Singapore - Lightning strike caused major disruptions to SMRT

[Coordinator]

April 23 rail incident among "more major" disruptions: SMRT
By Neo Chai Chin | Posted: 04 May 2010 2338 hrs


SINGAPORE: The lightning strike on the Bukit Panjang light rail
transit network nearly two weeks ago, was one of several that have
disrupted rail services in the last decade. And it was one of the more
major incidents, damaging the power equipment of one of the trains,
according to operator SMRT.

But lightning strikes don't always spell bad news for commuters,
according to a lightning protection expert.

This is because of the lightning protection devices in place, which
could reduce potential damage by 90 per cent, said Professor Liew Ah
Choy, an electrical and computer engineering don at the National
University of Singapore.

This means that in 10 instances of a lightning strike, only one
incident would cause service disruption.

The devices include lightning protection tape on the rails and surge
arresters to limit potential damage to the rail network's electronic
systems.

The tape safeguards against direct strikes on the rail. "When the
lightning current gets injected into the lightning protection tape,
there will be a large voltage rise and a lot of current flowing, and a
very large magnetic field generated," explained Professor Liew.

The "very high" voltages induced by lightning vary from several
kilovolts to 100 kilovolts, and can cause power failure.

But in some instances, the surge arresters are able to limit the
voltage values so that no damage is caused, said Prof Liew.

While no lightning protection safeguard is fail-proof, Singapore has
done a good job of minimising the frequency of disruption, he said.

Since the Bukit Panjang LRT system began operations in 1999, there
have been three instance of delays caused by power surges, said Mr Tay
Tien Seng, SMRT's light rail operations director.

In the April 23 incident, engineers managed to get one of the trains
functioning again, while a rescue train was sent to push the second
defective train to the nearest station.

About 100 passengers were on the two trains, but none was in danger at
any time during the incident, said SMRT in a statement after the
incident.

However, a 60-year-old Bukit Panjang resident, Mr Chen, who was
affected by the disruption, said station staff could have done more to
prevent would-be passengers from scanning their cards and heading up
to the train platform.

Had there not been a thunderstorm, passengers could have got off the
train and walked on the track to the nearest station, said Mr Tay.

They would have walked a safe middle passage flanked by the train
tracks.

Meanwhile, last month's disruption also threw up another interesting
statistic.

Three other lightning-induced train disruptions reported in the media
since 2001 have also occurred in April - one of the months with the
most thunder days alongside May and November/December, according to
statistics from the National Environment Agency. - CNA/vm