SINGAPORE: A breakdown of insulation of a power cable and an attempt to restore power to two MRT lines without "first isolating the fault" led to disruption in train services on Wednesday night (Oct 14), SMRT said on Thursday.
The transport operator apologised on Thursday for the disruption during peak-hour traffic on Wednesday evening.
The disruption affected train services from Woodlands to Jurong East on the North-South Line, Queenstown to Gul Circle on the East-West Line, and HarbourFront to Serangoon on the Circle Line.
Some commuters had to walk on tracks to make their way back to the station, while bus stops were packed with commuters looking for alternative ways to continue their journey.
Train service on the Circle Line resumed at about 8.40pm, while services on the North-South and East-West lines resumed at about 10.35pm.
The disruption started with a breakdown of insulation of a power cable between Tuas Link and Tuas West Road stations, SMRT said, citing its preliminary findings.
A circuit breaker at Tuas West Road station "should have kicked in" to isolate the fault, but it did not, said SMRT in its media release. This caused the North-South and East-West lines power system to trip.
To restore power to these lines, there was an attempt to draw power from the Buona Vista Intake substation.
But this was done "without first isolating the fault", resulting in a power supply disruption to the Circle Line, as the Buona Vista Intake substation also serves the Circle Line.
"The insulation fault has been identified and isolated and the faulty component of the circuit breaker has been replaced," SMRT said, adding that train services were running normally on Thursday.