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Christchurch's eastern power network is under pressure as winter approaches, lines company Orion says.

About 5000 Christchurch customers in the eastern suburbs have been hit by power outages in the past week.

Network overloading during colder weather, as well as storms and quake-damaged cables, contributed to the outages.

The outages had increased the fragility of the power network in the area and it was important customers minimised their power use to ease the pressure, Orion said.

The eastern network did not have enough capacity to meet heavy demands for electricity as colder weather set in, it said.

It had begun urgent work on a new substation and temporary 1.5km overhead 66kV line in New Brighton, to replace a damaged Orion substation and make the network more resilient to cope with demand.

However, fewer than 2000 customers were connected to eight generators in the eastern suburbs and Orion expected to have those customers back on the main power supply within three weeks.

Meanwhile, power had been restored to about 60 per cent of the central business district within the four avenues.

Most customers without power were within the red zone, which was badly hit by the quake.