A FAULTY back-up power supply system in the operations control centre disrupted services on the Downtown Line for 35 minutes on Friday morning.
The fault occurred at about 9.35am, disrupting train services in both directions at all six stations on the 4.3km line, which opened last December.
SBS Transit said there was a defect in the uninterruptible power supply system, which provides back-up power for the centre when the main electrical supply is down.
This affected the centre's ability to control and monitor train operations, it said.
The operator opted to hold back all trains at the stations' platforms as a safety precaution.
SBS Transit and Land Transport Authority (LTA) engineers responded to the fault, and full service resumed at about 10.10am.
The disruption affected about 1,700 commuters. SBS Transit and the LTA are investigating the cause of the failure.
The operator deployed 14 shuttle buses to ferry affected commuters for free during the disruption. They were also permitted to take free rides on buses passing by all six affected stations.
Ninety SBS Transit "goodwill ambassadors" assisted commuters at affected stations.
The new Downtown Line Stage 1 has suffered several faults since its opening.
A signalling fault delayed service for nearly two hours on Feb 7, while a disruption on Dec 28 last year was attributed to a young girl who could have activated a detrainment switch that cut off power.
The line also encountered a train fault on its opening day.
National University of Singapore transport researcher Lee Der Horng noted that a new system does not necessarily translate into a problem-free one.
"It could be that the unit is a lemon," he said. "If only that unit is faulty, it has little relevance to the overall system design and engineering reliability."
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