HK Electric maintenance staff sparked a major power outage that caused blackouts across Hong Kong, the company has admitted.
The firm said late on Thursday that staff members at a switching station had connected a backup cable, last used more than 10 years ago, by mistake in the early hours of Wednesday and caused the outages.
“This activated an automatic protection mechanism and affected the electricity supply,” Francis Cheng Cho-ying, the HK Electric operations director, explained.
Ip Sung-tai, HK Electric’s general manager, said the backup cable was not marked on the circuit diagram of the station and the company was still investigating why it had not been included.
Cheng emphasised that the power cut was a “rare” and “one-off” incident and that the company would stick to its deal with the government when asked whether it would issue tariff subsidies as compensation to customers.
Wednesday’s outage, caused by a voltage dip, lasted 48 minutes, from 12.49am to 1.37am.
The Electrical and Mechanical Services Department were alerted to the disruption at around 1.27am.
HK Electric officials apologised to affected customers and promised they would carry out a review in a bid to prevent a repeat.
The company said the incident happened at its Cyberport switching station in Pok Fu Lam, which houses a 275kV supply system.
Ip said the cable had remained connected to the system with no markings to show its backup status. When it was plugged in, it caused a short circuit.
He explained that the cable was not equipped with its own protective device, so it took technicians longer to isolate the problem, which triggered a chain reaction that affected the power supply in areas across the city.
Ip said maintenance work at the Cyberport switching station had been halted and staff ordered to check the accuracy of circuit diagrams of the plant and add markings to all backup cables.
He was speaking after the government said it was concerned by the incident and that the department had asked HK Electric to submit a detailed report within four weeks.
The Fire Services Department said it had received 30 reports of people trapped in lifts and dealt with 37 automatic fire alarm activations during the power cuts.
Police said between 10 and 20 sets of traffic lights were still out of order at 6.25am on Thursday, and the Transport Department told road users to “drive with utmost care and patience” in Central, Western, Eastern, Southern and Wan Chai districts.
HK Electric’s HK$493.3 billion (US$50 billion) net assets would yield an additional return of HK$7.4 million under the agreement as there was an 0.015 per cent incentive adjustment for power restoration inside 65 minutes.
But Hong Kong Island East lawmaker Edward Leung Hei took aim at the incentive scheme.
“The two utilities are guaranteed a yearly return of 8 per cent, which is a big sum. This is already great encouragement and reward for them to provide a stable electricity supply,” he said.
Leung added that the government should consider cutting the time frame for utilities to qualify for rewards after a power cut.
Leung, of the Democratic Alliance for the Betterment and Progress of Hong Kong, said that human error and natural causes should be accounted for separately in performance incentives and the penalty system, and that human error should result in sanctions.
The Environment and Ecology Bureau will carry out an interim review of the control agreements with HK Electric and CLP Power this year.
Environment minister Tse Chin-wan earlier said any changes to the terms had to be agreed with the city’s two suppliers.
William Yu Yuen-ping, an energy economist, agreed the government could consider the nature of outages in its mechanism.
But Doreen Kong Yuk-foon, a lawmaker and Election Committee member, disagreed there was a need for an overhaul of the performance incentives system.
“Launching an overhaul due to one incident, I can’t come to that conclusion as it doesn’t seem fair, but I hope HK Electric will review their performance after this,” Kong said.
The lawmaker, who lives on Hong Kong Island, added that she would consider other factors, such as tariff levels, to decide whether the companies deserved the rewards.
The Environment and Ecology Bureau said it would conduct an audit with the power companies every year, covering their technical, environmental and financial performance.
Customer performance would be among the factors used to determine proposals for the incentive and penalty mechanism.
“We will follow up in the auditing review of the year and examine whether this power supply incident will trigger the relevant incentive and penalty mechanism, a bureau spokesman said.
“We will take into account the public’s views, the performance of the two power companies in the past few years and the latest economic environment.”