A faulty transmission cable was the cause of large-scale blackouts across swathes of Kowloon East on Monday night, according to supplier CLP Power.
The power went out in more than 20 apartment blocks across Wong Tai Sin, Kwun Tong, Kowloon Bay, Ngau Tau Kok, Yau Tong and Tseung Kwan O just after 10pm.
Thousands of residents were affected, CLP Power said.
A preliminary investigation found a faulty 130,000-volt overhead transmission cable at an electricity pylon at Kowloon Peak to have caused a voltage dip which lasted for a fraction of a second.
A small fire was ignited and was put out by staff at Kowloon Peak with extinguishers. The cable was 10 years old and was last inspected last year, the company said.
When power was restored, circuits at individual buildings were overwhelmed by a sudden surge in electricity demand due to large numbers of air conditioners switched on during the hot summer’s night.
Circuit breakers in individual buildings were likely to have then tripped, said CLP chief operating officer Chow Tang-Fai, who stressed that the interruption was not an issue with the main power supply.
Chow apologised for the incident and said the problem was unprecedented.
The Fire Services Department received over 20 reports of people being stranded in apartment block lifts between 10pm and 11pm. They included residents who had to be rescued from a lift in a building on the Lower Ngau Tau Kok Estate.
The department said the fire at the pylon on Kowloon Peak, near Good Hope School on Clear Water Bay Road, was reported just after 10pm and the situation was under control by 11.10pm. There were no reports of injuries.
Power supply is a contentious issue in the city, with tens of thousands of submissions made to the Environment Bureau during a public consultation on the city’s future energy supply, which ended on June 18.
The government is considering two options: using imported natural gas to boost local generation to meet 60 per cent of Hong Kong’s electricity needs; or relying on the mainland grid for 30 per cent of these needs.
After Monday night’s blackout, one internet user on the Hong Kong Golden Forum suggested there could be much bigger blackouts ahead if the city gets its power from the less reliable mainland supply.
Separately, a CLP spokesman said on Monday that a power transformer problem left nearly a dozen customers in Tsing Yi without power at 9.38pm. By 1am, it was unclear whether the supply was back on.