SAFETY MECHANISM AGAINST MAJOR BLACKOUT

Dr Warren Lee asked the Minister for Trade and Industry, in view of the recent major blackout in Singapore resulting from the sudden and accidental reduction in gas supply to our power stations, whether any safety mechanism exists to protect Singapore from suffering a repeat of such incident.

The Minister of State for Trade and Industry (Mr Raymond Lim Siang Keat) (for the Minister for Trade and Industry): Sir, a disruption in the natural gas supply from West Natuna, Indonesia led to the tripping of seven gas fired generation plants at 10.00 am on 5th August 2002.

About 1,550 MW of generation capacity was suddenly lost from the system which was drawing about 4,650 MW. Load amounting to 380 MW had to be shed to bring demand down to a level that will not overload the remaining generation capacity still operating in the system.

Electricity supply was fully restored by 11.28 am.

What caused the natural gas supply disruption? Natural gas from West Natuna is conveyed by a pipeline that terminates at Conoco's Onshore Receiving Facility (ORF) in Sakra on Jurong Island.

During a routine maintenance carried out by Conoco at the ORF, an emergency shutdown (ESD) valve was automatically activated. This disrupted the natural gas supply to SembCorp Gas and its gas customers. The activation of the emergency valve is part of the protection design to prevent unsafe conditions in the gas network such as over-pressure. Conoco has reported that a false alarm from one of the monitoring instruments activated the emergency valve.

The gas-fired plants, although designed to also run on diesel, could not switch over from gas to diesel in time as gas pressure was lost very rapidly. Instead, four standby diesel-fired turbine generators were pressed into service. It took about half an hour to bring all these units into operation from a cold start. This stabilised the system, and thereafter electricity supply was restored to the affected areas progressively.

As the emergency shutdown valve was accidentally tripped, Conoco has stopped all non-essential maintenance work at the ORF until investigations are completed. They have also changed the computer logic by temporarily disabling tripping by this instrument in the automated safety system. Any tripping will be done manually.

A Task Force comprising members from the industry and the Energy Market Authority (EMA) has been set up to identify all likely factors that could activate the ESD valve and cause gas disruption. The Task Force will review operating procedures and identify additional preventive measures to be taken to minimise, if not avoid altogether, future disruptions.

The Task Force will take a month to complete its review.

EMA is separately studying with the power companies if it is possible for the gas-fired generation plants to switch quickly over to diesel before the gas supply depletes.

The likelihood of such sudden supply disruptions will be reduced when we have more sources of piped natural gas. As Members know, we will have another pipeline carrying gas from Sumatra next year. We intend to connect these separate pipelines and networks together. Interconnection will enable us to have gas from one source backing up supply from another, thus giving our system greater resilience. This can be done within five years. In the longer term, liquefied natural gas could be yet another fuel source. Presently, we use piped natural gas which cannot be stored. If we decide to use LNG as well, we will have a store of gas for emergency purposes.

The public was understandably concerned that a disruption in gas supply could have caused such blackouts over parts of Singapore. We are not taking this incident lightly. It will be thoroughly investigated, and lessons will be learnt. The EMA and the power companies will spare no efforts in making our electricity system more resilient against fuel supply disruptions even as we move towards greater use of natural gas in the future.