Major delays and cancellations are affecting Sydney train services heading away from the city due to an power-supply issue at Central.

This is affecting the T1 Northern Line, T8 Airport and South Line, T2 Inner West and Leppington Line and the T3 Bankstown Line, according to Sydney Trains.

There are also delays on the T7 Olympic Line due to a train requiring mechanical repairs at Lidcombe.

Check here for updates.