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HindustanTimes Sat,20 Dec 2014

Grid-locked in the power corridor

Anupama Airy, Hindustan Times   August 07, 2012
First Published: 22:42 IST(7/8/2012) | Last Updated: 02:31 IST(8/8/2012)

In one of the biggest ever blackouts, a major power crisis was triggered in the country on July 31 across 20 states after three electricity grids — carrying about 55,000 mw — connecting these states and the national capital collapsed in the afternoon. The incident left over 640 million people powerless, that is half India’s total population, and was the second grid failure in less than 48 hours. Just a day prior on July 30, a major power failure had stuck the northern region in the early morning (2.30am), tripping power supplies in eight states, including Delhi, Haryana, Himachal Pradesh, Punjab, Uttar Pradesh, Uttrakhand, Jammu and Kashmir and Rajasthan, home to nearly 360 million people.
 
What is a power grid?
A power grid works in the manner similar to funnelling salt to small shaker from a large bag. Without the funnel, the salt will pour out. Likewise, power generated by plants usinghttp://www.hindustantimes.com/Images/Popup/2012/8/08_08_12-buss23.jpg various fuels such as coal, hydel, etc, flows to grids through transmission lines.

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How does a grid function?
Grids collect extra high voltage electricity from power generating stations and convert these into manageable voltage levels. This electricity is finally transported to final consumers by power distribution companies such as BSES and Tata Power in Delhi through power substations and transformers.

How many grids are there in India?
There are five power grids — northern, southern, western, eastern and north-eastern — carrying electricity from various power plants to respective regions and states across the country. All of them are inter-connected, except the southern grid.

What are RLDCs?
RLDCs or the regional load dispatch centres — a total of five, one being for each grid — act like the gatekeepers for the power drawing schedule.

What is a grid failure?
A grid failure is a tripping of the network of transmission lines carrying electricity load from the source (or a power plant) to the users that include state distribution companies. The disruption in carriage of electricity by these transmission lines causes power outages or blackout in areas that are supplied power through these lines.

What is the cause of a grid failure?
It is the overdrawing of power by states that leads to fluctuations and tripping of transmission lines carrying power load. Many states deviate from the drawn schedule. It is similar to a river that flows through many states where states keep on diverting water to their parched regions. Likewise, many states overdraw power from the grids leading to their collapse. This leads to fluctuations in the normal frequency (or the rate of change measured in cycles per second or Hertz) at which electricity is transmitted. Technical fault in transmission lines carrying power is another cause of a grid collapse.

What are 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.http://www.hindustantimes.com/Images/Popup/2012/8/08_08_12-buss23b.jpg

Why do states overdraw?
Overdrawing takes place mostly in summers when states have high requirement of power for meeting their agricultural needs. This year, due to late arrival of monsoons, heavy overdrawing from the grid resulted in a massive increase in load resulting into a failure.
 
What is the importance of northern grid?
With an installed capacity of 51,000 mw, this grid carries nearly 35,000 mw power every day across nine regions including Punjab, Haryana, Rajasthan, Delhi, Uttar Pradesh, Uttarakhand, Himachal Pradesh, J&K and Chandigarh and caters to about 28% of India’s population

How did the three grids — northern, eastern and north-eastern — collapsed at the same time?
As the three grids are connected, a tripping of lines in northern grid is believed to have a cascading effect on the other grids leading to a collapse of all three. Experts feel that sensors installed on these lines were faulty and led to simultaneous failure of grids.

What is the impact of grid collapse?
Life comes to a halt as essential services including hospitals, water supplies, local transport and railways were hit.
 
What do the two successive grid failures indicate?
The two successive massive grid failures raised serious concerns about India’s outdated transmission infrastructure as also the government’s inability to meet its huge appetite for energy as the country aspires to become a regional economic superpower. http://www.hindustantimes.com/Images/Popup/2012/8/08_08_12-buss23c.jpg
 
Have there been grid failures earlier?
In 2001, a major collapse of the northern grid was triggered following a failure of a sub-station in Uttar Pradesh; Restoration took at least 12 hours. Also in 2008 and 2010, the country saw minor tripping of the northern grid due to technical snags caused by fog in winters. Restoration took 3 to 4 hours.
 
How can we reduce the impact of a blackout on emergency services?
Islanding of states is a way to prevent such failures. Under the scheme, un-interupted supply can be maintained for essential services such as the railways, local metro, hospitals, airports and water systems across the country.


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