NEW DELHI — The world’s largest blackout ever crippled roughly half of India for a second consecutive day on Tuesday, sending officials scrambling for an explanation.
The power failure spread across 22 of the country’s 28 states, an area whose population is nearly 700 million, almost 10 percent of the world’s population. Hundreds of trains stopped across the region and, in Delhi, the subway system stalled, and massive traffic jams collected as traffic lights stopped functioning.
But despite the scale of the power failure, many Indians responded with shrugs. In the first place, India’s grid is still being developed and does not reach into many homes. An estimated 300 million Indians have no routine access to electricity.
Second, localized failures are routine. Diners do not even pause in conversation when the lights blink out in a restaurant. At Delhi’s enormous Safdarjung Hospital, doctors continued to rush around as hundreds of patients lay in darkened hallways.
Third, so many businesses employ backup generators that, for many, life continued without much of a hiccup. Dr. Sachendra Raj, the manager of a private Lucknow hospital, rented two new generators two months ago, and they were keeping the hospital’s dialysis machines running and the wards air-conditioned. “It’s a very common problem,” Mr. Raj said. “It’s part and parcel of our daily life.”
The root cause of the vast power failure was not immediately clear. India has struggled to generate enough power of its own to fuel businesses and light homes, and the country relies on huge imports of coal and oil to power its own plants. While top government officials blamed several northern states for pulling more power from the national grid than they had been allotted, those states have been power needy for years.
It is also unlikely that power demands suddenly spiked this week since monsoon rains have lowered temperatures in recent weeks across much of northern India. An investigation has been started, with some government officials pointing to a relay problem near the Taj Mahal as the prime culprit.
The government — which controls much of the nation’s electrical grid and generating capacity — carried out a cabinet shift, announcing that it was promoting the power minister, Sushil Kumar Shinde, to the more important post of home minister. Mr. Shinde immediately tried to shift attention to the power-hungry northern states.
“I have asked my officers to penalize those states which are drawing more power than their quota,” Mr. Shinde said.
Surendra Rao, who was the chairman of the Central Electricity Regulatory Commission in 2001, when the nation’s last major blackout occurred, said that a fairly sophisticated system of circuit breakers should have prevented the failures on Monday and Tuesday. But, he said, the people manning the circuit breakers are bureaucrats beholden to state government officials, who are loath to have the power in their locality shut off — the usual prescription when power surges threaten the national grid.
“The dispatchers at both the state and the regional level should have cut off the customers who were overdrawing, and they didn’t,” Mr. Rao said. “That has to be investigated.”
Mr. Rao said he hoped the power crisis would lead ministers at the national and state levels to realize that far more of the country’s electrical infrastructure should be privatized. “These crises will force us in that direction,” he said.
Government officials claimed that power was restored by early Tuesday evening to 90 percent of those who lost power during the day. Still, a senior official at the Uttar Pradesh Power Corporation said that much of the state, including rail and water lines, were still without power at 5:45 p.m.
Prakesh Javadekar, a spokesman for the Bharatiya Janata Party, which is the main opposition party, said the blackout was “a huge failure of the management of the power sector by” the governing coalition, which is led by the Congress Party.
About 200 coal miners in West Bengal were stranded in underground mines when the electricity to elevators was shut off, according to media reports.
“We are waiting for the restoration of power to bring them up through the lifts, but there is no threat to their lives or any reason to panic,” said Nildari Roy, a senior official at Eastern Coalfields Limited, the mines’ operator, according to media reports.
Tuesday’s blackout started shortly after 1 p.m., a little more than 34 hours after Monday’s blackout began.
On Monday, some officials said the scale of the power failure was an anomaly. “This is a one-off situation,” said Ajai Nirula, the chief operating officer of North Delhi Power Limited, which distributed power to nearly 1.2 million people in the region. “Everyone was surprised.”
But on Tuesday, officials had yet to figure out why the power failure was so widespread.
“We seem to have plunged into another power failure, and the reasons why are not at all clear,”said Gopal K. Saxena, the chief executive of BSES, an electric company that services South Delhi, in a telephone interview. It may take a long time to restore power to north India, he said. Officials scrambled to get more power generation into the nation’s electricity grid.
“We are taking hydro power from Bhakhra Nangal Dam,” in northern India, said Sushil KumarShinde, the power minister, in a televised interview.
A trade body, the Associated Chambers of Commerce and Industry of India, or Assocham, said that Monday’s power problem “totally disturbed the normal life and has severely impacted the economic activities.”
Sruthi Gottipati, Niharika Mandhana and Hari Kumar contributed reporting.