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Power grid failure: FAQs

Power supply across nine states of north India including Delhi, Haryana, Punjab and Uttar Pradesh was hit as the northern power transmission grid failed in early hours today.

delhi Updated: Jul 30, 2012 20:04 IST
Hindustan Times

What is a power grid failure?

A power grid is a tripping of the network of transmission lines carrying electricity load from the source (or a power plant) to the users that includes state distribution companies. Any disruption in carriage of electricity by these transmission lines causes power outages/blackout in an area. In India we have five regional grids (northern, southern, eastern, western and south-western) that carry electricity from various power plants to respective regions and states across the country.

What leads to a grid failure?

Over drawl of power from the grid by leads to fluctuations and tripping of transmission lines carrying power load. This leads to fluctuations in the normal frequency at which electricity is transmitted. Frequency is the rate of change measured in cycles per second or in a unit called Hertz.

What are considered as safe frequency levels?

A 50 Hertz frequency is considered ideal for maintaining grid discipline and a frequency variation in the range of 49.5 to 50.5 Hertz is permitted.

Why do states overdraw?

Mostly due to late arrival of monsoons, the load on the grid increases (due to paddy season in Haryana and Punjab) and states start over drawing to meet their agricultural needs.

Importance of Northern Grid: Carries nearly 35,000 mw power across nine regions including Punjab, Haryana, Rajasthan, Delhi, Uttar Pradesh, Uttarakhand, Himachal Pradesh, J&K and Chandigarh --- and caters to about 28% of the country's population

Impact of Grid Collapse:

Life came to a stand still and virtually all of northern India was blacked out for about 6-8 hours. Essential services including transport and water supplies ground to a halt in all the seven northern states.

Metro services across Delhi saw major impact and nearly all passenger trains in North India were affected including Shatabadi and Rajdhani running late. As many as 200 trains were running late across the northern region.

Traffic signals stop working – lead to chaos on streets. Metro passenger traffic diverted to roads. No flight disruptions at airports --- essential services at Delhi airport shifted to generator mode --- Delhi airport has a back up of 48 hrs of power supply.

While power supply to PM’s house, VVIP areas and major hospitals like AIIMS were immediately restored on priority from hydel generation. Also many other hospitals in small cities that were unable to function and where major surgery had to be cancelled.

Water supply broke down after treatment plants and pumping stations stopped functioning; millions of people were unable draw water from underground wells because the pumps were not working.

Major Grid collapses in India

2001: A major collapse of the northern grid that was triggered following a failure of a sub-station in Uttar Pradesh; Restoration took at least 12 hours.
2008 and 2010: Saw minor tripping of the northern due to technical snags caused by fog in winters of 2010 and 2008. Restoration took 3-4 hours.
2012: The worst collapse after the 2001 grid failure. A technical fault near Agra leads to a major northern grid collapse. Entire Northern India plunged into darkness for 6 to 8 hours

First Published: Jul 30, 2012 19:59 IST