A fault in the ‘control air’ system of Boiler 7 at the Marsa power station seems to have been the cause of yesterday’s power outage, Enemalta said in a statement.
Boiler 7 tripped at around 4.10 p.m. causing a total shutdown of the electricity systems.
At the time, this was the only boiler in use at the Marsa station with the rest of the load being supplied by the Delimara station.
Boiler 7 was at the time supplying steam to the turbines that were generating 67MW, which was 25 per cent of the 251MW, the total load required at that time.
Enemalta said it was concentrating generation at Delimara whenever possible to minimise emissions and optimise the generation of electricity using the most efficient generation units.
When the boiler tripped, the 25 per cent of the load was transferred to the Delimara station, which at the time was unable to meet the sudden demand, resulting in a massive and fast drop in system frequency.
This triggered the automatic protection devices, which monitored the system in case of overload, to protect the generators in service by tripping them. This led to a total shut down of all generating plants.
Although the cause of the tripping in Boiler 7 was still being investigated, it appears that a fault in the ‘control air’ system lead it to trip.
The control air system provides air for the boiler instrumentation, control valves and actuators and any failure resulted in an automatic shutdown of the boiler.
Enemalta said the boiler was successfully restarted shortly after the trip and was currently being used on test to supply steam to internal auxiliaries in the power station.
At present, Enemalta has sufficient available capacity to meet the peak demand with over 60MW in reserve, the corporation said.
It said that supply yesterday started to be restored at 4.35 p.m. at Mater Dei Hospital, the Freeport, Marsascala, Tarxien, Marsa and parts of Sliema and Msida.
Electricity was later restored to the rest of Malta and at 7.45 p.m., power was restored to 70 per cent of the island. Electricity was fully restored to all areas at 8.47 p.m.
Enemalta said the new generating plant at Delimara would help prevent similar incidents as it would be composed of eight small 18MW generating units which would limit the impact of a single unit trip to a small percentage of the total load.
Similarly the planned interconnector would provide a source of instantaneous reserve capacity. The Maltese islands would no longer be an isolated system and this would lead to increased security and reliability of supply.
Enemalta said that no one was injured during yesterday’s incident and it thanked its engineers, technicians and other employees who did their utmost to restore supply in the shortest time possible.
It apologised to the public for any inconveniences caused.