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SINGAPORE – When a power failure first hit the North-South and East-West lines on Oct. 14, SMRT’s first focus was to avoid having to evacuate passengers on stopped trains, CEO Neo Kian Hong said Wednesday (October 28).
Therefore, the operator decided to draw power from an alternative substation at Buona Vista, in an attempt to restore service throughout the affected stations more quickly.
But two of his employees, a supervisor and a staff member, misunderstood the equipment at the substation and thought the power failure at Tuas had isolated itself when it was not.
Failure to isolate the fault before taking power caused a voltage drop in the substation, which feeds the circular line (CCL). This caused a power outage and affected service at the CCL.
The two have been suspended and will need to undergo retraining and recertification before they can resume their duties, Neo told a news conference.
He also said that SMRT took “a lot of safety precautions” when it decided it had to evacuate passengers from stopped trains, to maintain the safety and well-being of passengers on board.
These included suspending the landing of one of the trains near Bukit Batok at 8.44pm due to the risk of rain and lightning.
The train, which was the last to be cleared of passengers, emptied only at 9:43 p.m., two hours and 45 minutes after the failure began.
The Land Transportation Authority (LTA) said Wednesday that passengers had to be untrained from 15 stopped trains, three on the Circle Line and 12 on the North-South and East-West lines.
The download was completed in 20 minutes on the Circle Line, but took more than an hour for those on the North-South and East-West lines.
In a report released Wednesday, the LTA said it had received comments that further updates should be provided on the situation that led to the derailment, “for better awareness and preparedness.”
SMRT will continue to improve its communications during outages and will arrange for its staff to provide more updates to travelers on stopped trains, the LTA said.
He noted that the regular bus services running through the affected stations were immediately released and 120 shuttle buses were mobilized for ferry passengers.
“There were periods of crowded congestion at the bus points at the affected stations initially and then at the stations where the trains were turning,” the LTA said.
Crowds waiting to board buses at Queenstown MRT station, after a power failure caused the suspension of train services, on October 14, 2020. PHOTO: The Straits Times
Investigations later that night found that power cables located about 500 meters from the Tuas Link station along the Tuas West Extension were burned.
There were shorts between three wires in the upper layer of the two-layer power wire network, causing a high fault current that burned the wires.
The section of cable burned that caused the massive disruption on October 14, 2020. PHOTO: LTA
Additionally, a trip coil, a component of a nearby circuit breaker that should have tripped to isolate the fault, was found to have melted. This caused the circuit breaker to fail.
The LTA said repair work on the faulty power cables between the Tuas Link and Tuas West Road stations was completed over two nights, on October 16 and 17.
The faulty firing coil was replaced the night of the incident.
A melted trip coil caused the circuit breaker to fail, causing the outage on October 14, 2020. PHOTO LTA
SMRT checked all trip coils along the West Tuas Extension as a precautionary measure, and found two other trip coils that “exhibited inconsistent performance that could result in a similar failure.”
French firm Alstom, which supplied the power system, is conducting forensic investigations into the faulty firing coils, the LTA said.
The report also revealed that Tuas West Extension had experienced similar cable failures since it began operating in May 2017.
Two cable failures occurred in 2018 and two more occurred this year, in January and June.
All of the failures occurred in the upper layer of the cables, along different sections along the MRT extension line. Train services were unaffected because circuit breakers were tripped to isolate faulty cables, the LTA said.
After the failure in June, Alstom agreed to replace all the power cables in the upper layer with cables that have stronger insulation. The replacement was scheduled to begin this month.
It had also agreed to a 20-year warranty extension for lower layer cables.
Following the October 14 outage, Alstom also agreed to replace all cables in the bottom layer. In total, it will replace some 150 km of cables along the Tuas Oeste Extension by the end of next year, at its own cost.
This article was first published in The times of the strait. Permission is required for reproduction.
