The northern grid crashed early on Monday in one of the worst outages in more than a decade, plunging eight States into darkness, affecting inter-State train operations and health services and impacting millions of lives.

The 400-kV Bina-Gwalior line, feeding the Agra-Bareilly transmission section, tripped at 2.35 a.m. and wreaked havoc on the generation and transmission systems, shutting down all major plants, including hydropower stations, in Punjab, Haryana, Rajasthan, Delhi, Uttarakhand, Himachal Pradesh, Jammu and Kashmir and the Union Territory of Chandigarh, all wired to the northern grid. The immediate impact was shortage of around 32,000 MW.

India now faces 8-12 per cent peak power deficit, according to the Central Electricity Authority (CEA).

The shutdown had a crippling effect on inter-State passenger and goods trains that came to a halt. Early morning office-goers and schoolchildren had a harrowing time, as signals were on the blink, sparking traffic chaos.

Hospitals scurried around for backup supply. A majority of the hospitals claimed to have alternative arrangements, yet health services were affected at several places. But the major oil refineries at Panipat, Mathura and Bhatinda remained unaffected as they have their own captive power plants.

While Union Power Minister Sushil Kumar Shinde said he could not pinpoint the reason, officials of the Power Grid Corporation of India Limited (PGCIL) and the Northern Region Load Dispatch Centre (NRLDC) said rampant over-drawal by Uttar Pradesh, Punjab and Haryana sparked the collapse.

The NRLDC is the apex body tasked with ensuring integrated operation of the power system in the region.

When the grid collapsed last time, in 2001, the supply snapped at midnight, and normality was restored by 4.30 p.m.

PGCIL Chairman and Managing Director R.N. Nayak said normality was restored by 4 p.m. The northern grid, which caters for 28 per cent of India’s population, was generating 29000 MW by late evening, about 2,000 MW of the peak demand.

Immediately after the collapse, PGCIL officials swung into action, with Mr. Nayak and his team reaching their monitoring centre at 3 a.m. to assess the situation and work on rescue measures. By 8 a.m., they claimed to have restored 40 per cent of the supply. To run essential services, power was diverted from the western and eastern grids to the northern region. Hydropower was imported from Bhutan.

Mr. Nayak could not say what caused the collapse, but said the agencies involved were at least “quick at restoring normality at a record time.”