Emergency work has been taken up on an emergency basis after the Eastern Grid collapsed at 1:00 PM, West Bengal Power Minister Manish Gupta told PTI.
Gupta said power supply is expected to be restored by evening.
Sources in the West Bengal State Electricity Distribution Company Ltd said that power generation in five plants had come down to nil.
Private power utility CESC Limited said it suffered a shortfall of 500 MW.
"We are somehow managing with whatever little power is left," a CESC spokesman said.
Railway sources said train services were stalled at Howrah, Sealdah and Asansol divisions because of the grid failure.
South Eastern Railway sources said large areas under its jurisdiction in West Bengal, Jharkhand, Odisha and Bihar were seriously affected.
Twenty-six trains were stalled in the Howrah-Kharagpur section, 11 on Kharagpur-Bhadrak and four on Kharagpur- Tatanagar sections, the sources said.
The grid collapse severely hit Chakradharpur, Kharagpur, Adra and Ranchi divisions of the South Eastern Railway, though a little power was available from Jharsuguda, Kolaghat and Santragachi.
Metro Rail services in Kolkata were being run with power drawn from CESC Limited.
Large parts of Kolkata and the adjoining areas were without power.
