High temperature caused by a sensor failure has been identified as the cause of the country-wide power cut that occurred last week.

Enemalta Corporation yesterday released the findings of an investigation carried out by its engineers into what led to a total shutdown of both power stations at 10.30 a.m. on June 16 and a subsequent shutdown on the same day at 4 p.m.

The main cause of the failure was an "anomalous high temperature" due to a sensor failure, Enemalta said. The rest of the generating units tripped moments later as a result of this fault.

The investigation indicated that a failure of what is known as the GT-9 turbine led the other steam units, particularly those at Marsa, to lose synchronisation and they subsequently tripped together with all other generating units in service at the time, Enemalta said.

In the second shutdown, the investigation revealed that the same GT-9 unit tripped due to an anomalous high temperature. Enemalta said this was therefore clearly established as the main cause of the power cuts, indicating a possible fault in the fuel or combustion system of the turbine.

The availability of reserve capacity would have ensured sufficient power to restore supply to all load, even in the event of a prolonged outage of the faulty unit, the corporation said. In this specific case, had GT-9 been unavailable following the trip, the available reserve capacity would have still been sufficient.

However, even if the reserve capacity had been higher at the time of the incident, this would not have prevented either the trip of the gas turbine or stop the cause of the tripping of the remaining generating units, which led to the system shutdown.

The report will be tabled in Parliament on Tuesday.