A faulty voltage transformer at a substation was the likely cause of a 1-1/2 hour power outage last month that affected around 27,000 people.
The faulty transformer started a fire in a substation in Bright Hill, and preliminary investigations by the Energy Market Authority (EMA) suggest this led to the Jan 26 outage, said Senior Minister of State for Trade and Industry Koh Poh Koon.
Once the fire was detected, protective devices were automatically activated to isolate the fault so that other equipment would not be damaged, Dr Koh said yesterday.
This resulted in the power being cut, he told Workers' Party Non-Constituency MP Leon Perera, who had asked about the extent and cause of the incident.
The power failure hit consumers in Ang Mo Kio, Bishan, Sin Ming, Toa Payoh and Thomson, where residents reported a cut in their home electricity supply. Lifts and traffic lights stopped working.
This incident came after another major outage last September that affected more than 146,000 residents in multiple parts of Singapore, ranging from Boon Lay to Aljunied.
On whether there was a rising trend of such power failures, Dr Koh said the Jan 26 incident was the first power failure in five years involving a faulty voltage transformer.
NOT A RISING TREND
Other incidents may have happened in the recent past, but this does not necessarily indicate a systemic issue because they pertain to either different parts of the system, or could have been just due to human error. We would be worried about a trend if the same component, or the same system within the electrical grid across different substations, failed repeatedly.
SENIOR MINISTER OF STATE FOR TRADE AND INDUSTRY KOH POH KOON, on recent power failures.
"Other incidents may have happened in the recent past, but this does not necessarily indicate a systemic issue because they pertain to either different parts of the system, or could have been just due to human error," he added.
"We would be worried about a trend if the same component, or the same system within the electrical grid across different substations, failed repeatedly."
Dr Koh also said he would not draw any premature conclusions until investigations are complete.
On Jan 26, national grid operator SP Power Grid restored the power supply to 80 per cent of affected consumers in 30 minutes, Dr Koh said.
The remaining consumers had their electricity supply restored in 90 minutes.
Stressing that Singapore's power system remains among the most reliable in the world, he said that over the past six years, Singapore's average annual disruption per consumer ranged from 12 seconds to 4.2 minutes. This includes the most recent incident.
Major cities such as Osaka, New York, Hong Kong and London experienced an average disruption per consumer of between five minutes and 21 minutes in the financial year of 2017, he noted.
EMA will thoroughly investigate each incident and take regulatory action if necessary, said Dr Koh.
He added that SP Power Grid has set up an internal investigation committee to investigate the incident, and brought in experts from the original equipment manufacturer to review and advise if the failure was due to design, manufacturing or material defects.
An independent expert, Chubu Electric from Japan, has been asked to review the manufacturer's findings and recommendations.
SP Power Grid has since increased the frequency of monitoring for the specific equipment that failed, and will prioritise replacements of that particular component in future rounds of substation maintenance, Dr Koh said.