Faulty cables will be replaced and work processes improved to identify and isolate faults for faster rectification of issues.
The Land Transport Authority (LTA) has completed its investigations into the train service disruption on the Circle Line (CCL) on 20 September 2011 that affected about 27,000 commuters. LTA has ascertained that the disruption was caused by faulty power cables that affected traction power to the trains.
Checks conducted on all DC cables; damaged cables replaced
2 Immediate investigations conducted after the incident found that the disruption was caused by a damaged direct current (DC) cable at Dakota station. In addition, it was found that the deterioration of the defective cable was exacerbated by the presence of water in some cable pits. LTA had then instructed its contractor to replace the damaged cable at Dakota station and to conduct checks on all DC cables that were installed for the CCL. The checks uncovered three other cables at risk which had since been replaced by the contractor.
3 Subsequent laboratory tests conducted revealed certain manufacturing defects in some batches of these cables as well as damage in some cables sustained during the installation process. While these defects do not immediately impede the functioning of the cables or affect MRT operations, LTA will nonetheless embark on a planned cable replacement programme to replace the defective cables for greater MRT reliability. In the meantime, checks will be done every three months to identify if any cables have deteriorated and, if so, they will be changed immediately. The full completion of the replacement programme is targeted for end December 2015, and the costs will be borne by the contractor.
4 CCL passenger service will not be affected during the cable replacement programme. As a precautionary measure, while the cable replacement programme is ongoing, SMRT will conduct insulation tests on the cables more frequently so that any signs of cable failure can be detected early and rectified. SMRT will also continue to regularly inspect cable pits and ensure that they are dry at all times.
5 Learning from the incident, LTA has worked with SMRT to improve the work processes to identify and isolate cable faults, so that the traction power and train service can resume within a shorter time. LTA has also put in place more rigorous factory acceptance tests to check such cables and tighter procedures to supervise the cable installation process to reduce the risk of cable damage.
6 As LTA’s findings showed that SMRT is not at fault for the damaged cable, no penalty will be imposed on the operator for this incident.
Passenger Safety was not compromised during the disruption
7 LTA would like to assure the public that during the disruption and recovery process of this incident, commuter safety was at no time compromised. For commuter safety, the rail system is equipped with a safety feature that will temporarily shut down train service in the event of a power trip. This allows for sufficient time to isolate the problem. Train service is only resumed when the system is confirmed to be safe.