Commuters are likely to continue facing shorter MRT operating hours in the run-up to weekends over the coming year as works to renew the North-South, East-West Lines' (NSEWL) power supply start this month.
The Land Transport Authority (LTA) said yesterday that the latest asset-renewal programme will be completed in the early 2020s - by 2024 at the latest.
The power supply renewal works "will make use of additional engineering hours from the scheduled early closures and late openings over the coming months", it said.
Commuters have had to bear with these for about a year now.
"Enhancement works will also be carried out concurrently to improve the system's resilience to enable better prediction of faults, thereby shortening recovery timeframes during a disruption," a spokesman added.
About 1,300km of power cables, 250km of fibre optic cables along the two lines' tracks, 206 power transformers, 172 switchboards and equipment in 171 substations will be replaced.
A condition-monitoring system will be installed on the two lines, the oldest in Singapore's MRT network.
The system will monitor the health of power supply equipment, and real-time information such as voltage and temperature will be transmitted to operator SMRT's operations control centre, "so that irregularities can be picked up early, enabling SMRT to carry out further investigations and rectification works where necessary".
The LTA added that the current 64P touch voltage protection system will also be replaced with voltage-limiting devices (VLD).
Traditionally, the 64P system halts train operations when the touch voltage of the railway is elevated, triggering safety mechanisms to kick in. This was what triggered the severe two-line breakdown in July 2015 which left about half a million commuters stranded, many until midnight.
"With the installation of the new VLD, the touch voltage will be mitigated without affecting rail operations," the LTA said. "The NSEWL's high voltage network will also be reconfigured to ensure that no single point of failure will disrupt the entire rail network."
Disconnector switches will also be installed to compartmentalise the rail network power supply.
This means that in the event of a power substation failure, the fault will be localised, minimising disruption to other stretches of the same train line.
To minimise the impact of these major renewal works on commuter service, back-up standby generators and mobile substations will be deployed. In addition, critical migration works, such as putting new switchgears into service, will be scheduled to take place on weekends.
