SINGAPORE: The blackout across multiple estates in Singapore early on Tuesday (Sep 18) was caused by the tripping of two power-generating units, one at Sembcorp Cogen and the other owned by Senoko Energy, said the Energy Market Authority (EMA) on Wednesday.
"Our preliminary findings show that on Sep 18, one of the power-generating units at Sembcorp Cogen Pte Ltd (Sembcorp) tripped.
"The stability of the power system requires the electricity supply to constantly meet electricity demand. When a power-generating unit trips, the other units in operation will increase their electricity supply automatically," EMA explained in a media release.
"Subsequently, one of the power-generating units owned by Senoko Energy Pte Ltd (Senoko) tripped while it was ramping up additional supply. The tripping of the two power-generating units resulted in insufficient electricity supply to meet demand," it added.
About 146,500 customers were affected by the blackout.
Housing estates hit by the supply cut included Boon Lay, Choa Chu Kang, Clementi, Jurong, Pandan Loop, Aljunied, Bishan, Ang Mo Kio and Thomson.
EMA added that power was "progressively restored" over 38 minutes with the help of other standby power-generating units.
"To restore electricity supply, EMA instructed other standby power-generating units, including unaffected units from Senoko and YTL PowerSeraya, to provide additional electricity supply.
"The restoration of electricity supply was done in a controlled manner to ensure the electricity system remained stable," said the authority.
EMA said investigations are ongoing, and that it is working with Sembcorp, Senoko and their equipment suppliers to establish why the units tripped.
"We will also look into additional measures that can be put in place to minimise the recurrence of such incidents," it added.
Power utilities company SP Group had earlier apologised on Twitter, saying preliminary investigations showed that the incident was caused by a "partial loss of supply from two power generation units".
Many residents in the affected areas had taken to social media to share photos of the blackout. Speaker of Parliament Tan Chuan-Jin also chimed in, describing it on his Facebook page as "quite a serious and extensive blackout".