Hunt for cause of MRT shutdown goes on
RAIL operator SMRT has identified three possible causes of Tuesday's unprecedented breakdown on the North-South and East-West lines: worn cable insulation, tunnel water leakage and a glitch in a power substation.
Even as trains ran smoothly yesterday after these flaws were rectified, the operator said it was "not 100 per cent sure" that they led to the breakdown, and that it was continuing investigations to determine if there were other causes.
The operator - which has been in the spotlight since two major disruptions in 2011 triggered a public inquiry - said it found two power cables at Bishan Station with "slightly worn" insulation.
It also found a "no voltage relay" (a type of safety switch) at a substation in Kranji that was faulty. And in a tunnel at Tanjong Pagar Station, there was water leakage close to a power-supplying third rail.
These flaws, it said, could have sparked electrical anomalies that led to power trips across the network.
SMRT could not find any flaw in a new train that was initially suspected of contributing to the shutdown, but the train has been removed from service for further checks.
Asked if these three potential flaws would have been picked up during routine checks, SMRT Trains managing director Lee Ling Wee said: "Our routine checks do cover these things, but they are not done every day, they are done six-monthly or annually."
He acknowledged that as a system ages, the frequency of checks need to rise, adding that SMRT was putting in place "conditioning monitoring systems" that will help it do this, but it takes time to do so.
Condition monitoring systems are widely used in the power generation, petrochemical, pharmaceutical, wafer-fab and other high-tech industries to detect changes that might be indicative of an imminent component failure.
Responding to a query on how a power anomaly at one spot in the system could trigger multiple power trips elsewhere in the network, the Land Transport Authority (LTA) said it was designed in such a way for safety.
But LTA senior group director of rail Sim Wee Meng said the authority is exploring newer systems that can isolate trips. "This system is quite new, and we are testing it on the Downtown Line," Mr Sim said. "Once we determine it is a good system, we are likely to roll it out to other lines."
Making his first public appearance since the breakdown on Singapore's two oldest and most heavily used lines 16 hours earlier, SMRT chief executive Desmond Kuek said even if the company stepped up maintenance, it "will still not be able to catch every one of these potential faults". "So one solution is to completely renew the system," he said.
Mr Kuek explained that SMRT was doing all it could to make the network more reliable, but priority had to be given to fixing flaws in the third rail (identified as the main culprit in the 2011 incidents), replacing rail sleepers (which affects safety) and renewing the signalling system (to cope with soaring ridership).
"All these are multi-year programmes," he said. "And all these are being done while new trains are introduced into the system, and need to be tested and commissioned."
At the same time, SMRT is focusing maintenance efforts on "hot spots" such as the problem-prone Yew Tee-Kranji stretch.
"All these are conflicting sets of priority in terms of resources, time and manpower," Mr Kuek noted.
National University of Singapore transport researcher Lee Der-Horng said the latest breakdown "exposed the weak resilience of the system".
"I wonder why the system was configured in such a way in the first place," he said.
Yesterday, Prime Minister Lee Hsien Loong weighed in on the incident.
"(I) am very concerned at the major disruption to train services last night," he said on Facebook. "I had just recently visited the SMRT Bishan Depot, to see their maintenance operations and teams. So I went to the LTA Ops Centre this afternoon, to be briefed on the situation.
"Today, fortunately, trains ran without a glitch, so far. But because we have not identified the root cause of the power trips, we are still very worried that the problem may recur."