TNB CEO and president Datuk Che Khalib Mohd Noh said the gas leak occurred at the Port Klang power station switchyard.

Noh said the company had “about four-and-a-half hours advance knowledge” before sequential tripping occurred at the station.

The national load dispatch centre was alerted at 8am to “low gas pressure at one of the two circuit breakers connecting the bus bars at the switchyard” and dispatched an investigation team following an alarm from a circuit breaker, according to Noh.

“About 10am, the team confirmed the gas leak," he said.

"The reading of the gas pressure indicated a significant drop from the normal 7.4 to 6.4 bars. If the pressure falls below 6 bars, the circuit breaker P10 will be inoperable and cause further damage to the equipment. This will lead to an extensive shutdown of the Port Klang Power Station Switchyard.”

TNB has said it would not provide rebates to its consumers as it had managed to resume power supply within “the stipulated period set by the energy commission”.

The commission’s licensing condition is that power supply “disrupted due to minor damages must be resume within four hours” while the restoration period for major damages was 48 hours.

“The period of power disruption during the Jan 13 incident was between one hour and 30 minutes and two hours and 30 minutes for most of the affected areas,” said Noh.

But a report in the New Straits Times indicated “companies have started filing claims with either the federation of Malaysian manufacturers or state governments”. According to the newspaper, 165 companies in the state of Selangor are already seeking compensation to the tune of US$11.6 million.

The last time TNB was forced to provide a rebate, in August 1996, it cost the firm US$19.5 million.