Metro Railway services were disrupted for an hour on Friday morning because of a power snag at a substation near Central station.

A substation receives power from CESC before feeding it to Metro stations. “The Central substation has two transformers. Power supply to one of them was snapped after a cable got ruptured on Thursday night. A single transformer had to take the entire load from Friday morning. After a few hours, the power tripped,” said a Metro official.

“The snag was reported at 11.25am. Normal services were restored at 12.26am,” Metro spokesperson Indrani Banerjee said.

In the intervening period, a truncated service was operational, said officials.

Trains ran between Maidan and New Garia stations in the south and between Dakshineswar and Girish Park in the north. The stretch between Central and Maidan was out of bounds for an hour.

Both Girish Park and Maidan stations have provisions for trains to change directions.

Another official said the third rail’s supply was not affected after the power tripped. “But the station’s lights, fan and panel rooms were not receiving power,” he said.

The snag’s impact could have been much more pronounced had it not happened on a holiday (Good Friday).