On July 30 and 31, 2012, the synchronously-connected NEW (Northern–Eastern–Western–North-Eastern) grid in India collapsed on two consecutive days.

The pre-conditions on both days were the same: a failed monsoon left the Northern Region under heavy load while the Western Region was under-drawing because of rains, producing a skewed inter-regional flow pattern. NR was importing roughly 5,767 MW from neighbouring grids on the night of July ²⁹⁄₃₀, 1,400 MW of which was on three HVDC links (Mundra–Mohindergarh, Vindhyachal back-to-back, Pusauli back-to-back). The 400 kV Bina–Gwalior–Agra-2 had been under planned shutdown since July 28 for upgrade to 765 kV, and additional 220 kV and 400 kV elements between WR and NR tripped over the evening of July 29.

30 July 2012, 02:33 IST. The 400 kV Bina–Gwalior-1 line tripped on the depleted west-to-north corridor; cascading separations of the remaining inter-regional links followed within seconds. The Northern Region islanded from the WR/ER grids and frequency in NR fell below 47.5 Hz within 6.5 seconds, causing under-frequency tripping of generators across the region. NR’s load-shedding scheme was sized for 10,000 MW (4,000 MW flat-frequency UFRs + 6,000 MW df/dt) but did not provide adequate relief. The blackout covered all eight Northern states and the Union Territory of Chandigarh; about 38,000 MW of NR load was lost. Restoration began immediately with start-up power from the surviving WR/ER and self-starting hydro at Uri, Salal, Chamera-1, Nathpa Jhakri, Karcham Wangtoo, Bhakra, Pong and Chibro/Khodri. ~40% of antecedent load was back by 10:00 IST and full restoration was achieved by 16:00 IST.

31 July 2012, 13:00 IST. A similar disturbance, this time taking down the Northern, Eastern and North-Eastern grids together — the larger of the two events, affecting ~48,000 MW of consumer load across 21 states and one Union Territory (around 620 million people, the largest blackout in history by population). Frequency before the incident was 49.84 Hz. Surviving zones included the Western Region, Narora Atomic Power Station, Anta/Dadri/Faridabad GPS, parts of the Delhi system, and Sterlite/IB TPS, Bokaro Steel and CESC Kolkata in ER. Start-up supply from the intact WR and SR plus self-starting hydro carried emergency loads (Railways, Metro, mines, airports) by ~15:30 IST and the system was fully restored by ~21:30 IST.

Contributing factors: skewed unscheduled interchange (~3,000 MW unscheduled export from WR, ~2,000 MW unscheduled import by NR) without an effective congestion-charge mechanism to mitigate it; the 220 kV underlying network became the load-bearing path once 400 kV elements were out, but was not visible to RLDC/NLDC operators because their data feeds froze on stale 1,000 MW values while the line was actually carrying ~1,450 MVA; under-frequency load-shedding relays did not act fast enough to stop frequency collapse; and the lack of effective islanding schemes meant the NR collapse propagated rather than separating cleanly.