Things appeared just normal as the night shift started on Sunday, 29th July 2012, at India's National load dispatch centre (NLD) in Delhi. A load dispatch center (or more appropriately, an Energy Management Centre) is a monitoring facility for an electrical power distribution system that can watch all the components of a power system such as generating stations, main distributing network and local distribution stations. Load dispatch centers usually monitor and control all these factors so that power system operates with good quality and security.
In India, the electrical distribution network or 'Grid” is divided into four regional grids, Northern, Western, Eastern and Southern Grids. Each of these grids have their own Load dispatch centers. Recently, all four regional grids have been interconnected and the nation wide grid is named as “NEW GRID'. We all know that electrical power is generated by Generators, which are essentially rotating machines, where rotation is caused either by steam turbines or gas or water turbines. The frequency of the AC supply we get in our houses, is nominally fixed at 50 Hertz. Any student of science would tell us that if the speed of rotation of the Generators slows down due to some reason or other, the supply frequency would also go down, creating havoc in the user networks. Load dispatch centers guard against this and keep a watch on the frequency.
Let me now return back to the night shift at National load dispatch centre at Delhi. The time is now 00.00 Hrs; UP, Punjab, Haryana states are slightly overdrawing the power, as a result, total Northern grid power requirement goes up. Load dispatch centre at Delhi, demands surplus power from western regional grid to counterbalances overdrawal and gets its. System stable with frequency remaiing at 50.46 Hertz.
Time 02.32 Hrs.
There is sudden spike in power demand from Northern grid to 35669 MW; as a result Western grid gets overloaded by about 1200 MW. Sensitive circuit breakers instantly trip off the 400KV single circuit line between Agra-Gwalior. As a result, northern grid gets isolated from western grid. With Overload disappearing, western grid continues normal operation. Northern grid, now under extremely heavy overdrawal, shifts demand to eastern grid. Unable to sustain this extra load, eastern grid isolates itself from northern grid as circuit breakers trip off the link between north and east; 400 kV Muzaffarpur-Gorakhpur line
Time 02.35 Hrs.
Unable to supply such heavy demand (35669 MW) on its own, because of heavy load-generation imbalance; northern region power supply frequency collapses. As a result, generating stations of the Northern grid with a total built in capacity of 24000 MW, start shutting down in a domino effect. It would require few more hours for the generating stations to restart. Entire Northern Region is engrossed in total darkness and without power except for
* 3 units at Badarpur TPS supplying part load in Delhi (approx 250 MW)
* Generating Unit at Narora with Simbhauli load (approx 100 MW)
* Part of Rajasthan system through Bhinmal (approx 100 MW)
Time 03.00 Hrs to morning of 30 th July 2012
Load dispatch centre at Delhi tries to to rectify the situation by extending power supply from eastern region by reconnecting 400 kV Muzaffarpur-Gorakhpur line at 0333 hrs, Pusauli A/C bypass line at 0351 hrs, 400 kV Pusauli-Sarnath line at 0457 hrs, 400 kV Pusauli-Allahabad line at 0530 hrs and power from Western region grid by connecting Vindhyachal A/C bypass line to Singrauli at 0453 hrs and finally ealier tripped 400 kV Gwalior-Agra line at 0545 hrs.
Some of the Northern Grid generating stations at Uri, Chamera I, re- start and start supplying power. However in spite of efforts to restart northern region base load stations in Dadri, Badarpur, Jhajjar by importing Start-up power from west, the Northern region is still largely without power as National capital New Delhi and about 300 Million people of North India wake up on Monday morning (30 July 2012) to find that their lives have come to a standstill.
The power outage plays havoc with the New Delhi's metro transit system's morning commuters. This system, which transports nearly two million passengers daily, grinds to a halt for several hours. The capital's throughways are even more jammed, as some of the metro passengers take their cars to work. Electrically powered intercity trains are stopped in their tracks or reach their destinations several hours late. At least 200 scheduled trains stand cancelled outright.
By mid morning, 60 percent of the usual power output in the eight northern states affected is restored by mid-morning, largely by drawing electricity from the eastern and western grids. According to press reports, by evening of 30thg July, Northern Grid is back to normal with power supply being fully restored.
As soon as Governments of Northern states woke up to the situation on Monday morning, the usual bureaucratic bungling began in earnest. India's power minister, Sushil Kumar Shinde said he had launched an investigation to determine the cause. Uttar Pradesh government removed Avnish Awasthi, chairman and managing director of the UP Power Corporation Ltd (UPPCL).
By Tuesday noon (31st July), the whole nation was jolted again to find that, what happened on Sunday night was not not an isolated incidence, as northern grid again collapsed at 13.00 Hrs with a small change in the menu. It also took along eastern grid down along with it. It seemed this time that the snag was in the eastern grid. Power supply to 19 Indian states was gone, which left 600 Million people without power again. Delhi Metro again came to a standstill. Most of the Generating stations of NTPC, National Thermal power corporation stand tripped off. For a watcher from outer space, the northern region of India must have looked like a black hole for two successive nights.
It has become obvious now that power distribution system in India needs some big overhaul to increase credibility and increase the confidence of the people in the system. Blackouts are frequent in many parts of India, but this was the worst the country has seen in a decade.
At local distribution levels, we witness extremely dangerous distribution networks consisting of open distribution boxes and cable ends, cables being run and connected in most unprofessional and incorrect manner. We are forced to pay price of lethargy of local state electricity boards in form of frequent blackouts and regularly happening fatal accidents. It now appears that the rot is spreading upwards to the higher level also.
Time has come to take a long and hard look at the way electricity is distributed in India. The first analysis shows that the grid collapse on two sussesive days was a result of the overdrawal of power mainly from two states; Harayana and Uttar Pradesh. The problem however is not so simple. These states have been drawing excess power to run the pump sets which supplies tube wells water to standing crops, mainly rice. It is therefore just not possible to cut off power to these states, which would surely affect the food grain production of the country. A better management of the available power needs to be done taking into consideration extra demand of power by these states. Some measures like cutting off power to non essential consumers can also be considered. If this is not done promptly, there are chances that the Northern grid may see repeat performance of last two days during current month also.
1 August 2012