Commuters have been given a taste of the train strike chaos expected later in the week, with a string of rail delays and cancellations across the network on Tuesday morning.

A broken-down train at Melbourne Central at 7.45 am caused long delays on the Cranbourne, Frankston and Pakenham lines. The train wasn't cleared for an hour.

Commuters faced rail delays on Tuesday ahead of a threatened rail strike later in the week. Credit:Penny Stephens

Separately, there were further delays of between 15-20 minutes on the Frankston line due to a power supply problem between Highett and Bentleigh.

Trains on the Frankston and Pakenham line were also running direct to Flinders Street, rather than via the City Loop.