NEL, Sengkang-Punggol LRT disruption: LTA, SBS Transit working to avoid repeat of rare 'double fault' scenario
Engineers will test around 28km of cables along the Sengkang-Punggol LRT network to assess their condition by Aug 23, say LTA and SBS Transit.
A notice at Farrer Park MRT station after a power fault led to a disruption of train services on the North East Line on Aug 12, 2025 (left) and bus bridging services provided during a disruption on the Sengkang-Punggol LRT on Aug 15, 2025 (Photo: CNA/Koh Wan Ting, SBS Transit)
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SINGAPORE: The Land Transport Authority (LTA) and SBS Transit are working on eliminating a recurrence of the "double fault" scenario that affected the North-East Line (NEL) and Sengkang-Punggol LRT.
Such a scenario is "rare", LTA and SBS Transit said in a joint statement on Saturday (Aug 16).
On Tuesday, the power fault incidents disrupted services on the NEL for about three hours and Sengkang-Punggol LRT for about five hours. Repairs were completed on Saturday.
Services on the Sengkang-Punggol LRT were again disrupted on Friday for about four hours.
LTA and SBS Transit are still investigating the cause of the cable fault, and their engineers are testing the cables along the entire Sengkang-Punggol LRT network to assess their condition. The tests are set to be completed by Aug 23.
THE POWER FAULTS
The Sengkang Depot Substation has two interconnected switchboards which serve as backups for each other, said LTA and SBS Transit. Two faults were encountered at the voltage transformer for Switchboard 2 on Tuesday, read the statement.
The first involved a high current surge due to a fault in the voltage transformer, while the second was a dislodged cable connecting to the voltage transformer.
In a normal situation, the first fault would have triggered the fuse in the voltage transformer and cut off electric current, said LTA and SBS Transit.
"However, in this situation, the dislodged cable came into contact with the metallic surface of the voltage transformer panel and allowed electric current to continue to flow, despite the fuse having been blown," they said.
As a result, the high current surge damaged Switchboard 2.
As the two switchboards were connected, the high current surge from the fault caused Switchboard 1 to disconnect from the system to avoid damage.
With one switchboard damaged and the other disconnected, power supply to parts of the NEL and the Sengkang-Punggol LRT was cut off.
Services on NEL and Sengkang-Punggol LRT were "progressively restored" on the same day using a backup power supply, said LTA and SBS Transit.
However, Switchboard 2 could not be repaired immediately "due to the extensive damage".
"As Switchboard 1 was protected from damage, it was reconnected to allow normal service to resume the next morning."
Repairs to the voltage transformer and Switchboard 2 were completed on Saturday.
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POWER CABLE FAULT
A power cable fault occurred between Farmway and Kupang stations on the Sengkang LRT on Friday, causing the entire network to lose power, said LTA and SBS Transit.
Switchboard 2 at Sengkang Depot Substation, which could have been used to provide backup power, was still out of service from the incident on Tuesday, they said, adding that service progressively resumed in the afternoon after power was restored.
LTA and SBS Transit are still investigating the cause of the cable fault, said the authorities.
Their engineers are also testing the cables along the entire Sengkang-Punggol LRT network to assess their condition.
These tests on around 28km of cables are expected to be completed by Aug 23 as they can only be carried out during engineering hours, said LTA and SBS Transit.
"As part of the Sengkang Depot expansion works, LTA will be implementing a secondary power supply source directly from the SP Power Grid, which will be completed by 4Q2025," read the joint statement.
For the longer term, LTA said it is also working with SBS Transit to make further upgrades to the power supply for the NEL and Sengkang-Punggol LRT.
