According to national rail operator SJ, an estimated 700 to 800 people on board three trains between Norrköping and Mjölby are being evacuated.
"We are evacuating them now. We are picking them up with buses. We hope to be able to run as normal tomorrow," said Ulf Wallin, deputy press director at SJ, to the TT news agency.
The line lost power at 11.49am in two places between Kimstad and Gistad, local newspaper Östgöta Correspondenten reported on its website on Tuesday.
Separately, in western Sweden, a train lift bridge in Trollhättan stuck in the upright position caused another stoppage, but train service resumed operation after 2.30pm.
In Östergötland, trains on the Stockholm-Malmö line have been diverted through Hallsberg south of Örebro instead.
"However, three or four trains on the way from Malmö are firmly out of service," said SJ spokesperson Thelma Henrysson.
Consequently, all local public transportation services in the affected areas were idled on Tuesday afternoon.
The Swedish Transport Adminstration (Trafikverket) has estimated that the damage to the wires should be repaired at 6pm, newspaper Aftonbladet reported on Tuesday, citing press officer Claes Lundstedt.
However, it has not yet issued a firm forecast on when train services will resume normal operation in Östergötland.
As of 2.30pm, an X2000 express train in Kimstad left in complete darkness had not yet been evacuated, Corren reported on Tuesday.
"For now, the trains are heated. However, if the evacuation takes time, it can understandably get be cold on board, but how quickly and how cold is difficult to answer," SJ press officer Sven-Ingvar Håkansson told Corren on Tuesday.
Buses are currently replacing the 5.11am, 6.14am and 9.15am departures from Malmö to Stockholm between Mjölby, Linköping and Norrköping, SJ wrote on its website.
Passengers travelling further towards Katrineholm, Stockholm and Nyköping will depart from Norrköping for their connections.
For passengers from Stockholm to Copenhagen, buses will take them from Linköping to Mjölby, where they will take a train to Malmö, then take the Öresund train to Copenhagen.