Science · Uncategorized

纸的力量 (Strength of Paper)

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Electricity · Environment · Science · Uncategorized

Practical Electricity in Real Life: Intuition vs Science

Read an interesting article today, parking it here for future reference

http://www.straitstimes.com/singapore/housing/lightning-protection-or-hazard

Talks are under way to revise a building code that regulates lightning protection to address safety in the growing number of roof terraces in housing developments.

Residents in at least one condominium development have avoided using their own private roof terraces since July last year over such concerns.

The lightning protection system at mixed-use development Bedok Residences has the lightning rods connected to the metal rails and facades of the rooftop units.

“I don’t even want my domestic helper to clean the area since lightning can strike at any time,” said resident Dennis Lim, who is in his 50s.

As a result, he and other residents have avoided using their barbecue pits and jacuzzis on their terraces.

Another resident, Ms Tay Min Li, in her 20s, said: “If I touch the metal rail and the lightning strikes elsewhere, won’t I be electrocuted?”

Some owners of penthouse units at condominium Bedok Residences have avoided using the barbecue pits and jacuzzis on their private roof terraces when they saw that the lightning rods connect to the metal rails and facades of the units (above right). H
Some owners of penthouse units at condominium Bedok Residences have avoided using the barbecue pits and jacuzzis on their private roof terraces when they saw that the lightning rods connect to the metal rails and facades of the units (above). However, while it seems counter-intuitive, checks reveal that the roof terrace and accompanying balustrades are safe. ST PHOTOS: ALPHONSUS CHERN

While it may seem counter-intuitive, checks have revealed that the roof terraces and accompanying balustrades are in fact safe.

Experts explained that the lighting protection system reduces the risk of injury thanks to the concept of “equipotential bonding”, in which metal parts on the roof are earthed if they are connected to the ground.

When lightning strikes, its electrical current will follow the path of least resistance to the ground through the metal instead of the human body, said Mr Ken Jung, vice-president of the Singapore Electrical Contractors and Licensed Electrical Workers Association.

Both the Building and Construction Authority (BCA) and developer CapitaLand Singapore confirmed that Bedok Residences’ lightning protection system was certified by a professional electrical engineer for its temporary occupation permit.

Professor Liew Ah Choy, who chairs the technical committee of the current lightning protection code, however, noted that given the increasing trend towards having accessible or private roof areas, the lighting protection code for roof terraces is being reviewed.

In its current state, the lightning protection code – Singapore Standards 555 (SS 555), which was introduced in 2010 – does not refer specifically to roof terraces, noted the National University of Singapore adjunct professor.

A NEED TO ENLIGHTEN

Most people have a limited understanding as to how lightning works, so it is important to educate people on how a building’s lightning protection works.

MR KEN JUNG, vice-president of the Singapore Electrical Contractors and Licensed Electrical Workers Association.

Similar systems can be seen at developments with publicly accessible roofs, such as Marina Bay Sands and the Pinnacle @ Dawson.

The Straits Times understands that one of the ideas mooted in the new lightning protection code involves parapet capping, where the entire edge of the roof is encased in metal.

Another possibility is a trellis, which functions as an enlarged lightning rod.

However, these fully metallic structures may actually look more alarming to some residents, said Mr Jung.

“Most people have a limited understanding as to how lightning works, so it is important to educate people on how a building’s lightning protection works,” he said.

The BCA spokesman said that as a precaution, residents who own units with roof terraces should stay indoors during inclement weather.