• The Land Transport Authority released its report on the latest major train breakdown that affected about 123,000 commuters
• There were four cable faults on Tuas West Extension before the latest incident but train services were not disrupted as circuit breakers kicked in
• In the latest incident, a circuit breaker malfunctioned, leading to the breakdown on the North-South, East-West Lines
• The Circle Line was, however, affected due to human error; two SMRT staff suspended

SINGAPORE — French train manufacturer Alstom will replace 150km of power cables along the Tuas West Extension following a massive train disruption on Oct 14 which affected more than 120,000 passengers and train service on some lines for more than three hours.

The Land Transport Authority (LTA), in a briefing on Wednesday (Oct 28) to present its findings on the disruption that affected 36 stations across the North-South, East-West (NSEWL) and Circle lines, said that the power cables were the cause of four other incidents since 2018.

The replacement cables will have a more resistant internal structure with a thicker metallic screen.

Alstom will bear the cost for the replacement.

The LTA added that as an added precaution, Alstom will also replace all 113 trip coils, a component in circuit breakers, along the same stretch by the end of this year.

To complete the change out, train service will end earlier along some stretches of the MRT system from next month.

Train service will also end earlier or start later on weekends, or there may be full Sunday closures for limited periods next year, said LTA.

WHAT HAPPENED

The LTA confirmed on Wednesday that the disruption, which resulted in 15 trains with more than 6,700 passengers having to be detrained, was sparked by a section of 22kV power cables that had “burnt through”.

It said that there were four other occasions where there was a fault with the power cables along the Tuas West Extension, but train service was not affected as circuit breakers managed to kick in to isolate the affected electrical zones.

On Oct 14, however, a circuit breaker that was close to the fault also malfunctioned.

LTA said that as a result, a secondary protection mechanism kicked in and isolated a larger electrical sector as a precaution.

This caused the power supply from the Tuas Depot Intake substation to be cut off, disrupting the power supply to the affected sector from Woodlands to Jurong East and Queenstown to Gul Circle on the NSEWL.

TODAY understands that these power cables are also used on the Downtown Line but this line is underground, so cables are not exposed to the elements of weather.

On Wednesday, senior vice president for Asia Pacific at Alstom, Ms Fang Ling, said: “Alstom is deeply sorry for the inconvenience caused to Singapore commuters during the disruption of train service on the East-West, North-South and Circle lines.

“In line with our absolute commitment to operational safety, and as a precautionary measure, we are replacing all the power cables with the highest specifications and the circuit breaker trip coils in the safest and the quickest way possible.”

CIRCLE LINE WAS DOWN DUE TO HUMAN ERROR

While the fault started with physical components, human error by two SMRT staff members led to the disruption having a knock-on effect on the Circle Line. 

They misread a graphic display and thought that the cable fault had already been isolated within its electrical zone and attempted to draw power from a substation at Buona Vista, which also supplies power to the Circle Line.

In explaining the mistake, LTA said: “As the faulty cable at Tuas West Road Station had yet to be isolated, this led to a voltage dip at Buona Vista Intake, which activated the safety mechanism that tripped to protect the Circle Line’s power system. This, in turn, affected train services along parts of the Circle Line.”

SMRT group chief executive officer Neo Kian Hong told reporters at the press conference that the staff members responsible were suspended from their duties and were required to undergo retraining and recertification before they can resume work.

He also said that SMRT’s focus that night was to avoid detraining passengers.

As a result, commuters were escorted off trains only 40 minutes into the disruption when SMRT assessed that the power supply could not be restored quickly.

Detrainment on the Circle Line was completed in 20 minutes, at 8.17pm that night, but it was dragged out for the NSEWL due to inclement weather and lightning risk.

While passengers on 11 of the 12 stalled trains were able to make their way to the nearest station by 8.42pm, passengers on one train were only able to do so at 9.43pm.

NSEWL services were progressively restored at 10.34pm that night. Circle Line services were progressively restored at about 8.45pm.