[ad_1]
SINGAPORE – French company Alstom will replace all 150 km of 22 kilovolt (kV) power supply cables and circuit breaker tripping coils along the Tuas West Extension (TWE) following major train service disruption on 14 October.
To facilitate trip coil replacements, early closings will be implemented on weekends throughout TWE starting next month through the end of the year. Meanwhile, replacement work for the 22kV power supply cables started this month and will also see early closings, late openings, or full closings on Sundays throughout the TWE for a limited period next year.
“Alstom deeply regrets the inconvenience caused to Singapore travelers during the disruption of train services on the North-South, East-West and Circle lines.
“In line with our absolute commitment to operational safety, and as a precautionary measure, we are replacing all power cables to the highest specification and switch tripping coils as safely and quickly as possible,” said the vice president. Alstom Asia-Pacific Senior. -President Ling Fang at a press conference on Wednesday (October 28).
The Executive Director of the Land Transportation Authority (LTA), Ng Lang, noted that the cables along the TWE, which began commuter services in 2017, had shown similar failures on four previous occasions. This prompted LTA to raise the issue with Alstom, the main cabling contractor, in January, after which the company agreed to replace the top two layers of TWE power cables, where all the failures occurred.
Alstom will bear the cost of replacing the cable. The amount involved has not been disclosed.
“Our trains are a very complex system and only a small part of it that is not working can cause a major disruption to the entire system,” Ng said.
LTA said site investigations the day after the incident found that a 22 kV cable section located about 500 meters from the Tuas Link station was “burned out.” (PHOTO: LTA)
What happened
The three and a half hour incident, which affected 123,000 commuters and left thousands trapped in stopped trains, began with a failure in the 22kV power cable in the electrical zone between the Tuas Link and Tuas West Road stations along the TWE. While this would not normally have caused an outage, the circuit breaker at the Tuas West Road station malfunctioned due to a faulty trip coil.
As a result, the circuit breaker intended to isolate the cable fault within the electrical zone did not trip as designed. A secondary protective mechanism was activated, causing power to the Tuas Depot intake substation to shut down and disrupt power to the affected section of the North South and East West (NSEWL) lines, from Woodlands to Jurong East stations and from Queenstown stations to Gul Circle.
To rectify the situation, a member of SMRT’s power staff made the decision to draw power from the Buona Vista Intake (BVI) substation but did not ensure that the previous cable fault had been isolated. This, in turn, caused a voltage drop across the BVI, which activated the security system protecting the Circle Line (CCL) and stopped the supply of power from HarbourFront to the Serangoon stations.
Corrective actions
In a press release, LTA said that site investigations conducted the day after the incident found that a 22 kV cable section located about 500 meters from the Tuas Link station was “burned out.” LTA noted that the faulty trip coil and faulty wires have since been replaced.
The authority added that maintenance personnel also checked all TWE stations to make sure that all trip coils of the circuit breakers are working. Two trip coils were found to show inconsistent performance and were replaced on October 15. The faulty coils have also been sent for forensic examination.
“This includes visual checks of the condition of the trip coil every 10 days and mechanical tests every six months instead of 12 months. SMRT will also improve its operating procedures for energy recovery so that similar misjudgments are not repeated, ”LTA said.
SMRT: Incorrect graphics display reading contributed to Oct 14 outage, 2 workers suspended
‘Sorry’ for the problems caused by the breakdown of the MRT: Ong Ye Kung
The power failure caused the disruption of train service on the North-South, East-West, Circle lines
