LAHORE, Sept 24: The nationwide power breakdown on Sunday was caused by a fault in the Rawat-Lahore 500kv line which triggered a chain reaction in the entire transmission system of the Water and Power Development Authority.

This was stated by Wapda chairman Tariq Hamid at a late night press conference. He said one of the three transmission lines from Rawat was shut down for routine repair. At around 1.30pm, one of the functional lines developed a technical fault and collapsed, transferring its load to the other line that could not sustain it and tripped. The fault flowed backwards to Tarbela dam, shutting down the generation work and starting the cascading process in the system.

When around 3,400mw from Tarbela dam went out of the system, the entire load was transferred to Mangla dam, independent power projects and Wapda’s thermal units. None could take the snowballing load and started shutting down one after another. In 10 minutes, the entire generation and transmission system collapsed.

The chairman said that 80 per cent of the power supply had been restored by 10pm and the rest would be restored by midnight. Thirteen out of 14 machines at Tarbela dam were working.

The restoration of the remaining 20 per cent of the system was delayed because some Wapda units were gas-fired and would take two to three hours to return to full operation, he said.

A three-member committee formed on the directive of Prime Minister Shaukat Aziz would submit its report in 48 hours and the authority would share the findings with the press and the nation, he said.

The chairman apologised to the nation for the ‘massive psychological’ and financial losses caused by the breakdown. He said Wapda had suffered a loss of Rs200 million in lost billing. However, he added, the equipment did not suffer any damage.

He regretted that Wapda had not learnt lessons from similar breakdowns in the past.

He said Wapda would focus on developing an ‘isolating capacity’ in the transmission system, which meant that “faulting lines could be quarantined” and the rest of the system was saved from collapse.

The chairman said he felt sorry for political rumours. He said it was a purely technical fault, but gave birth to wildest speculations of ‘every sort’.