Switchboard failure at substation led to power trip

The three-hour disruption of train services on the North East Line (NEL) on Aug 12 was caused by a failure of the power switchboard at the NEL depot's substation.

- Esther Loi

Preliminary investigations found that the failure caused a flashover – an unintended electrical discharge – in one of the voltage transformers used to regulate the power supply, said SBS Transit group chief executive Jeffrey Sim on Aug 12.

This led to a power trip in both the main and backup power supplies as part of the power protection mechanism, he added.

A voltage transformer reduces a high voltage to a lower, safer level, while a power switchboard distributes power from electric sources to several smaller circuits.

The trip at 11am crippled services on the NEL along an 11-station stretch between Farrer Park and Punggol Coast, as well as the entire Sengkang-Punggol LRT.