lightning, there are two important steps.
One is external protection, where you put lightning rods on the roof of a building and connect it with thick metal “downward conductors” to the ground. Basically, when lightning strikes these rods, the tremendous burst of electricity is diverted away from the building structure and safely dissipated down to the earth, says Hartono Zainal Abidin, an electrical engineer and lightning expert.
This is akin to encasing the building in a metal cage (called a Faraday cage in physics). While lightning can move along the outside, it can’t penetrate into the cage.
Second, is internal protection. Even though our home may be protected externally by a Faraday cage, any wires running into our living or bedrooms are, in effect, “holes” in that cage, says Jimmy Lim, managing director of Tokai Engineering, one of the leading lightning protection companies in Malaysia.
When lightning strikes power or telephone lines outside, it can travel indoors as a “power surge” to burn out our electrical equipment (or give us nasty shocks).
Sometimes, lightning may strike the ground nearby our home and the power surge can travel along the ground and then into our homes through the “earthing” wires (which are found in every house).
The way to avert these situations, Lim asserts, is to have good lightning “surge arrestors”.
These are called Franklin rods, after Benjamin Franklin, the American politician and scientist who invented them some two centuries ago.
Each intermediate terrace house would typically need one rod (or two to be extra safe) with a pair of downward conductors running down externally.
But exactly where do you place the rods? This is an area where Hartono and his wife, Robiah Ibrahim, (also electrical engineer) have made an important contribution to the global lightning protection standard.
And they did it the hard way. On rain-lashed thunderstorm nights, this couple, both aged 52, used to brave the elements, and go out in their car to observe lightning.
“In the early 1990s, we used to park our car in the hills around KL or the rooftop of some shopping centre where we could see lots of sky. We were observing Malaysian lightning and comparing it with what we read in the textbooks.”
In fact they met while monitoring lightning damage to various equipment when they were both working for Telekom Malaysia, and then got married in 1980.
They have also gone round photographing lots of buildings which have been struck by thunderbolts.
“There are so many lightning-damaged buildings in Malaysia that we could collate the data and look for patterns. We found that 80% of strikes are at the corners of buildings and we wrote this into our research paper in 1995,” says Hartono.
That is why they can now advise the public that Franklin rods should be placed at all the roof corners of a corner terrace house (or semi-detached houses) and also on protruding structures such as large bay windows.
“Such corners are also the wrong place to put Astro dishes,” he smiles. “That’s just like trying to increase the business for new Astro sets!”
He has also found that bungalows have the highest risk for lightning strikes, followed by semi-dees (and corner terrrace houses), while intermediate terrace house units are least likely to be hit.
Hartono points out that lightning will hit anything it likes, not necessarily the highest point.
“For instance, see that condo over there,” he tells this writer while we are on the roof of the Menara Star building. “It has a pyramid-shaped roof but lightning has hit the lower corners of the building, not the pyramid peak.”
Hartono’s field research was recognised by an Australian lightning expert, Emeritus Professor Mat Darveniza from the University of Queensland, who then submitted it to the International Electrotechnical Commission (IEC) to become part of a new global standard (the IEC 62305) on lightning-related engineering safety in 2006.
“Before this, the placement of lightning rods depended on the knowledge and intuition of the design engineer,” explains Hartono. “This resulted in many buildings being struck and damaged by lightning even though they were installed with lightning rods.
However, while Franklin rods are a proven technology, there are architects who don’t like to have such “unsightly” rods on a building’s roof and instead install just one or two ESE (early streamer emission) lightning rods which (falsely) claim to be cover a large area.
If aesthetics are an issue, Hartono says that Franklin rods can be modified into any shape desired.
“They don’t have to be straight rods sticking out. They can be flat metallic pieces which blend into a building’s facade,” he clarifies. “Or the rods can be bent. In fact, some Chinese temples have them curved around dragons carvings on their roof tops.”
For an ordinary link house, it should cost about RM5,000 to RM10,000 to set it all up, he estimates.
“This includes the cost of grounding. If you have laterite soil that conducts electricity quite well, you may only need two earth rods, one on either (opposing) side of your house. But if your house is built on sandy former mining land, it will not dissipate lightning so well and you may need extra earth rods.”
Copper is the metal of choice (as a conductor of electricity) for Franklin rods but aluminium is almost as good and much cheaper says Lim. Each rod will protect an area in a 45-degree zone downwards from the tip.
For buildings below 20m in height, there should be one Franklin rod for every 20m of building length. If the building is higher than 20m, there should be one Franklin rod for every 10m.
Regarding the May 11 incident when lightning struck a fishing boat off Kuala Terengganu (injuring 10 people), Hartono also recalls three fishermen being killed by lightning on kelongs (wooden platforms built out at sea to catch or farm fish) in 2006.
He says a boat (and kelongs too) can have their own lightning protection systems.
“You need Franklin rods on the pilot’s cabin and a metallic wire stretched from front to back, all connected to the ‘earthing’ which is done with a metal plate stuck to the boat below the water line. Such systems are used on luxury yachts.”
This is the second component to lightning-proof a building. One of Lim’s first projects after starting Tokai Engineering in 1993 was a resort in Pulau Tioman.
“There were many spread-out chalets with phones connected to the central office. But during every monsoon, the PABX phone system would be knocked out,” he recalls.
“Other engineers just recommended putting in more (external) lightning and earthing rods. But we recommended (internal) surge arrestors to the phone system itself. During the next monsoon, their phones were fine.”
Hartono recalls that when he and his wife were working with Telekom Malaysia in the 1980s and 90s, there were lots of lightning-related problems.
“Mobile phone operators were also having problems. All this happened as computers and electronics were being introduced to telecommunications globally then. Even the developed countries had not fully studied such lightning problems. It was only in the mid-1990s that we overcame them.”
He was called in when lightning interrupted services on the Putra LRT trains before the 1998 Commonwealth Games and also when lightning disrupted operations at the Kerteh petro-chemical complex. In all these cases, proper surge protection and grounding was the way to go.
He notes that this also applies in the manufacturing sector.
“Nowadays they all use computer systems with sensors to control processes in far-flung parts of the factory. The architecture is like a telephone system because it’s all linked back to a central control room.”
As for the Putrajaya Hospital case, where a lightning strike on April 11 caused a fire on the third rather than the (top) fifth floor, Lim thinks there are two scenarios:
Firstly, perhaps the downward conductors were not adequate and so the lightning could not be dispersed to the ground completely.
“Part of that excess power has to go somewhere and that’s when side flashes occur. It is possible there was no fire near the roof because of the rain, but inside the building on the third floor, sparks can set off fires.”
Another scenario is that lightning surged through the power or telephone lines and literally burnt equipment on the third floor.
As for our humble homes, Lim cautions that if a house has external electrical points, for instance at an auto-gate or a gate lamp, lightning can strike them and then surge into your home.
His company deals in high-end heavy duty surge protectors which have been used by various petroleum and telecommunications companies, as well as the Prime Minister’s office.
“Usually we will install surge protection at the power supply and also for sensitive equipment like the computer, TV and hi-fi system. Equipment like fridges are more hardy and don’t need special protection.”
Asked about the much cheaper products in the supermarkets, Lim replies: “Their reliability is questionable.”
On his part, Hartonowarns that, like many other products, there are fakes in the market and recommends getting surge protectors directly from reliable suppliers rather than from electrical contractors.
Beware of fraud rods
Suriving a strike
Bolts of disaster
Land of lightning
Shielding public spaces
The weatherman tells why
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