The Metro service has been fully restored between Pelaw and Brockley Whins after a three day disruption.
The disrupted section of line was re-opened to Metro trains at the start of the day’s timetable.
Network Rail, who own and manage the Sunderland line, carried out the repairs overnight.
A Network Rail spokesman said: “Our engineers worked through the night to replace a damaged power cable.
“We are delighted this work was completed successfully despite the weather conditions on site, allowing a normal service to operate from start of service this morning.
“We apologise to passengers who have been disrupted by this fault.”
Nexus is the public body which owns and manages the Tyne and Wear Metro service.
Head of Communications and Customer Services at Nexus, Huw Lewis, said: “I’m sorry for the disruption which has been caused on the Sunderland line over the last few days.
“It has been frustrating for passengers and I’m grateful for their patience while Network Rail fixed the problem.
“I’m pleased to say that the repairs to the power supply were completed overnight and we are able to run Metro trains between Pelaw and Brockley Whins.”
Sharon Kelly, Managing Director at DB Regio Tyne and Wear, which operates Metro on behalf of Nexus, said: “I would like to apologise to customers for the disruption to services over the last few days and thank everyone for their patience during this frustrating time.”