Blackout forces Sydney tourists down tower

Tourists and staff have had to walk down Sydney's longest staircase - a whopping 1504 steps - during a blackout at Centrepoint Tower in the city centre.

The group went down the 309m building shortly after noon on Thursday.

Fortunately, emergency lighting meant they did not have to do it in the dark.

It was one of many problems caused after a power outage in the CBD stalled lifts, triggered evacuations and created commuter chaos.

One staff member was briefly trapped in a lift near the Centrepoint summit but managed to open the doors, a spokeswoman said.

About 1100 premises along several city blocks were blacked out as a precaution after Ausgrid found a fault with underground cabling.

Traffic lights went blank and sections of Pitt Street were closed, while thousands of lunchtime shoppers had to be moved from Westfield Sydney shopping centre.

A hearing for two men charged with planning a terrorist attack was delayed by more than two hours after Central Local Court was shut down.

Ausgrid says power has been returned, but Centrepoint Tower remains closed.