An electrical expert from the Institution of Engineers on Monday said the public should be prepared for more power supply issues due to global warming causing more extreme weather conditions.

A voltage dip at a CLP power plant in Tuen Mun on Saturday resulted in more than 100 cases of people trapped in lifts.

It was the second voltage dip involving CLP Power in eight days, and the third this year.

Edward Lo, from the institution's electrical division, said the vast majority of dips worldwide were caused by external factors, such as thunderstorms and wildfires affecting overhead power cables.

He noted the dip on Saturday happened during a thunderstorm warning.

Lo said newer lifts need to fit a device to deal with these dips, and the government should consider subsidising their installation in older elevators.

"Maybe the government and power companies can consider setting up a fund to help homeowners who can't afford the devices [such as] the 'voltage dip ride-through devices'," he said on an RTHK programme.

The engineer added that while putting power cables underground can minimise the risk of external factors, such a move would be very expensive.

Roundtable lawmaker Michael Tien proposed fining power companies for disruption caused by voltage dips, as an incentive and pressure to avoid repeated problems.

He said, for example, that for each lift disruption, the firms should pay a HK$10,000 fine to the government, and HK$1,000 to each person trapped.

Tien agreed with Lo that it would be too costly to build underground power cables, saying fitting the ride through devices in lifts may be a better solution.

However, the chairman of Legco's environmental affairs panel, Edward Lau, said CLP and the government should still consider underground networks.

He said the Northern Metropolis involves many development plans which require enhanced infrastructure.