Passengers experienced 45 minutes delay from Swansea to Cardiff Central this morning, as a double lighting strike on signals.
The line Cardiff-Bridgend remains closed. Arriva Train Wales (ATW) said they are diverting trains via the Vale of Glamorgan line through Barry but the damage was affecting the Valleys lines as well.
Last Wednesday around midnight a double lighting damaged the signal in the Llantrisant area. ATW said the problem had to be fixed by this morning at 4am. Engineers are still at work but the problem is not solved yet.
Yesterday ATW recorded delays on five of the Valleys lines. Some of the train service were substitute with bus going from Cardiff to Bridgend, and calling at Pontyclun, Pencoed and Llanharan.
First Great Western passengers also experienced delays when travelling to Pembrokshire and through Cardiff Central.
Peter Leppard, ATW's operations director told BBC Radio Wales that the damages are severe and will not be repaired quickly.
Photo: Alex Drennan