MRT equipment supplier Alstom intends to conduct a complete replacement of all power cables along the Tuas West Extension — the cause of the disruption on Oct. 14.

Minister for Transport Ong Ye Kung said in his response to parliamentary questions on Nov. 3 that the replacement work will be completed progressively by the end of next year.

"At the right time, LTA will schedule early closures and late openings on weekends or full Sunday closures for limited periods in 2021 next year, to facilitate the cable replacement works," said Ong.

Standard Operating Procedures

Member of Parliament (MP) Joan Pereira asked if there are sufficient plans and preparedness exercises to ensure that the relevant teams know what to do in the event of a power failure.

Ong said: "There are, in fact, many sets of SOPs to cater to different scenarios. But one thing we have learned over the years is that every disruption is different and unique."

Ong added that the engineers have to exercise their own judgement to make quick decisions when there are emergencies.

"I have not been in their shoes and cannot imagine the challenges they are facing. But under the pressure of time and circumstances, the personnel involved I believe made an honest mistake.

I have no doubt this has been a major lesson for them, they wish they had decided differently, and they have much learning to share with their colleagues, so that such a mistake will not happen again," said Ong.

When to 'detrain'

Saktiandi Supaat asked in a supplementary question whether the SOP dictated how long before a decision is made to evacuate commuters off the train, citing concerns of ventilation and anxiety from being stuck.

Ong replied that when such disruptions happen, the battery on the train will be activated to power a fan to provide some light ventilation. The battery will typically last for an hour, during which a decision has to be made about whether to detrain or not.

However, Ong said that the decision to detrain is not made lightly because they have to take into consideration the risk involved.

He said that the risk of tripping and guaranteeing that the 750 volt DC third rail on the tracks was disabled are among some of the considerations they take when making the decision.

"That night there was inclement weather, and then there's lightning risk. And once we felt there's lightning risk, we stop. Never put passengers lives in danger," Ong added.

"But typically, after half an hour, a decision should be made, whether to do detrainment."

Pritam Singh, leader of the Workers' Party asked if there was a consistent reason for the earlier episodes of cable failure, and if so whether pre-emptive measures could be taken.

Ong replied there were four failures, two when the system was commissioned in 2018, no failures in 2019, and two failures in 2020. He said the reasons for the failure has not yet been established, which is why forensic investigation is needed.

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Top image adapted from screenshot from CNA.