What caused the 3-line MRT disruption on Oct 14

CAUSE OF POWER FAILURE TIMELINE OF EVENTS

Marsiling Woodlands • The circuit breaker 7.34pm 8.17pm A burnt section of 22 kilovolt 3 failure caused a • An attempt to draw power from the All stranded CCL passengers reach 1 cables between Link secondary protection substation causes a second the nearest stations. station and Tuas West Road system to trip, power outage, affecting service between station triggered a power fault. cutting off power HarbourFront and stations on supply from the Tuas Tuas the CCL. 8.42pm Depot substation. Link Commuters from 11 stalled trains on Serangoon • Three trains stall as a result. NSEWL reach the nearest stations. • This affected a larger zone of Gul stations along the Circle 7.38pm 8.43pm North-South and Train service along CCL progressively resumes. East-West Lines • SMRT decides to detrain passengers on (NSEWL). Queenstown the stalled trains as it cannot restore power supply quickly. 8.44pm • As a safety measure, electrical protection Detrainment of the last train near Bukit East devices are installed to guard against the Batok station is temporarily halted due accidental turning on of traction power. Operator SMRT Clementi to rain and lightning risk, with 78 4 decided to draw • SMRT staff walk along the tracks to reach commuters still on board. power from the the stalled trains and help commuters. Buona Vista Dover Parts of lines substation, which HarbourFront with no service 9.43pm supplies power The 78 commuters alight at North-South Line 7.53pm station. to the Circle Line East-West Line Detrainment of NSEWL passengers begins. (CCL). Circle Line 10.34pm Oct 14, 6.58pm • Train services are progressively An SMRT staff • A power outage caused by concurrent faults along the Tuas West restored on the NSEWL. member and Extension shuts down train service between Woodlands and Jurong 5 supervisor East stations on the North-South Line and between Queenstown and misread stations on the East-West Line. equipment at the substation and wrongly assumed the fault in Tuas had been isolated.

Failure to isolate the fault before 6 drawing power led to a voltage dip at the Buona Vista substation, causing 7.59pm a power trip that Detrainment of CCL passengers begins. affected the CCL.

The fault activated circuit breakers 8pm The three-hour, 36-minute incident affected 2 nearby, but one failed to trip and Power supply is restored for CCL, but 123,000 commuters. Of these, 6,500 isolate the power fault as designed • This causes 12 trains to stall on the tracks. It also affects in-train SMRT does not restore traction power commuters were on the 12 stalled NSEWL trains due to a melted trip coil. lighting and air-conditioning. The backup battery on affected trains along sectors where detrainment is and 275 were on the three stalled CCL trains. kicks in to provide emergency lighting and ventilation. taking place for safety reasons.

Sources: LAND TRANSPORT AUTHORITY, SMRT PHOTOS: LTA, GAVIN FOO, ST FILE, BH FILE STRAITS TIMES GRAPHICS