Energy Market Authority (EMA) has announced that its preliminary findings show that on 18 September, one of the power generating units at Sembcorp Cogen Pte Ltd (Sembcorp) tripped.
On 18 September 2018, there was an electricity supply disruption from 1.18am to 1.56am. About 146,500 customers were affected and supply was restored within 38 minutes.
EMA stated that 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.
Subsequently, EMA said that 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.
In this case, the authority noted that the protection devices in the power system automatically disconnected electricity to about 146,500 consumers to rebalance the system.
To restore electricity supply, EMA said that it had instructed other standby power generating units, including unaffected units from Senoko and YTL PowerSeraya Pte Ltd, to provide additional electricity supply.
The restoration of electricity supply was done in a controlled manner to ensure the electricity system remained stable. As electricity generation increased, supply to consumers was progressively restored over 38 minutes.
Investigations are still ongoing and EMA noted 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 said.
"We thank the public for their patience and understanding for the inconvenience caused," EMA added.