The Circle Line disruption on 17 September was caused by a power trip, while the one on 18 September was due to a fire in one of the systems. On 26 September, SMRT issued an explanation on Facebook detailing the reasons behind the disruptions.
Background
On 17 September 2024, a power fault disrupted train services on the Circle Line for nearly two hours, affecting peak-hour travel for numerous commuters. The following day, another disruption occurred due to a fire in the power system cubicle at Kim Chuan Depot. These incidents prompted SMRT to provide a detailed explanation and outline the steps taken to prevent future occurrences.
Sep. 17 incident
A circuit breaker in the Traction Safety Shutdown System (TSSS) on the Circle Line tripped, cutting off traction power supply. The maintenance team reset the circuit breaker but decided to replace it entirely to prevent further disruptions. This action caused another circuit breaker, part of a fail-safe design, to trip, resulting in a loss of traction power across the entire Circle Line.
SMRT stated that standard protocol required the maintenance team to seek clearance from the head of Circle Line operations before conducting corrective maintenance during service hours. However, in their eagerness to rectify the fault, this critical step was overlooked. The resumption of normal train services took longer than anticipated to ensure no further technical issues were unresolved.
Throughout the night, SMRT engineers worked with the Land Transport Authority (LTA) and OEM engineers to diagnose and resolve the issue, ensuring normal train services resumed on schedule the following morning.
Sep. 18 incident
On 18 September, at around 8pm, the Circle Line Integrated Supervisory Control System (ISCS) team detected a fire in one of the TSSS cubicles at Kim Chuan Depot. This caused a power trip across the entire Circle Line, and the global emergency shutdown (GES) system was automatically activated, triggering a line-wide power shutdown.
The fire was quickly extinguished by ISCS staff, and the area was assessed by the Singapore Civil Defence Force. Once deemed safe, traction power was restored within 10 minutes, and full train services resumed at 8:15pm. LTA, SMRT, and OEM engineers worked throughout the night to conduct checks and maintenance.
Improvements to be made
An SMRT engineering team is working with LTA to review the overall design of the TSSS and GES systems. Enhancements to the Circle Line’s signalling and PA systems, as well as current fail-safe features, will be implemented. The TSSS cubicle will also be replaced with enhanced features to prevent future incidents.
Future implications
The disruptions on 17 and 18 September have highlighted the need for stringent adherence to maintenance protocols and the importance of robust safety systems. SMRT’s ongoing collaboration with LTA aims to ensure the reliability and safety of the Circle Line, especially during high-profile events like the Formula 1 period. The root cause of the fire is still under investigation, and further updates will be provided as more information becomes available.
