The failure of Sri Lanka’s power grid on 9 October has raised once again questions about the reliability of the island’s distribution system, with officials promising an investigation to examine ways to reduce future blackouts. Minor failures occur fairly frequently on the island’s overloaded system, which has suffered from lack of maintenance during the civil war, the danger of sabotage and even threats from its own employees’ unions, in support of pay claims, but island-wide blackouts too have occurred on a regular basis, on April 15 2007, on May 10, 2007, again in December 2007 after a thermal generator tripped and then on 21 January 21 2008

The government and state authorities have ruled out sabotage or action by electrical workers’ unions (who have been threatening blackouts if pay demands are not met) blaming instead a technical fault on one of the island’s main transmission line, which left the country without power for more than five hours from early morning and large swathes of the country without it for at least half the day. There are around 25 power plants in Sri Lanka, but if one of the main power lines trips, the whole system shuts down. The blackout occurred immediately after private companies took over some functions of the state-owned electricity company.

The immediate cause of the failure seemed to be a cable break in a key 132 000 volt transmission line in the capital Colombo from Kolonnawa to the Kelanitissa power complex of Sri Lanka’s state run power firm, Ceylon Electricity Board.

“We cannot say whether it was due to lack of proper maintenance, or natural causes or due to ageing,” CEB chairman E Edirisinghe told reporters at a hastily called media briefing where he apologised to the utilities’ customers. “We are not ruling out any possibility. A full inquiry will be conducted.”

The first failure had occurred at 1.30 am on Friday and the entire system tripped. In recent years the entire system had shown a tendency to trip, but engineers had managed to restore the system within about three hours in the past. “After the first total blackout we started restoring the supply,” says CEB general manager Badra Jayaweera. “But there was a problem of a circuit breaker at the Kotmale power station. We could not energise that circuit breaker.” Kothmale and Kelanitissa are two of the main power stations in the country, responsible for a combined 401 MW.

The main electrical workers’ union said the blackout showed the government’s transfer of some of the state-owned Colombo Electricity Board’s (CEB) work to eight privately owned companies, which took effect on Thursday, was a mistake.