This picture taken on April 6, 2023 shows illuminated neon signs in Hong Kong. (PHOTO / AFP)

The 48-minute blackout on Wednesday that affected various districts of Hong Kong Island was caused by engineers’ mistake of accidentally connecting a undocumented backup cable to the power system during maintenance, a preliminary investigation of the Hong Kong Electric showed.

Francis Cheng Cho-ying, the operating director of the company, deeply regretted this accident and sincerely apologized to the customers affected. He explained that this incident is an isolated incident, rarely seen in the company’s history

Ip Sung-tai, general manager of HK Electric’s power transmission and distribution department, told reporters on Thursday night that the mishap occurred at an electrical station in Cyberport. It caused a short circuit and a sudden drop in voltage, triggering the automatic protection system.

He noted that Hong Kong Electric listed the cable as a backup when it carried out a project to improve the power grid more than ten years ago. The cable has been connected to the system, but was maintained in a state without electricity.

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It was also not included in the circuit data used by the engineer during maintenance, so the on-site procedure did not cover the methods about how to handle problems caused by the cable..

Additionally, the HK Electric found another backup cable in the Cyberport station after power outage and immediately stopped the maintenance work. The company will comprehensively review the accuracy of the power system circuit diagrams and add notes to the backup cable information to ensure that engineers will pay additional attention in this aspect in future works.    

Francis Cheng Cho-ying, the operating director of the company, deeply regretted this accident and sincerely apologized to the customers affected. He explained that this incident is an isolated incident, rarely seen in the company’s history. He added that the quality of power supply of HK Electric is among the highest in the world.

The company will thoroughly investigate the mishap and take measures to prevent similar incidents. It will also submit a detailed report within four weeks in accordance with the requirement of the government, Cheng said.

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The Secretary for Environment and Ecology Bureau of the Hong Kong SAR said that it is very important to have a stable and reliable power supply in Hong Kong that is an international city. That is why the government asked the HEC to submit a detailed report within four weeks to explain the cause of the incident, so as to prevent its recurrence, the secretary added.