Services on Friday evening and early Saturday were disrupted after power was switched off on safety grounds when water leaked into overhead lines following heavy rain.
Grand Central and Northern trains were affected with Metro announcing that all its Christmas Eve services between Pelaw and Park Lane “will be unable to operate”.
The station was already due to close at 2.45pm owing to what rail operator Northern has described as “RMT industrial action impacting staffing numbers”.
Northern later said: “Following a problem with the electrical supply at Sunderland all lines have reopened and all remaining trains are now able to operate as booked.”
The trains now expected to call at Sunderland as scheduled are the 10.31am Middlesbrough to Newcastle, 11.32am Middlesbrough to Newcastle and 11.40am Newcastle to Middlesbrough services.
A Metro statement earlier said: “Metro services between Pelaw and Park Lane will be unable to operate on Saturday, December 24, due to damage to overhead line equipment at Sunderland Station and the planned national rail strike.
“Following a period of heavy rain on Friday, December 23, water leaking onto overhead line at Sunderland Station meant that for safety the power to overhead line equipment had to be turned off by Network Rail, who manage the infrastructure between Pelaw and Park Lane.”
Metro tickets will be accepted on certain Go North East and Stagecoach buses until 3pm.
More details are available at www.nexus.org.uk/metro/updates?open=t_disruptions
Further information about Northern services is available at www.northernrailway.co.uk.
Grand Central can be contacted on 0345 603 4852 while National Rail Enquiries is available on 03457 484950.