In most of the major cities and towns electricity would be restored by 7-7:30 PM, Nayak told reporters giving an update on power situation.
State-run Power Grid Corporation of India, which controls the country's transmission network, said that situation across the country is expected to be normal by midnight.
"We are trying to restore (power to normalcy) all over the country by midnight," Nayak said.
Pushing more than half of the country's population into power crisis, three major transmission grids -- Northern, Eastern and North Eastern -- collapsed by 1300 hrs.
At present, the Northern Grid is getting power from Gwalior and Agra substations as well as from three hydel projects -- Tehri and Vishnu Prayag in Uttarakhand and Nathpa Jhakri plant in Himachal Pradesh, he said.
According to Nayak, about 9,000 to 10,000 MW have been restored so far across all the three regions, where is demand is around 55,000 MW.
More From This Section
When asked about the possible reasons for the grids' failures, Nayak said, "Some sections might have caused tripping but it is difficult to give you anything at this time. We are trying to fix the problem".
Except for few areas in Kolkata and Delhi, and Narora (Uttar Pradesh), the entire regions were affected, he said.
At the time of failure, Northern Grid's demand was about 32,400 MW, Eastern Grid (12,000 MW) and North Eastern Grid (1,100 MW), respectively.
Currently, Nayak pointed out that 17 to 20 per cent power has been restored in the Northern Grid while it is around 20 per cent in the Eastern Grid. About 50 per cent has been restored in the North Eastern Grid.