New Delhi: 19 states and more than 600 million Indians found themselves without power  on Tuesday afternoon, after three major grids that supply electricity tripped in quick succession. By 11 pm, power had been restored to 80% of Northern India, and all of Delhi. The country’s southern and western grids were supplying power to help restore services in the affected states, officials said.

The Delhi metro had stopped running for over an hour, and some passengers were trapped inside till an emergency supply helped trains reach the nearest station.

In West Bengal, 200 workers in four underground coal mines, who were trapped for hours after the  elevators to bring them back up stopped working, were rescued; 65 workers from Jharkhand were also rescued.  Tuesday’s massive outage – one of the world’s largest – comes just hours after North India recovered from a blackout  a day earlier when the Northern supply grid collapsed, delivering seven states and Delhi into darkness. The Northern grid went down again at 1.30 pm, followed by the Eastern Grid and the North Eastern Grid.

On Monday, Power Minister Sushil Kumar Shinde confounded many when he co-opted the crisis for bragging rights, and declared that his team had been able to restore power to most areas within six hours, considerably faster than during the last major collapse in 2001. A day later, there was no such glass-half-full analysis. The silver lining for Mr Shinde will be his promotion – he moves to the Home Ministry. There will be no full-time Power Minister for now; Minister for Corporate Affairs Veerappa Moily will hold additional charge of the portfolio. “There is no bad day to take over (a new job),” he told  on a day that will make history as one of the country’s most taxing.

Tuesday’s crisis was allegedly triggered after  three states – Haryana, Punjab and UP – drew much more than their assigned share of power. “I have told states using more power than they are meant to stop it. They shall be punished,” said Mr Shinde.   Punjab and UP have denied they exceeded their limit.

The states hit were: Haryana, Punjab, Rajasthan, J&K, Bihar, Odisha, Jharkhand, West Bengal, UP, Himachal Pradesh, Uttarakhand, Delhi and the seven North Eastern states.

The supply to Delhi at 1.30 pm was reduced to an all-time low of 40 MW against its demand of 4000 MW, bringing the capital to its knees. The metro stopped running; passengers were seen walking on the tracks to reach the nearest platform. Others were stuck inside briefly till the trains were powered up and services limped back into action.  As traffic signals went on the blink, huge traffic jams were reported from across the city.  Hospitals were left without power for a few hours; the airport, like on Monday, was not affected.

In Kolkata, the metro was not hit by the outage, but West Bengal Chief Minister Mamata Banerjee asked all government offices to shut early, and urged the private sector and schools to do the same to protect against commuter chaos in the evening.

The repeat disaster underscores India’s abysmal infrastructure and its inability to satiate the needs of a growing population and industry. Power shortages and a road and railway network in desperate need of modernization have weighed heavily on the country’s efforts to industrialize. Grappling with the slowest economic growth in nine years, Delhi recently scaled back a target to pump $1 trillion into infrastructure over the next five years.

A grid receives power from generation stations, and passes it onto load centres, which is where distribution companies pick up their share, and pass electricity onto consumers. At grids, there has to be a careful balance between the supply and the amount of power collected. A line can trip if more power is drawn than provisioned for. And a grid needs mechanisms to ensure that if one line trips, it doesn’t have a cascading or domino effect on the others.