Train stalled? It may be balloon's fault

Priscilla Goy, The Straits Times AsiaOne 16 Oct 15;

Did you know that your shiny, metallic helium balloons could disrupt MRT train services?

It is no laughing matter if your Minion or Minnie Mouse balloon flies up and away, and posters have recently been put up at stations on the North East Line (NEL) to remind commuters to hold on tightly to their balloons.

In the poster, train operator SBS Transit explains: "If (the balloons) get caught in the overhead power lines, they can cause a power trip and bring train services to a halt."

SBS Transit told The Straits Times that it decided to put up the posters two months ago after a train disruption happened on April 6 last year.
In that incident, train services on the NEL were disrupted for close to an hour in both directions between Farrer Park and Boon Keng stations due to a power trip.

Investigations by the Land Transport Authority showed that a passenger had accidentally released an aluminium foil helium balloon, which slipped into the tunnel at Boon Keng Station when the platform screen doors were opened.

The balloon then came into contact with an electrical insulator of the overhead catenary system - the power supply system installed on the ceiling of the train tunnel - and caused an electrical fault.

Said Professor Liew Ah Choy from the National University of Singapore's Electrical and Computer Engineering Department: "The aluminium foil is an electrical conductor and when it comes into contact with the live overhead wires a short circuit occurs. This would trigger the circuit breakers to trip, to prevent further damage to the electrical equipment."

Meanwhile, SBS Transit's senior vice-president of corporate communications, Ms Tammy Tan, told The Straits Times: "There has not been a recurrence of last year's April incident, but prevention is better than cure and the posters have been put up as a precautionary measure."

The 16-station NEL is the only MRT line here powered by overhead catenary systems instead of a power-supplying rail on the ground, so the posters are put up only in NEL stations.

But the posters can be hard to spot, as several stations have just two or three posters put up along the platform. A few commuters who frequent the Clarke Quay Station told The Straits Times they saw the posters only in recent weeks.

While incidents of balloons causing power trips are rare here, they happen more often in cities like Hong Kong, where there are signs telling people not to take balloons into train stations.

According to a Hong Kong magazine, the ban was started in 1996, when a Minnie Mouse balloon floated into a tunnel at rush hour. The resulting short circuit halted all trains between Admiralty and Quarry Bay - both interchange stations - for 1½ hours and affected 100,000 commuters.

How do balloons cause MRT train faults?
Teo Kai Xiang Yahoo Newsroom 16 Oct 15;

“Hold them Tightly — Do you know that BALLOONS, especially the metallic shiny ones, can STOP a train?” is a warning that is appearing in some MRT stations along the North East Line (NEL).

Posters warning commuters about the dangers of releasing balloons inside MRT stations began appearing in MRT Stations on the NEL two months ago, and commuters reacted with disbelief online.

In a discussion thread on HardwareZone, netizens questioned whether balloons really had such destructive potential.

According to the Land Transport Authority, last year’s train disruption on 6 April was traced to a balloon which had slipped into the tunnel at Boon Keng station, reported the Straits Times. When the balloon came into contact with the electrical insulator of the overhead power supply system on the ceiling of the tunnel, it triggered an electrical fault.

“But how can the balloons enter the tunnel?” asked user Morgan23 on the forum thread. Another user questioned how frequently balloons caused such faults. “As if there are many balloons?” wrote user stillgottheblues.

Yahoo Singapore has reached out to SBS Transit to find out how it is possible for balloons to enter the MRT tunnel, and the number of train faults caused by balloons since the disruption on 6 April last year.

The warning posters only appear along the stations on the NEL because only it is the only line using the overhead power supply system.

Many in the same discussion thread said they had not seen the posters at all. Some netizens questioned why balloons were singled out for this warning, when other objects such as earrings have also been the cause of door faults which can slow down an MRT.