Commuters can expect minor delays getting home after an earlier power outage caused lengthy wait-times on train lines running through Central Station.

A spokeswoman for the Traffic Management Centre said earlier that while the power supply problem had been fixed it would take "some time" for services to return to normal.

Sydney Trains apologised to customers affected by the problem and said small delays were expected for Thursday's evening peak.

"There are some delays to services across the Sydney Trains network affecting the T1 North Shore, Northern and Western, T2 Inner West and Leppington, T3 Bankstown and the T8 Airport and South lines," a spokeswoman said.

"Buses are supplementing services where required."