SINGAPORE - SMRT and the Land Transport Authority (LTA) have identified three possible causes for the power trips on Tuesday evening, which eventually led to a shutdown of the North-South and East-West lines for over two hours during the evening peak period.
After doing a walk through the tunnels, engineers found that the insulation on two power cables along the North-South line were damaged.
There was also a faulty voltage relay at the Kranji power substation and water leakage along a section of the Tanjong Pagar tunnel .
All these damaged components have been fixed or replaced, said SMRT's managing director of trains Lee Ling Wee at a press conference on Wednesday morning.
He added however that they could not be "100 per cent certain" that these were the causes of the power trips and SMRT engineers will continue to check through the system after revenue service on Wednesday.
On Wednesday morning, trains were running as per usual at headways of two minutes during the morning peak period.
While the operator had planned to shut down service from 11am to 4pm, they found that trains were running smoothly and decided to continue service as per normal throughout the day.
Mr Lee at the press conference also explained what happened on Tuesday evening leading up to the disruption.
At about 6pm, there were more than 20 counts of traction power trips across the network. These were remotely reset by officers manning the Operations Control Centre.
Power trips occur when the train system detects a surge of power in the system and as a precautionary measure shuts down.
However around 7pm, there were three power trips that could not be reset remotely and needed to be done at the station level.
As the cause of the power trips could not be isolated, SMRT decided to shut down the NSEWL lines after detraining passengers at station platforms, he said.
SMRT ran trains along the westbound and eastbound lines first and found that trains could function smoothly but hit snags along the north and southbound lines.